Safe electric wiring

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Safe electric wiring/ household 120-240 Volt
Safe electric wiring means
1) People are not endangered or harmed
2) The work meets safe electric practice and never creates a future hazard
How to wire commercial 3-phase

2023

Safety
Multimeter Connect multimeter leads to wood sticks. Keep hands away from power. Test for breaks in wire or Test for voltage, amperage, resistance etc. Voltage is tested across two separate wires. Ohms is tested across both ends of same wire. Amperage is tested along two points on same wire. Typical appliance and electronics require 80% rated voltage to function correctly. Long runs of wire that exceed 100-150' cause voltage drop. Malfunctioning electric service can cause voltage drop on both Hot wires or either Hot wire. Multimeter is essential for testing AC and DC. Set to ohms to test resistance or continuity. Set to voltage, up to 600V. 600 volts is maximum service voltage found in some commercial installation, but never inside home or living area. Analog multimeter is easiest to use and cheapest, but less precise, and fewer functions, than digital multimeter. Buy Analog multimeter Multimeters at Amazon Klein multimeter Electric testers at Amazon Clampmeter for testing amp flow on line Resources: How to test and replace element How to test thermocouple Element tests for 120 volts How to test wire	Basic risk: 100s of deaths and 1000s injuries per year. 'Fire and shock are the only known hazards from electrical wiring. Electrical installations are 3rd leading cause of household fires behind candles and cooking, followed by heating and smoking.' Malfunctioning equipment, deteriorated or damaged installation, incorrect wiring, loose wires and boxes and covers, missing covers, wrong amp rating on devices and wires and breakers, missing ground wire, improper ground ... increase hazard. Safety Never touch wet or previously flooded appliance. Never stand on wet surface when working on electric. Never stand on bare soil, put down dry boards. Use non-contact voltage tester before touching wires. Never touch or lean into anything made of metal. Remove metal objects from pockets. Do not use oxygen or fuel accelerants in same room as electrical repairs Human contact with electricity Dry skin is a poor conductor, but inside body is water and salt, which are good conductors. There is a small difference from slight shock to death. Threshold of perception to 60 Hz AC between major extremities - 0.5mA-1mA . 5mA slight shock, most people can let go. 5mA-30mA painful, lost of muscle control. Respiratory paralysis - 30 mA . Heart dysfunction - 75 mA. 50-150mA Respiratory arrest. Cannot let go. 1000-4300 mA heart ceases, nerve damage. 10,000 mA severe burns, skin surface breaks Hazardous potential threshold, skin contact - 40 V. Skin contact resistance - 1K-5K depending upon conditions. Body resistance between major extremities - 500 ohms (exclusive of skin). Skin effects disappear as voltage increases, higher potentials being able to pierce the skin's protective layer, causing more penetration. Electrical burn... turn off power ... do not apply water ... call emergency ... lay person on side ... resuscitate Resource: What causes electrocution
Cord lock ... for weather-resistant extension cord connections Buy: Water-tight cord lock Note ; Weather-resistant means water can penetrate. Waterproof means no water can penetrate. Humidity and moisture can be present inside either type. Insulated lever switch on outdoor lights Operate outdoor toggle switch safely ... and easily Replaces outdoor cover. Install over top of ordinary toggle switch. Works with single-pole, double-pole, 3PST, 3-way, 4-way switches etc. Buy: Cantex lever switch Leviton lever switch Outdoor lever switches at Amazon Weather resistant plastic box for outdoor extension cord connections, Christmas light controls, power strip etc . Not for connecting wires with wire nuts, or permanent in-wall wiring. \can be used indoors to organize extension cord connections etc. Buy: Large-medium-small electric cord box Socketbox Raintight enclosures	120 volt 15 amp devices including GFCI, timers, switches, plugs can be installed on 15 or 20 amp breaker. 120 volt GFCI that are rated 20 amp can be installed on 20 amp breaker only, but NOT on 15 amp breaker. Buy 15 amp GFCI 20 amp GFCI GFCI must be installed in Bathroom ,,,,, kitchen.....laundry room..... unfinished basement.... crawlspace.... garage wall outlets,.... outdoor outlets... any place you can come into contact with both voltage and water, or voltage and ground (earth). 240 volt GFCI breakers are installed inside breaker box (service panel) Using 120 volt GFCI breaker is good option instead of wall outlets GFCI ... except more difficult to replace, and less accessible for testing. Caution: just 1 GFCI per circuit to ensure correct function. Multiple GFCI on same circuit can cause frequent resets and failures. For permanently wired GFCI (breakers and outlets), a monthly test is recommended. Press test button on GFCI to simulate fault condition. Reset ensures the device is functioning. **Portable type GFCI's (used for temporary swimming pools, onsite extension cords etc) should be tested each time before use. Some devices like power vented water heaters, and other electronic devices specify no GFCI ... a GFCI can cause error codes or malfunction on devices that use ground wire as functioning part of electronic control. Resource: How to wire GFCI GFCI will not reset Portable GFCI
Where electricity comes from and how it gets to home Resources See inside main breaker box What is 3-phase Difference between single-phase and 3-phase What causes electrocution	Use nipper instead of pliers or screwdriver for removing staples (and nails). Do not damage wire. Damaged wire is fire risk, and can cause circuit breaker tripping, and be difficult to locate. If staple or nail has cut into cable, carefully inspect wire to see if the wire insulation has been pierced. Wire may need to be replaced, or tape added over damage. Best to replace wire. Code -Cable SHALL BE secured without damage to the outer covering. NEC sec. 336-15 Buy End cutting nippers at Amazon

Electricity is a combination of voltage and amperage.
Volts x Amps = Watts (power consumed)
Voltage is measured as a potential across two different wires. Household voltage remains relatively steady at all times, except for brief surge events.
Amperage is measured as a flow of current along a wire. Amperage rises and falls with usage, with more amperage flowing on the wire when appliances are turned on. Buy: Clampmeter for testing amp flow on line

How it works:
Voltage is the force that pushes amperage (current of electrons) across and through the matrix (atomic structure) of a conductor (wire). The conductor always offers resistance (measured in ohms) to the current of amperage. Resistance is like friction, so when too much amperage is being pushed down a wire because of undersized wire or short circuit (fault), then the wire begins to get hot, melt and catch fire. The circuit breaker (overcurrent protection) responds by tripping off the power.

The circuit breaker responds to amperage, not voltage.
It does not respond to ordinary household voltage spikes, but a breaker can trip if lightning strike energizes the wire with enough voltage. For voltage spikes, a surge protector is used.

The breaker is a thermal-magnetic device that works two ways.
1) It responds slowly to thermal events (heat on the wire) caused by a circuit drawing too many amps, like too many appliances running.
2) It responds immediately to a short circuit (ground fault/ insulation failure). The sudden rush of amperage will energize a magnetic coil insde breaker that will cause it to trip immediately.
Once the breaker trips, the overcurrent event caused by overload or by short circuit is stopped.

Ground wire
The breaker trips 'immediately' when overamperage is a sudden event, but not as quickly as GFCI, nor as quick as a ground wire. The overcurrent from a short circuit starts running into the ground wire first, which helps protect the breaker and wires by redirecting as many electrons as possible into the ground rod and earth.

Because the breaker does not trip instantly, a fault current poses hazard to anyone coming into contact with live electricity. This problem is mitigated by installing GFCI, but also by properly grounding all circuits, metal boxes etc, never using ground wire as a Neutral etc. How to wire GFCI

Never assume electricity is OFF
Power safety:
120 volts AC is the most common voltage, and most common killer.

Turn power off
All electricity is attracted to ground (earth). If you're standing on bare soil or touching anything that is grounded, you are giving electricity a direct route to earth.
Do not touch electrical equipment unless power is off.
Install GFCI on kitchen, bathroom, basement, laundry room, garage, attic, and outdoor outlets. How to wire GFCI
Use 3-prong grounded tools and equipment. Do not cut off the ground prong.
Never stand in water or wet surface when around electricity
Never stand on bare soil. Stand on dry boards.

Electricians use fiberglass ladder. How to climb on roof
Do not touch or lean into anything made of metal when working on electricity. Remove metal from pockets. Do not hold metal tools in mouth.
Install safety switch, or pull-out cut off on HVAC and any machine or electrical appliance where electrical breaker panel is not in direct sight line. How to wire safety switch

Use non-contact voltage tester on timer, wire, outlet, switch, motor etc to see if power is present.

Tape tester leads to wood sticks, never touch wet water heater (or appliance, timer, motor), or flooded water heater that had a short or fire without turning power OFF.

Buy:
Analog multimeter
Multimeters at Amazon
Buy non-contact voltage tester at Amazon
fiberglass ladder
Resources:
How to wire GFCI
Wire connectors

When adding to a circuit
Step #1 Identify circuit breaker and all outlets, lights, appliances etc on circuit (branch circuit). The maximum number of boxes on one breaker is 12. See image Step #2 Find total amp load. Add up total wattage being used on that breaker, check if breaker is 120 volt or 240 volt. Then divide total watts by volts to get the amp load being drawn from that breaker. Example a) a 240 volt circuit with 1 Hp motor is using 800 watts approximately. Divide 800 watts by 240 volts = 3.3 amps. Motor loads are inductive load, so they draw brief surge of amps during start up. Allow a bit more amps for motor loads like pumps, shop tools, HVAC and window air conditioners etc. Example b) 120 volt bedroom circuit has a TV, ceiling fan, heating pad, humidifier, and several lights. The total wattage might be 900 watts. Divide 900 watts by 120 volt = 7.5 amps. If the circuit has a 15 amp single breaker, the safe maximum for 15 amp breaker is 80% rated value or 12 amps. The maximum for adding a new load is 480 watts or 4 amps. If the circuit has 20 amp breaker with 80% safe maximum 16 amps, then the maximum new load is 1020 watts or 8 amps. Example c) New refrigerator in garage. Refrigerator label shows 115 volt (120 V) and 6.5 amps. The garage door opener draws 4 amps, the lights 2 amps, the dehumidifier 2 amps, shop vac 4 amps, the work-bench TV 3 amps = 15 amps total. The 6 amp refrigerator brings total to 21 amps. This exceeds 20 amp breaker safe maximum of 16 amps. ....... But the shop vac, humidifier, TV and garage door opener are not used all the time. The circuit might work. Or you might need to add another circuit from breaker box. Resources How to replace circuit breaker Not enough space in breaker box How to add another outlet How to replace outlet with combination switch How to add 3-way switch Total amps on circuit should not exceed 80% of breaker amp rating. Do NOT add a larger amp breaker. The circuit breaker and wire size must match. Install tandem breaker if there are not enough spaces. Install a new breaker with correct size wire to match breaker. See image
When repairing circuit or replacing device
Check the rating of any defective or new device and compare with total load (all watts being used on the circuit). Read the product manual, and check product label. Some devices, like dimmers, timers etc might NOT be rated for inductive loads like LEDs or motors, or work with fluorescent loads. Check the voltage rating on each device, appliance etc. Do not install 120 volt device on 240 volt circuit. Do not install 240 volt device on 120 volt circuit. Appliances are often rated 115-125 volt. That rating means 120 volt. The actual voltage varies by service ... so 240 volt might test 236 or 250 volts. Anything less than 80% rated value can cause malfunction of appliance. Low voltage and voltage spikes (surge) can harm motors. Install voltage monitor that turns off motor if the voltage drops. Resources: Voltage monitor Surge protection Check the wattage rating of device. If dimmer is rated maximum 600 watt incandescent, and you have 1200 watts of bulbs, then it is not the correct dimmer. Using it poses a fire risk. Option: change to LED bulbs that consume much less wattage and select dimmer rated for LED. Resources: How to wire switches How to wire 240 volt outlets/ plugs
Short circuits or ground faults can be hard to locate if there is no obvious damage. 1) Unplug all appliances and devices, turn off ceiling fans etc and see if breaker resets 2) Open each box on circuit, and use nose and eyes to inspect for fire damage, melting. 3) Check for loose wire or loose wire connector. Look for burns, charring, or smell of burning. 4) rodent damage can be concealed behind wall, and is high risk for fire. 5) check for aluminum wire, and call electrician if found. Most shorts are caused by movement. Electrical must be attached firmly to structure, wires attached tightly to boxes and devices, and protected from damage by equipment etc. Keep belongings away from electrical. Replace with better-quality switches, timers, outlets, pumps, fans etc. Resource: How to find short circuit (ground fault) Short circuit between Hot and ground causes breaker to trip, and can be found using steps above. Contact between Neutral and ground is a 'grounded Neutral' which has risk of electrocution but does not trip breaker. Do not use Neutral as ground, or ground wire as Neutral. Resource: Test for grounded Neutral Resources: Water heater trips circuit breaker Troubleshoot household electricity
When replacing a device such as switch outlet etc. All electrical devices come with markings. Most electrical devices come with instruction sheets or illustrations (except cheap bulk sold switches etc). Look for marking and label on devices to identify the correct voltage and power (watts) demand needed to operate. Look for volts and watts printed on each electric device. 115 to 125 V volt is considered typical rating for most devices used on 120 volt circuit. 15 amp switch, outlet, dimmer, home automation etc can handle safe maximum 12 amps (15 x 80% = 12), or 1/2 HP. 20 amp device safe maximum 16 amps, or 1 HP. 30 amp device can handle safe maximum 24 amps (30 amp x 80% = 24 amps) Always refer to product instructions first. Don't guess. ALWAYS connect ground wire to green screw. Resources: How to wire switches How to replace circuit breaker Not enough space in breaker box Buy: 30 amp 2-pole switch 30 amp industrial grade

Code
NEC (National electric code) 120 volt devices including GFCI, timers, switches, plugs, outlets, dimmer, home automation etc

120 volt 30 amp outlet can be installed on 30 amp breaker only/ use 10 gauge wire
120 volt 20 amp outlet can be installed on 20 amp breaker, but not 15 amp breaker/ use 12 ga wire
120 volt 15 amp outlet, AFCI, GFCI, timer, switch etc can be installed on 15 or 20 amp breaker
Wire size must match breaker rating, and device terminals rated for wire size

This means if you have switch rated 15 amp, and the breaker is 20 amp, then it's good... as long as wire size is 12 gauge to match circuit breaker... and good because 12 gauge wire will fit screw terminals on 15A switch.
Resources
Match wire and breaker size
Code for switches

NEC (National electric code) 240 volt outlets

240 volt 50 amp outlet can be installed on 50 amp breaker only/ use 6 or 8 ga wire
240 volt 40 amp outlet can be installed on 40 or 50 amp only
240 volt 30 amp outlet can be installed on 30 amp breaker only/ use 10 gauge wire
240 volt 20 amp outlet can be installed on 20 amp breaker, not 15 amp breaker
240 volt 15 amp outlet can be installed on 15 or 20 amp breaker
Wire size must match breaker rating, and outlet terminals rated for wire size

Buy:
NEC books
Dewalt plumbing/ electrical codes
Basic electric book
National electric code guide

NEC is one of 300 codes, standards and recommended practices.

Rating label/ Small appliances

Look at the rating label
Devices that consume electricity (refrigerator, water heater, computer, light bulb, microwave etc) each have a rating label.
The label shows volts and watts, and sometimes shows amps.
Divide watts by volts to find amps.
For example 100 watt light bulb divided by 120 volts = .8 amps for each 100 watt bulb.
Or 60 watt light bulb divided by 120 volts = .5 amps.
If you have five 60 watt bulbs, then .5 watts each x 5 bulbs = 2.5 amps.

Look at watt rating of small appliances before buying.
1500 watt microwave, or tea kettle or space heater will consume 12.5 amps (1500 watts divided by 120 volts = 12.5 amps).
Using 20 amp breaker and 12 gauge wire with 80% safe maximum of 16 amps is correct choice for 1500 watt small appliance. The 20 amp breaker will easily support a 1500 watt, 12.5 amp microwave or other small appliance ... but the breaker will not support additional appliances or loads like a refrigerator that consumes 7-8 amps.
If circuits are overloaded, choose 1000 or 1200 watt small appliances instead of 1500 watt.

Plug small appliance into Volt-Amp-Watt meter
Photo on right shows toaster plugged into a meter. The meter is temporary since small appliances like the toaster should be plugged directly into outlet for highest level of safety, and not plugged into extension cord etc. Meter shows 7.04 amps, and we know the outlet is 120 volts ... multiply 7A x 120V = 840 watts.
Buy
Electric meter
Cuisinart CPT-122 toaster
Toasters

Dedicated circuit

Larger image
Dedicated 120 volt circuit serves only 1 Load
Dedicated means the circuit breaker supplies power to one outlet or load, and no other outlet or load is connected to the circuit.

Small appliances
For example, by code, a microwave oven requires ‘dedicated’ breaker that supplies power to a single outlet where the microwave is located ,,,,
The mathematics shows why. The typical 120 volt 1500 watt microwave oven uses 12.5 amps. (1500 watt divided by 120 volt = 12.5 amps)
A 1500 watt microwave pulls too much amperage for 15 amp breaker. The 80% safe maximum for 15 amp breaker is 12 amps. (15 amp x .80 = 12 amp). Choose 1000 watt or 1200 watt microwave instead of 1500 watt.
20 amp breaker is good for any small appliance up to 1500 watt. 80% safe maximum for 20 amp breaker is 16 amps. (20 amp x .80 = 16 amp). So 1500 watt microwave consumes so much amperage on a 20 amp circuit, that other loads might not operate at same time without overloading circuit.

To solve the problem of using 15 or 20 amp breaker for dedicated circuits, modern code requires 20 amp dedicated breaker for microwaves, but also lets older homes keep 15 amp wiring if local codes approve, and if electrical changes are not included in a remodel.
Remember, older homes had safe wiring when installed, and will generally still be safe today (assuming structure is solid .. and wiring has not been exposed to high heat, wetness, incorrect wiring additions, rodent damage, plus copper wire was used and not aluminum etc), but wiring in older homes might not supply amount of power needed for modern consumption.

Dedicated 240 volt circuits
-240 volt loads, like Clothes Dryer, water heater, oven, HVAC etc are on a dedicated breaker that serves no other 240 volt load. The reason is the voltage is high and the appliance usually draws near-maximum amperage from the breaker.
-For example 240 volt 4500 watt residential water heater consumes 18.75 amps, requiring a 30 amp breaker with safe maximum 24 amps .... which leaves an extra 5.25 amps. (24 amps minus 18.75 = 5.25)

-Since the circuit has extra 5.25 amp capacity, it is ok to hardwire a small-watt device like a timer, indicator light, voltage monitor, wifi device, hour meter, transformer, contactor etc into the circuit. (Hardwire means the device is not a plug-in module, but is attached into the wiring)

Other dedicated circuits
Other household items might recommend dedicated circuit breaker. For example and flue-dampered water heaters that plug into outlet. These water heaters only consume a few amps, but the electronic gas control valve is susceptible to surge and line noise that result from other loads on same breaker. For example a motor load will cause voltage surge events that can adversely affect electronics.

Power-vent and flue-dampered water heaters benefit from a surge outlet. All electronics should have surge protection.
Multiple surge devices on one circuit are fine. The closer the protection is located to electronics, the better it protects.
Correct polarity and grounding are required for Type 3 surge outlets and surge protection strips so they can work correctly by 'jumping the gap' to ground.
Footnote: Power vented water heater manuals say no GFCI because it causes error codes on the gas valve.
If electronics continually reset or throw error codes: install noise filter, and check polarity and grounding of outlets using circuit analyzer.

Buy:
15 amp surge suppressor receptacle
20 amp Surge outlet
15 amp duplex surge protector with indicator
20 amp industrial grade surge protector
Outlet tester for polarity
Resource
Surge outlet manual

Appliance Safety:
''• Only use one heat-producing appliance (such as a coffee maker, toaster, wok, space heater, clothes iron etc.) plugged into a receptacle outlet at a time.
• Major appliances (refrigerators, dryers, washers, stoves, air conditioners, water heater, microwave ovens, etc.) should be plugged directly into a wall receptacle outlet. Extension cords should not be used.''
Do not plug larger loads such as appliances into a timer or wifi module etc. Exception: A wattage monitor can be added for a few days, but loose plug-in connections risks spark and short that can damage appliance electronics. A loose connection causes more heat, and will weaken eleectic outlets, and loosen the contact points, leading to further deterioration (damage) over time.
Deteriorated electrical installations are a main cause of electrical problems, short circuit, fire etc.

'Small appliance branch circuit is a circuit that supplies power to receptacles in kitchen, dining, and laundry where small appliances are used. These circuits must be 20 amp, and wired with 12 gauge cable.' Code: Kitchen counter outlets require 2 small appliance branch circuits.

What if you have 15 amp circuit for the kitchen instead of 20 amp as required by code?
The 15 amp breaker does not meet updated code requirement for 20 amp small appliance circuit.
However if home has 15 amp breaker, do not panic and replace the 15 amp breaker with 20 amp unless the wire is 12 gauge.
The 15 amp breaker will trip if more than one appliance is running at same time. So stagger use of countertop appliances and consider adding a dedicated 20 amp circuit.

If appliances are continuously operated, then code requires strict adherence to the 80% rule, and 20 amp circuit is required for that appliance.
A continuously operating load, particularly motors (refrigerator, pool pump, window air conditioner) will cause wire to get warm and then cool and then get warm again next time load turns on. This causes expansion and contraction, wear and tear on breakers and connections. By following the 80% rule, heat stays within safe limits so electrical installation doesn't deteriorate over the long run.

Amp rating for outlet (receptacle), plug and connector

Recognize difference 15 and 20 amp 120 volt

Each switch, plug and electrical device is marked with a volt and amp rating.
120 volt Outlets have a profile that shows amp rating. 120 volt plugs will fit either 15 or 20 amp outlet.

For 240 volt plugs, outlets and connectors are typically rated 250 volt, and vary by amp rating. Because 240 volts delivers so much power (wattage), the higher amp ratings 30, 40, 50, 60 amp plugs and outlets are larger size.
Resources for 240 volt:
How to wire 240 volt outlets
How to wire twist lock plugs
Basic house wiring

Recognize difference 15 and 20 amp 240 volt
National electric code for 240 volt outlets:
NEC says if the window air conditioner is rated 20 amps, then the breaker MUST be rated 240 volt 20 amp, and the outlet and plug rated 20 amp.
If the window air conditioner is rated 15 amp, then the breaker can be 15 or 20 amp ... but the outlet and plug must be rated 15 amp.
A 50 amp 240 volt plug cannot be used on 15, 20, or 30 amp breaker ... the breaker must be rated 50 amp for all 50 amp 240 volt plugs.

Note: the 240 volt 15 amp plug will fit into the 20 amp outlet, but the 20 amp plug will not fit into the 15 amp outlet.

Buy 15-20 amp:
6-15P 240 volt 15 amp plug
6-20P 240 volt 20 amp plug

Buy 15-20 amp:
15 amp 6-15R connector
20 amp 6-20R connector

'Common-feed' outlets/ receptacles
A single 120 volt line from breaker supplies power for both 120 volt receptacles, with mixture of straight-blade and 1 twist-lock blade.

For twist-lock devices,
Image on left shows L5-15 twist lock and 5-15R straight blade outlets wired in parallel. All electrical wiring is parallel as shown, where each 120V outlet receives a Hot wire, Neutral and ground.
Buy: 4792/ 15 amp 125 volt twist lock and straight
L5-15R outlet
L5-15P twist lock plug 15 amp
L5-20P twist lock plug for 20 amp

Twist lock outlets, connectors and plugs are used where power outage or poor connection pose risk ... for example breathing machine, meat freezer, stage lighting etc. Twist lock plugs,, connectors and outlets are made for a variety of household, business and commercial voltages and amperage ratings, including commercial 3-phase. Resource: How to wire twist lock plugs

Screw color
Black Hot wire always connects to brass or black screws. White Neutral to silver screws. Ground to green. Always connect ground wire. A continuous ground wire must connected all devices, metal boxes and conduit back to main breaker box, and then to ground rod. Ground is required for safety.

Typically, each double outlet has two bonded (joined) screw terminals for Hot, and two joined terminals for Neutral. and 1 green screw for ground.
Maximum 1 wires per screw terminal. Wires can be hooked onto a screw, or looped around screw. For 2-3 wires, it is best to connect all 3 together with twist-on wire connector, then run a jumper (short length of wire) to the screw terminal, or use the quick-connection (small hole located on back of device) if available. Higher amp devices generally do not have quick connections to ensure reliability during high amp and heat of a full load.
Quick connections can be released using small screwdriver See quick connection images

On the Hot side of straight-blade outlets and combination switch-outlets, the two terminals are bonded together with a removable piece of metal called break-away fin. The break-away fin can be removed with pliers or cutters to isolate upper and lower outlets on a duplex device. This can be done to accomplish different wiring objectives.

Max amperage on 15 amp circuit is 12 amp total, no matter how many 15 amp outlets are available on circuit.
A 15 amp outlet has 2 places to plug 15 amp loads, but the maximum total safe amperage for both outlets together is 12 amps. Safe maximum for total circuit with multiple 15 amp outlets is 12 amps.
Safe max amperage on 12 gauge wire, WITH 20 Amp circuit breaker, 20 amps x 80% = 16 amps total.

Switches
Switch-outlet combos require a Neutral wire and are often used to replace ordinary outlet or switch. Wiring It is code to turn off the Hot wire in a 120 volt circuit. It is not code to turn off the Neutral wire, unless Hot is also turned off using a double pole switch. Buy: Combination switch outlet Resources: How to wire Combo switches How to replace outlet with combo switch	Pilot light switches and outlets are used to indicate when a circuit is ON or when a device has power. Buy: Leviton pilot light switches Resources: How to wire pilot light switch Amp rating of devices It is acceptable to use 15 Amp device on a 20 Amp circuit. Using 20 Amp switch or outlet on a 15 Amp circuit is potentially dangerous.	Switches are connected to Hot wires only. Neutral wire only connects to combination and pilot switches, but not to single, double, triple switches. Each switch has amp and voltage rating ranging from 15 to 40 amp, with voltage range 120 to 277 volt. Resources: How to wire switches How to add a switch How to add a 3-way switch How to wire safety switches How to wire occupancy switch How to wire transfer switch How to wire door switch Control motor with two switches

Wiring 120 volt switch Each 120 volt switch box must have a Hot wire, White Neutral, and gound wire present in the box. By code, a White wire CANNOT be used to carry voltage in 120 volt circuit. The White Neutral cannot be used for a ground wire. The ground wire cannot be used as a Neutral. A neutral wire is never switched. With any type of switch, only the energized or Hot wire (conductor) should be switched. "Never place a switch within a neutral conductor’s path." Neutral wires are twisted tightly together, covered with wire nut® and pushed to back of box. The ground wire must be connected to switch on the green screw. Before pushing Neutral wies to back of box, twist all ground wires together and push down and away from wiring terminals on switch. Best if grounds are twisted together and wire nut applied. Most single-pole switches are rated 120-277 volt as printed on switch. Cheapo box store switches are rated 120 volt, and are used for 120 volt only. Connection and switch must be inside approved electric box with cover that fits flush over switch box. Resources: Steps for replacing typical switch How to troubleshoot loose wire, ground fault, or short How to wire switches How to wire combination switch outlet Wiring 240 volt switch All double-pole switches (with 4 screws + ground screw) are rated for 240 volt. A 240 volt circuit has 2 hot wires.... 240 volt circuits do not require Neutral wire, but require ground wire. For 240 volt, it is OK to switch either one or both of the hot wires. A single-pole switch rated for 120 volts can NOT be used to switch 240V. A single-pole switch rated 120-277 volt can be used to safely switch 240 volt, because 240 volt is less than 277, but would not adhere to strict code, depending on local codes and enforcement. For long-term, best to use 30-40 amp switch. Safe maximum: switches, plugs, breakers, connectors, wires etc have a safe max amps. 30 amp switch safe maximum 24 amps: 240 volts x 24 amps = 2760 watts Buy: 30 amp double-pole 240 volt motor switch 40 amp double pole 240 volt motor switch 30 amp 2-pole switch 30 amp industrial grade Resources: How to wire switches Control 240 volt water heater with single-pole and double-pole switches
Safety switches are used to isolate appliances and other equipment such as shop tools, HVAC, water heaters etc. Buy: 2-pole outdoor / 60 amp/ non fusible/ 2-pole indoor / 30 amp/ fusible Safety switch should be installed within eyesight of the appliance so power cannot be accidently turned on while electric work or repairs are performed. Safety switches are required by code for all HVAC and PV solar panel installations, and can be required for specific installations, like tankless electric heaters, depending on local codes. Safety switches come in both indoor and outdoor varieties, both fusible and non-fusible. Safe switch can be installed optionally on any circuit, for example water heater. A circuit can have multiple breakers, fuses, switches, cut-offs etc without problem. Resource: How to wire transfer switch	Transfer switch Buy 510 series 50 amp Reliance 30 amp Any AC generator that is used for backup power and is connected into main breaker box or feeding power into breaker box, must be isolated from the grid by turning off main breaker or installing transfer switch. Code require transfer switch. Failure to properly isolate the electricity from the generator can cause injury or death to electric utility workers, due to backfeed of electrical energy from the breaker box into the grid transformer and then out onto the grid wires at high voltage Resource: How to wire transfer switch
Contactors and relays are types of switches ... used for heavy amp loads, and loads the are switched frequently. Open frame relay shown. Rated for more operations and high heat, they are requirement for many types of circuits. Resource: Contactors and relays How to wire open frame relay	Timers are a type of switch Information on this page covers basic wiring safety for all devices including timers. Timers come in wide variety of Amp , Volt and Load ratings. Use search feature at top of page to locate wiring diagrams, manuals. etc. Resource: How to wire Box timers

Circuit breakers
	Turn off circuit breaker before working on electric wiring Maximum 12 boxes per circuit 240 volt must be a connected double-breaker. It is ok for a circuit to have multiple breakers and fuses as long as each matches amp rating of breaker and wire size. Resources: How to replace circuit breaker How to wire gfci Match breaker and wire size See inside breaker box Not enough space in breaker box
	Circuit breakers are rated by amps Breakers are safe for any voltage. 240 volt must be a connected double-breaker Types of breakers include: Single breaker for 120 volt Double breaker for 240 volt Tandem breaker to add more breaker space GFCI breaker for vulnerable circuits Resources Tandem breakers How to wire GFCI breaker Are both sides of 30 amp double breaker 30 amp
Code says: Use connected/ double-pole breaker A double breaker can be used for 2 separate 120 volt circuits. Against code: Use 2 single breakers to supply 240 volt, unless the switches are connected and rated for same amps. If breakers are connected, then if one side (leg) trips the other side usually trips off too. If breakers are NOT connected, then one leg might be tripped, and other leg not tripped. A double breaker that is tripped on one leg poses a threat if working on the circuit. Never assume power is OFF. To reset, push fully off then back on. If double breaker is rated for 30 amp, then BOTH sides of the breaker are each 30 amp (not 15 each) Power is doubled with 240 volt vs 120 volt, amps are not halved. Resource: 240 volt breaker keeps tripping

Push down

1" wide Push down breaker
Plug-in breaker
Buy single-pole:
Choose from 15 to 60 amp
Eaton CL series
Siemens 15-60 amp

Single-pole tandem breaker
Tandem breakers

Push down

2" wide Push down breaker
Plug-in breakers
Buy double-pole:
Choose from 15 to 125 amp
Choose from 15 amp to 200 amp
Eaton CL series circuit breaker
Siemens circuit breaker
Double pole GFCI

120 Volt and 240 Volt breakers -Image shows 120 Volt line and 240 Volt breakers inside residential main panel or breaker box. -All circuits have ground wire. -Both 120 and 240 require two wires to complete circuit. -120V requires 1 hot and 1 neutral -240V requires 2 hots from different busbars. -Ground wires are for safety. Resources: Read more about 240 volt Why you need ground wire -Neutral not necessary to complete 240Volt circuit. However some 240Volt lines have additional neutral wire. However, -240Volt lines can be white and black or red and black -Modern breaker boxes have separate Neutral and Ground busbars that are bonded together electrically. Older boxes often have one busbar for both Neutral and Ground. -Illustration shows Neutral and Ground busbars on same side of box so it is easier to illustrate wires. In actual box, the Neutral and Ground busbars are on opposite sides. Resources: Color code and wire sizes Larger image
Main breaker wires are HOT when main breaker is OFF unless meter is pulled When working inside main breaker box, the lugs on main breaker are Hot all the time, even when main breaker is turned OFF. Absolute electrocution danger when removing cover off main panel. How to pull meter
Wires
	Add black tape when White wire carries voltage (applies to 208 and 240V circuits) With 120 and 277 Volt circuits, White wire is Neutral, and Black is Hot With 208 and 240 circuits, both wires are Hot, and both wires carry voltage Black tape on White wire identifies wire is Hot and not Neutral Wires for 240 volt can be Red-Black but are usually White-Black " a white wire is allowed to be used as an energized conductor as long as is marked with a black band to indicate that it is an energized conductor.
	Aluminum wire is a danger/ Use only copper wire. If you encounter aluminum wiring ... a professional electrician MUST be called. Do not assume copper and aluminum wire are the same, or interchangeable. Aluminum wiring is a FIRE hazard. Code says: Only devices marked CO/AIR can be used with aluminum wire. Do not use aluminum wire: fire hazard unless installed professionally using AL-rated connections. All wires have resistance to electric current. Resistance is like friction that causes heat on wire. Wire expands when it gets warm/hot. Aluminum and copper expand at different rates. Aluminum expands a lot more than copper, and will force wires and connections to come loose from terminals, wire nuts etc
How to test for 120 volt Hot and Neutral wire: 120 volt circuits have 1 Hot, 1 Neutral and 1 Ground. Find the Hot wire first... every 120 volt box has 1 Hot wire, thereby just one circuit breaker supplies power to wiring inside box. It is against code to have hot wires from 2 different breakers inside the same box. It is against code to have 2 different voltages inside same box ... for example household voltage, and low voltage doorbell wires, or media cables. Different voltages must be separated into different boxes or have approved barrier to prevent energizing low voltage wires with house voltage. Exception: a control box with indicator light, etc. when box is completely covered. Identify breaker that supplies power to box. Turn power off. Use non-contact voltage tester to confirm power is off. Separate all wires for testing except ground wires. Turn power on. Tape tester leads to wood sticks for safety. Keep hands away from power. Test the black and white wires to bare ground wire. Hot wire should be black (except 3-way switches). White wire should not carry voltage or be Hot in 120 volt circuit. Tester lights up on Black Hot wire to ground. Only 1 Black wire is the Hot wire. Other black wires can be in the box, but only 1 is the Hot wire from breaker. Tester does not light up on white Neutral to ground. Next, test Hot wire to all other wires except ground. Tester lights up when Hot is tested to Neutral wire. How to test for 240 volt Same as above: separate wire for testing. Test all wires to ground. If mo0re than 1 wire lights up when tested to ground, the voltage is 240V. If only one of the two wires light up when tested to ground, the voltage is 120V. Tester will not light up when Neutral is tested to ground. Buy: Voltage neon testers at Amazon Electric testers at Amazon
Use only 600 volt SOLID copper wire for household wiring DO NOT USE STRANDED WIRE for 14-10 gauge wire Larger wires, 6-8 gauge and larger gauge wires, are stranded, and typically have lug connection. Rolls of 12 gauge 600 volt stranded wire at local box store seem inviting, and have wide choice of colors, but are not best choice for screw terminals, like found on switches, outlets, breakers ... because stranded wire comes loose with the heat from a load, and loose connection will loosen, start to short and burn out, melting the outlet, switch, breaker, dimmer etc, ultimately creating FIRE hazard, especially inside walls. Connect stranded wire to solid copper using wire connector. DO NOT SOLDER stranded to make solid wire. For stranded wire, use crimp-on terminals. Household NM-B Wires (pictured) are color-coded so inspectors/ electricians can easily identify which gauge wire is used during construction or remodeling. If your home was wired by professional electrician who pulled permits, then circuit breaker and wire size and devices will match correct practice, and wires will be solid copper 600 volt. If manufactured home or travel trailer has not been altered by homeowner then the electrical work should be code and correct. Safe maximum 80% breaker rating ''Maximum loading of any circuit breaker is 80% of rating for non-motor loads. Look at label on each load (TV, refrigerator, box fan etc). Add up total watt load on circuit. Divide the watts by the voltage on line = amps. For motor Loads multiply running current by 1.75-2.50 to get circuit breaker size'' If breaker (or fuse) is oversized for wire... then the small wire is not rated for the amps (current of electrons) that are flowing through the breaker (overcurrent protection). Too many amps (electrons) flowing down the wire will heat the wire. Why? Too many electrons are being pushed through the small wire by the voltage. The voltage doesn't change. It stays level 120 or 240 volt, and voltage never stops pushing the electrons. The breaker (overcurrent protection) is not designed to respond to voltage unless it exceeds the breaker's rating parameters (for example a lighting strike or power company transformer failure). In normal household conditions, the voltage only varies slightly with momentary surges when loads activate, and the breaker does not respond. However the breaker is designed to respond to the amperage (current of electrons). If the breaker is too large for the small wire, then too many electrons are getting pushed down the wire. The natural resistance of the small wire causes a friction, which overheats the wire. The oversized breaker does not respond correctly to the heat on the wire, creating absolute FIRE danger. To determine if wire is too small for breaker, buy short lengths of correct size wire, and compare with existing wire. Open a switch box and compare sizes. Call electrician if you suspect wiring is not correct. Code "Type NM-B (Non-metallic sheathed cable) has a broad range of usage as defined in Article 334 of the National Electrical Code (NEC). Type NM-B cable is commonly used for residential wiring of luminaries Lights), devices and appliances. Type NM-B ampacity limitation shall be in accordance with the 60ºC (140°F) conductor temperature rating (higher temperatures increase resistance and lower efficiency), as specified in the NEC. Type NM-B is rated 600-volt for both exposed and concealed work in normally DRY locations. Type NM-B may be installed or fished in air voids and joints and in masonry block or tile walls where such walls are not exposed to, nor subject to, excessive moisture or dampness." Buy: Southwire at Amazon Resource: How to select wire and breaker
Damp- wet locations: For direct burial underfoot, in contact with damp soil ... or for other damp locations ... use UF-B wire ... or use plastic conduit. UF-B wire can be difficult to strip back for wiring. Buy: UF-B wire Southwire
Circuit breaker and wire size must match Chart on left shows that 30 amp breaker matches 10 gauge copper wire. Do not use aluminum wire. Copper wire is safe. If circuit is loaded to safe maximum 80% of ampacity, and distance to load is around 100 feet, then voltage drop will require larger wire size. Larger gauge wires are stranded. These wires must be joined carefully with wire nut, but preferably are run in full lengths only and terminate at a LUG connection that will clamp down hard enough to hold wire in place despite heat when in use. All wire expands when electricity travels through wire. Aluminum wire expands more than copper wire. Expansion causes connection points to come loose resulting in fire hazard. Special compression fittings and CO-AL rated devices must be used with aluminum wire. Image on left shows rating for lengths up to 100' feet for household NM-B (cannot be exposed to wet conditions) and DU-F (direct bury underground) Resources: Larger image with wire types, temperature, long length Maximum wattage for household NM-B and DU-F wires Wire diameter, weight, resistance
'Extension cords: 'Flexible cords and cables may not be used: a. As a substitute for the fixed wiring of the structure; b. Where run through holes in walls, ceilings, or floors; c. Where run through doorways, windows, or similar openings; d. Where attached to building surfaces; or e. Where concealed behind building walls, ceilings, or floors." Flexible cord splices, repair and connections: "Flexible cords (extension cords) shall be used only in continuous lengths without splice or tap. No. 12 or larger, may be repaired if spliced so that the splice retains insulation, outer sheath properties, and usage characteristics. Flexible cords shall be connected to devices and fittings so that strain relief is provided which will prevent pull from being directly transmitted to joints or terminal screws." In other words, the cord must be connected or held in place by a clamp or other means so it cannot be pulled loose from terminal screws. Extension cords are temporary and cannot be concealed inside wall. Extension cords are made for plug ends, and have stranded wire instead of solid wire. Never put stranded wire under screw plate of switch, timer etc. or it creates fire hazard. Safety: Check electrical cords to make sure they are not running across doorways or under carpets. Extension cords are intended for temporary use. Add more receptacle outlets so you don’t have to use extension cords. Buy: 12 gauge extension cord
Electrical safety .pdf Don't minimize the hazard with stranded wire ... I've gotten emails from folks with burnt up timers etc resulting from stranded under a screw terminal, or combining stranded and solid wire under screw plate... Mostly it's not a problem until the Load (light fan motor etc) starts drawing high amps ... Do NOT solder stranded wire to make solid, or depend on solder joint instead of wire nuts, connectors, terminals. Solder will melt with higher amps. What causes heat on electric wires? The way it works: Household voltage pushes a current of electrons (amperage) through the matrix (atomic structure) of a conductor ... voltage stays same throughout, but amperage varies by the watt demand of appliance ... the more amps getting pushed through the wire results in heat caused by natural resistance in all materials ... the heat melts solder, but also causes expansion and contraction of connections,. Then over time stranded comes loose if not crimped to a terminal etc. How tight should wire be connected? Always tighten screws very tight against copper wire ... and compress terminal connects as hard as possible, using only quality terminals. Don't use aluminum wire without proper rated connections, because aluminum expands more than copper and comes loose. So is stranded comparable to using aluminum? I guess stranded copper is better than aluminum, but caution is advised.

Strip wire

To strip cover:
Using utility knife with fresh blade, carefully cut through plastic sheathing.

Cut directly down middle of wire over the ground wire.
Do not cut into wires

To strip wire:
Use a wire stripper and not a knife
Cut carefully so the copper is not scored or cut.
Buy tools:
Wire strippers at Amazon

Connecting Wires

Wire connections/
Inadequate splices and connections cause many fires.
-Always tighten screws and connectors very tight against wire. -Do not re-use old twist-on wire connectors.
-Use clean wires ... sand off any corrosion, cut back any melted or burned end. Do NOT use damaged wire.
-Twist wires together so there are no gaps or looseness, and then cover completely with wire connector.

-Make hook shape with needle nose pliers when attaching wire to screw terminal.
-Never use stranded wire under screw terminal. Instead crimp on a terminal.
Heavy gauge wires are stranded. The wires can be joined inside a box using correct size large wire connector. Large wires should be connected to devices (subpanel etc) using a lug. Very large wires found in service disconnects and main breaker box require hex wrench for correct tightening.
-Straighten wires for lug and terminal connections.

How tight should wire be connected?
Always tighten screws very tight against copper wire ... and compress terminal and lug connections as hard as possible, using only quality terminals.
Don't use aluminum wire without proper rated connections, because aluminum expands more than copper and comes loose.
So is stranded comparable to using aluminum? I guess stranded copper is better than aluminum, but caution is advised.
Resource:
Terminals

Use correct size screwdriver when connecting wire to bonding lugs
Tighten very tight against copper wire.

If using Aluminum wire (not advisable to use aluminum) make sure the safety switch, and lug, or device is rated for CU-AL. Typically, CU-AL rating requires allen wrench to tighten lugs, and not a screw.

Allen wrench will give more torque on the screw so it will tighten firmly and not move.

Larger wire sizes have allen wrench screw for correct torque on the wire

Buy:
Klein screwdrivers
Ground bar
Bonding lugs
Ground or terminal bars
Terminal block

	Copper part of wire is completely covered Twist-on wire connectors are very reliable, and withstand overamperage and severe conditions of residential electricity. Applies to wires that are twisted together Applies to wires that are placed sided-by-side Applies to stranded and solid wires Professional electricians twist size 10-12-14 gauge wires. Larger gauge wires are not twisted together, but joined side by side. Heavy amp wires or large gauge wires are connected side by by side... best is a lug connection. Professional commercial wiring considerations are different than residential wiring in some ways because of higher amperage, more usage, and larger wires etc. Resource How to twist wire
Strip wire carefully so the copper is not scored or cut. Use linesman pliers to twist the wire together. Grab ends of wire firmly with pliers, rotate wrist while holding insulated part of wire. The twist must be tight, with no gaps. Wires must be stripped back to equal length. Ends of both wires must be equal ... use linesman pliers to snip to equal length. Buy tools: Wire strippers at Amazon Linesman pliers Utility knife at Amazon End cutting nippers at Amazon
	How to connect stranded wire and solid wire If stranded wire is thinner than solid: Strip back stranded wire so there is more copper visible than solid wire. Wrap stranded wire around solid copper. Leave solid wire straight. When connecting two solids and one stranded: twist solids together first, then wrap stranded wire around solids. Apply connector very tight. Pull stranded wire to make sure it is tight. If stranded wire is same diameter as solid: Cut off both same length Don't twist together, cover with connector.
Different size and types (solid and stranded) can be joined under same wire connector as shown. If one wire is smaller there is risk it can pull loose, or come loose. or the connector will not bite into the copper and stay fixed to the wires. The main safety question is: Can any of the wires be pulled loose after connector is tightened? Pull on each wire firmly after connector is installed. Check it for sure. A poor connection is a likely source of flickering and failed circuit. A loose connection will begin to arc. IN the best case, it will simply come apart and circuit will fail. Worst case, it can cause fire. If the connection is located inside approved electrical enclosure with matching cover that is secured tightly, the the fire should not spread. Instead the wires will melt, tripping breaker, or simply melt enough to longer make electrical contact, and the circuit no longer works. The smallest wire can be wrapped or twisted together with one of the larger wires. DO NOT SOLDER household wiring Solder is used for low voltage applications (circuit boards) and will melt and come loose when used for ordinary 120-240 volt applications. Use approved wire connector instead. Twist wire connector VERY tight Add black tape to hold the wires together if needed ... this helps hold wires in place both while connector is being installed, and after connection is finished. It is safe to leave black tape holding the wires as illustrated below. Buy Outdoor wire connector Wire connector assortment
Plastic tape and friction tape Use wire connector instead of tape to join wires together. Twist-on wire connector is very reliable under all conditions found in household electrical system. The metal spring coil inside wire nut cuts into and grips wires firmly. Always tighten wire connector very tight. Do not reuse old wire connectors. Tape can be added OVER the top of wire nut ... but it is NOT recommended or necessary. For hard-to-wire connections, wires can be taped together to aid installation of wire connector. Do NOT use tape to cover bare part of wire and then cover tape with wire connector. The metal spring coil inside wire connector must bite into bare copper. Black plastic tape will fail in outdoor application unless sufficient tape is used. Friction tape is better choice than plastic tape for outdoor. With wire connector, the metal coil spring that bites into the copper can deteriorate (rust) in damp locations. Fill wire connector with silicone for more permanent outdoor connection. Professional electricians working with larger wires and higher-voltage commercial applications connect wires using professional grade black plastic tape, sometimes adding friction tape for weather resistance. For these high amperage applications, a lug is best choice. However tape is used for large wires and high amp-volt commercial applications since wire connectors will fail, or connectors are too small for the application. Often the commercial connections consume entire roll of tape per connection. The tape is wrapped very tight and done in specific manner to meet commercial wiring codes.

Keep wires straight
Use solid copper wire
If wiring terminal or end of wire are covered with green, use emery board to clean terminal and sandpaper to clean wire.

Applies to timers, wifi etc/ info source Intermatic Larger image	Both wires MUST be same gauge Straighten each wire If wire is corroded or overheated, clean the end with sandpaper and wipe with cloth. If wire has been melted, cut back and reattach, or replace wire. Tighten screw very tight against copper wire
Use wire connector Use push-on wire connectors	3 wires/ or different gauge wires Join wires with wire connector or push-on connector Run jumper to screw terminal. Buy: Push on wire connectors Red 3P connector (shown) for 10-14 gauge wire Connector assortment Resource: How to select and install wire connector
Larger image	Fire safety/ Do not put stranded wire under screw plate Problem1: picture shows 2 different gauge wires under screw plate Problem2: Stranded wire will expand and contract and come loose under screw plate, even if it is the only wire under the screw plate. Attach stranded wire and solid wire with connector, and run solid copper jumper wire to screw terminal Resources: Timer caught fire Load ratings for Intermatic timers/ pdf

Do not put anything on top of wires.
Plywood, household items, carpet etc pose hazard. Do not set items on top of wire.
Do not step on wires. Any movement or pressure on wires can fray insulation, cause damage, short circuit and fire.
Drill holes through boards, and re-rout wires. Run wires through conduit, and then add spacers so plywood cannot touch.
Code Attic
"Unprotected cable SHALL NOT BE installed within 6 feet of an attic access nor within 7 feet of a permanently installed attic stairway. NEC sec. 336-13"

Wires must be held tight against structure using approved staple, and located away from potential damage or movement.
Staple and hammering the staple cannot cut into or damage wire.
Metal plates must be installed to protect wire from nails

Resource: basic house wiring

Boxes - Enclosures/ for residential and light commercial applications Box fill: Wires should never be crowded into an electrical box
Code "All openings in boxes SHALL BE adequately closed. NEC sec. 370-17a All cable jackets SHALL extend at least 1/4 inch into the box. NEC sec. 370-17c All cable SHALL BE secured to the box, except for single gang non-metallic boxes, if stapled within 8 inches of the box. NEC sec. 370-17c Unused openings in boxes SHALL BE effectively closed. NEC sec. 370-18" “Code requires that individual wires extend into the box at least six inches past the clamping device at least and the sheath to extend at least ¼ inch past clamping device."
Indoor wiring Plastic old-work and nail on boxes, and box extenders are for 120-240 indoor wiring. Not for outdoor wiring where rain, snow etc can come into contact with box. Note the box extension is open on the backside, and cannot be used for 120-240V unless installed over enclosed box. Do not substitute a non-electrical box for enclosing voltage. Electrical boxes have a fire rating, while ordinary household enclosures do not.	Indoor low voltage Structural cable boxes are used for indoor low-voltage communication and media cables. Note that low voltage boxes (up to 12-24 volt AC DC) are open on the backside. Low voltage box cannot be used for 120-240 volt wiring. Ordinary 120-240 volt boxes can be used for low voltage applications. A dual-voltage box can be used for both 120-240V and for low voltage. The enclosed side for 120-240, and open side for low voltage. Voltage divider is required for dual voltage boxes.

Attach enclosure firmly to structure. Attach wires and conduit to enclosure Plastic enclosures do NOT need to be bonded to a ground wire. Code "Bored holes MUST BE 1 1/4 inch from the edges of any stud or top plate. NEC sec. 300-4A-1 2. Notches in studs REQUIRE nail plates. NEC sec 300.4A-2 3. Cable MUST BE stapled at least 1 1/4 inch from the edge of studs. NEC sec. 300-4B-2 4. At least 6 inches of free conductor SHALL BE left at each outlet box for the connection of devices. NEC sec. 300-14"	Attach to structure Wires, cable, enclosures, junction boxes, conduit, subpanels etc must be securely attached to structure. Structure means any permanent anchoring including 2x4, siding, joist, rafter, metal siding, concrete wall, concrete pad etc. Exception could include a temporary meter pole during construction of building. Structure also includes enclosure (box) that is nailed, stapled or screwed into structure, such as a switch box. When applying cable staple, make sure staple does not cut into wire. For metal staples, start by hammering the long side of staple into the wood until the short side begins to enter the wood, then hammer the full staple. Staple should be firm and down tight. Do not over-hammer and damage wire. Connection to structure must be secure and cannot be loose. Applies to metal and plastic boxes, enclosures, wire, conduit, switches etc. Indoor and outdoor. Purpose: so wires, devices and connections cannot be pulled loose and cause electrical short or hazard. Hazardous location: All electrical wiring, boxes, conduit etc must be located away from hazard (forklift, lawn mower etc) that can impact, dislodge, and damage installation. Extension cords cannot be used as replacement for 600 volt electric wire. When possible, raise electrical boxes above anticipate flood and snow events. Do not step into water that could be electrified, such as flooded basement. Do not touch electrical installations that are flooded or have been flooded unless power is off. Hazard: Do not add a vent fan to ventilate heat from any enclosure. All electrical enclosures must be sealed against rapid air penetration that would support a fire. Resources Romex connector Enclosures ''Remove knockout only if conductors are to be run through them. If a knockout is missing or if there is another hole in the box, the hole or opening must be closed.'' Buy: Knockout plugs
Conduit Use plastic boxes and conduit for outdoor installations. Metal conduit and boxes must be grounded, plastic conduit and enclosures do not need grounding, and are best for outdoor installations. -1/2" Conduit is rated for 4 wires of size-12 TH, THW, THWN. Conduit over 50' long, use next diameter larger for ease of pulling. Regular NM-B house wire can be used inside 1/2" conduit. Conduit must fit tightly to the box or enclosure using matching fitting, and be secure so conduit cannot be moved or pulled out. Conduit must be clamped-attached to structure and cannot be loose. Use tapered drill bit to drill KOs into plastic and metal enclosures. Buy Cantex Flexible conduit Carlon Hubbell-Bell Thomas and Betts Arlington enclosures Altelix enclosures Buy tapered drill/ step drill bit for any size hole Drill 3/4" for 1/2" conduit/ drill 1/2" for 3/4" conduit Step drill bits at Amazon Neiko tapered drill bit 1/4"-1-3/8" hole Resource: Enclosures and electric boxes
Do not attach to drywall ... exception: old work boxes that come in wall and ceiling varieties are made to attach directly to drywall. How to install old work box When using plastic boxes, do not substitute boxes that are not rated for electrical heat and spark caused by short circuit Set boxes to match thickness of drywall The old work box installs flush to the drywall surface. Nail-on boxes are marked for thickness of drywall. The purpose of matching the finished surface of drywall is so the cover will maximize protection from spark and potential fire, and not allow space for sparks to get inside wall. Buy Old work boxes
Attach boxes, wires, conduit to structure using nails, screws, staple, clamp etc Structure means solid 2x4, wood siding ... any solid, permanent part of home or building. Staple all wires. Keep wires away from potential nail damage when applying drywall. Set boxes to match thickness of drywall It is important that the box be flush with final surface of wall so the cover fits flat against both box and drywall. Some boxes are marked for thickness of drywall, with marks for 1/2 and 5/8". boxes SHALL BE flush or project from combustible wall or ceiling finishes
Boxes cannot be concealed inside walls. All boxes must be accessible and readily visible for inspection and repairs as needed. If a junction box is absolutely necessary behind a wall, then cut opening in drywall, set box for thickness of drywall, set the box flush with finished wall surface, and then install hardwired or battery-operated smoke detector over top of box. Another possible solution is to use a rectangular wall box, and install blank plate over the box. Buy Smoke detectors

All Metal boxes, enclosures and conduit must be grounded.

Plastic boxes and enclosures do NOT need to be bonded to a ground wire.

Purpose: to protect people and circuits by allowing a resistance free path for electrical short to reach earth.

Code
"Metal boxes SHALL BE grounded with a separate machine threaded ground screw. NEC sec. 370-4 and 250-114a"

Buy
Junction boxes
Electric boxes

Resource:
Enclosures

All enclosures, junction boxes, subpanels, breaker boxes, wall boxes, switches, outlets etc MUST be covered with a cover approved for the electrical box. Do not improvise a cover from material not rated for the voltage and spark of a short circuit.
Resource:
Enclosures, pull boxes etc

Boxes, covers, wires and breakers should not be warm or hot. Exception, some dimmers are hot.
Outlet is warm

Resource:
Troubleshoot warm plugs and wires

Each box, enclosure, panel or connection point requires electrically rated cover.

The cover must be electrically rated to withstand the heat potential of short circuit.

The cover must fit tight onto the box so no spark can exit the box and create fire.
If the box is not flush with wall, the cover will not sit tight against box, leaving space for spark to exit box.
Use a box extension ring so the box will sit flush with finished wall or sit out farther than finished wall.
Box covers must be kept in place and closed.

The cover must be made to fit the box, enclosure or connection.
Using ordinary household box for electrical connections is hazard and not code.
Household boxes made of plastic are a fire hazard. Home-made aluminum, sheet metal and steel enclosure must be sealed equal to electrically box, and all metal enclosures must be grounded.

A light fixture or fan is approved cover. The light or fan etc must sit flat against the ceiling or wall box. Outdoor fixtures must be used for outdoor installations. Using indoor light fixture in an area that gets rain, snow etc is a hazard.
The light must be made to withstand heat of electrical short and heat of the anticipated light bulb. Using a homemade plastic light fixture for 120-240 volt installation is fire hazard.

Hazard: Do not add a vent fan to ventilate heat from any enclosure. All electrical enclosures must be sealed against rapid air penetration that would support a fire.

High heat is the enemy of electrical and electronic installations.
Electrical devices have ambient temperature range for 'weather' related temperatures, ranging -40 to +135° etc. Outdoor wiring and equipment should be installed in sheltered and covered area. Direct sun and high temperatures will degrade electrical, creating failure points, higher power usage, more cost, and added risk of short circuit and electrocution.

Electrical devices, like breakers and enclosures etc have a heat rating based on potential heat caused by short circuit. It is important to install only those devices etc that are rated for electrical heat, and not use extension cord for permanent wiring, or use ordinary household box for connections.

Light fixtures and light bulbs
Light fixtures Use octagon (and round) boxes for ceiling and wall mount lights and fans. Do not use switch box, or non-electrical rated enclosure. Use attachment bracket to secure light to box, then attach box firmly to structure. Round old work box is attached to drywall and is satisfactory for many light fixtures, but not strong enough to support fans, chandeliers etc Code ''Device boxes SHALL NOT BE used for fixture outlets. NEC sec. 370-27'' Buy: Light fixture attachment bracket brace for ceiling fan round old work box	Enclosure for lighting can be metallic or plastic/ do not substitute household box that is not electrically rated Code Recessed "cans" SHALL maintain a clearance from combustible materials. NEC sec. 410-66 Light bulb in closet or attic can cause fire -120 volt attic lights and closet lights should be located away from storage. -Cardboard, paper and other flammables stored near a light bulb is fire hazard. -Solutions: Change to LED bulb, move storage, move electric away, change to battery operated light, install low voltage LED lights High heat light bulbs can discolor fixtures. Fixtures can be spray painted ... BUT ... do not use high heat bulbs afterwards or could be fire hazard. Convert to LED or CFL. Halogen bulbs burn hot just like incandescent. To meet maximum LEED energy conservation: ''All exterior lighting must be Dark Sky qualified and have motion sensor controls, integrative photovoltaic cells, photosensors, or astronomic time-clock operation.'' Exempt emergency and safety lighting
Watt rating and light fixtures Do not exceed watt rating of light fixture. Typical indoor light fixture usually has maximum 60 watt rating per bulb. Can light might be 75 or 150., and then have a thermal reset to reduce overheating. Outdoor aluminum lampholder is 150. Ceramic lampholder might be 60 watt. Watt rating is confusing when CFL, LED etc shows equivalent wattage. Not actual wattage. The watt rating on light fixtures was established for heat produced by incandescent bulbs, but it still applies to newer style bulbs ... so refer to actual watt rating of bulb. Resources Amp rating porcelain lampholders Amp rating lampholders Amp rating incandescent la mpholders

Ground
“Equipment Grounding Conductor” or "Safety Ground" or "Bonding wire"

''For electrical system to function safely and properly, a high quality earth ground is needed. Metal rods embedded in a building’s concrete foundation would be the first choice for an effective electrical ground, followed by well casings or buried metallic water pipes. If not available, a ground rod is used. Often, a ground rod is used to supplement other methods of grounding.
Typical ground rod is a copper-plated steel rod 5/8" in diameter x 8-10 feet in length, driven fully into the ground near service entrance panel.''

Ground. Code NEC (national Electric Code) defines ground: 'A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth or to some conducting body that serves in place of the earth.'

For safety, and to protect circuit breaker and integrity of wires and electric service, each device (switch, outlet, timer, dimmer etc) and each load (microwave, motor, HVAC, pump etc) on a circuit must be grounded.
Exception: double insulated appliances and tools. Do not cut off ground plug.

Each circuit inside home must have a continuous and securely-attached ground wire that is connected to the ground busbar inside main breaker box. The ground busbar must be bonded (connected) to the ground rod. Why you need a ground wire

All device, boxes, conduit, etc must be grounded
Outlet polarity

''The path to ground from circuits, equipment, and enclosures shall be permanent and continuous.
Be of sufficient size and capacity to conduct any fault current likely to be imposed on it. (Fault currents may be many times normal currents, and such high currents may melt or burn metal at points of poor conductivity. These high temperatures may be a hazard in themselves, and they may destroy the continuity of the ground-fault path.).
Ground connection should have sufficiently low impedance (resistance) to limit the voltage to ground and to facilitate the operation of the circuit breakers and fuses in the circuit."

Metal boxes and conduit must be grounded. Plastic boxes and conduit do not need grounding.
All switches, plugs, outlets, motors etc are to be grounded.
Use appliances with grounded plug. Double insulated appliances are ok inside a home.
Outdoor equipment should have 3-prong plug to ensure quick response to GFCI.
Resources:
Why you need ground wire
Basic house wiring

Outdoor motors, pumps, equipment, metal boxes etc must be connected to main panel ground wire, and can be bonded to a separate ground rod as back up.
Local codes vary.
Do not touch metal electrical equipment if power is ON.
Use ohmmeter to verify resistance between earth and motor frame is less than 0.5 Ω

Resource
Why you need ground wire

Circuit or system grounding ... when ground wire is connected to earth at the ground rod.
The main breaker box must be bonded to the ground rod as illustrated.
System grounding is grid-wide, including ground connection at the household service or breaker box, plus on the grid where each pole and electrical installation has a ground connection that is bonded to the Neutral wire that stretches from power station to end user, creating a vast array of ground connections that stabilize the grid against overvoltage, lightning strikes and equipment failure.

Inspect the ground connection at ground rod

If the ground wire is disconnected from ground rod, DO NOT reconnect the ground unless main breaker is de-energized.
Do not touch or remove ground rod. The bare copper or green-insulated wires do not normally carry current. However, they do carry current when they are directing abnormal electrical flow (from short circuit or lightning strike) into earth to help prevent injury and damage

Bond all household all grounds together to maximize protection against surge.
Applies to cable TV and telephone ground etc.
Bonding all grounds together creates an array of grounding at the home or building that helps absorb surge caused by lightning strike.

Never use ground wire for neutral
While the Neutral busbar and ground busbar are bonded (connected) in the main breaker box, each performs a different function.
The ground must provide a direct, uninterrupted connection to ground rod. Using the ground wire as Neutral creates possibility that a short circuit will surge into the device that is connected improperly, creating potential fire hazard.

For basic house wiring diagrams:

Resource:
Basic house wiring

For wiring techniques
When installing house wiring, keep all wires away from potential nail damage.
Secure all wires with cable staples.
Do not cut into wire or cable

Code
Cable SHALL BE secured within 12 inches of each outlet box and every 4 1/2 feet thereafter, and within 8 inches of a single gang non-metallic box without clamps. NEC sec. 336-15

-Bored holes MUST BE 1 1/4 inch from the edges of any stud or top plate. NEC sec. 300- 4A-1
-Notches in studs REQUIRE nail plates. NEC sec 300.4A-2
-Cable MUST BE stapled at least 1 1/4 inch from the edge of studs. NEC sec. 300-4B-2
-At least 6 inches of free conductor SHALL BE left at each outlet box for the connection of devices. NEC sec. 300-14
-Cable SHALL BE secured without damage to the outer covering. NEC sec. 336-15
-Bends in cable SHALL NOT BE less than 5 times (5x) the diameter of the cable. NEC sec. 336-14

Resource:
More illustrations
Installation guideline

Other wiring resources
Surge Protection is a consumable product that absorbs or redirects voltage spikes, and protects circuits and devices from damage. Does not protect from line noise. Use filter for line noise. Multiple surge protection can be used on any circuit. Type 1 is installed anywhere on a circuit, Type 2 is connected to a breaker, Type 3 can be a surge protection outlet, or surge strip etc and jumps the gap to ground wire. Resources: How to wire surge protection	Subpanels are used to expand electric service by adding more breaker spaces. Adding a subpanel does not increase the main breaker rating or increase total amperage available from the service. Subpanel can be added anywhere. Multiple breakers and fuses are okay on any circuit as long as wire and breaker size match. Resources: How to wire subpanel	240 volt outlets are used for window air conditioner, RV hook-ups, electric car, dryer, range welder etc There are numerous styles and types of 240 plugs, outlets, connectors and sockets. Resources: How to wire 240 volt outlets How to wire twist lock devices
GFCI breakers and outlets trips faster than ordinary circuit breaker to protect from shock caused by short circuit. AFCI does the same plus trips when a spark is detected. Install GFCI in bathrooms, unfinished basement, garage, kitchen, laundry room, and on all outdoor plugs. Do not install multiple GFCI on a circuit. Resources: How to wire GFCI and AFCI	Under counter water heaters are used to provide hot water to smaller consumption areas or to supplement or replace main water heater. Resources: How to wire under counter water heater	Electric Tankless water heaters are used as main water heater, or as supplement to supply one area. Tankless electric generally consume more power per gallon of water heated than any other style heater. Resources: How to wire Tankless water heater
Terminology for wiring Load = light bulb, motor, fan, heater, pump etc; Total load = add up wattage on all Loads. Resistive Load: incandescent light bulb, heating element have uniform voltage and amp draw; Inductive load: motor, pump etc. Inductive loads pull more amps during start up. Load rating... light bulb shows wattage, label on water heater shows volts-watts, timer labels show rating for inductive or resistive etc Figure volts amps watts Volts x amps = watts Water heater formulas .pdf Hot wire = wire or wires that carry voltage potential and would shock you if breaker was on Image residential breaker box Neutral wire = Grounded Conductor = A system or circuit conductor that is intentionally grounded. By code, a white wire used for 120V and 277V circuits to complete circuit along with a Hot wire. Ground = NEC (national electric code) defines ground: A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth or to some conducting body that serves in place of the earth. Grounded = Effectively. Intentionally connected to earth through a ground connection or connections of sufficiently low impedance (resistance) and having sufficient current-carrying capacity to prevent the buildup of voltages that may result in undue hazards to connected equipment or to persons. Ground wire = green or bare copper wire that connects to ground busbar in breaker box Why ground is needed Grounding electrode = earthing electrode (ground rod) Ground resistance = resistance due to the resistivity of the soil in the vicinity of the grounding electrode 208 and 240 volt single-phase circuits have 2 Hot wires. (US electric) Image residential breaker box Some countries have 230-240Volt circuits with 1 Hot and 1 Neutral (instead of 2 Hot wires). What is 208 volt 120 and 277 volt circuits have 1 Hot and 1 Neutral / Usually 277volt is found in commercial applications (US) What is 277 volt Standard voltages in US and Americas include 12V 24V 120V 208V 240V 277V 480V 600V etc found in various applications Voltages around the world vary depending on country. Standard voltages make it possible to mass produce wires, breakers, appliances etc. 60Hz or 60 cycle = number of times AC generator rotates each second. Americas use 60 Hz power, while other countries use 50Hz. Read more DC direct current is generated by solar panels and batteries. Large arc when switching high voltage DC is fire hazard. Device must show DC rating. Read about DC vrs AC AC alternating current produced by power plant, windmill, or portable generator. More Single-phase = residential electrical systems are single phase AC, requiring 2 wires to complete circuit More Three-phase = commercial wiring requiring 3 Hot wires to complete circuit More Wire gauge = diameter of wire. The wire size and load rating and breaker must match Select wire and breaker Breaker: circuit breaker is overcurrent protection that will trip when amp draw from Load or short circuit overheats wire. Turn breaker fully off and then fully on. Jumper = short wire used to connect 2 electrical points together. Fuse: A piece of metal, connected in the circuit, that melts and interrupts the circuit when excess current flows. Transformer = converts voltage and amperage ratio on a line. Cell phone charger, doorbell transformer, LED driver are examples of changing 120 volt into safe, low voltage applications. On the grid, transformers are used to supply 120-240 to household, and other voltage combinations to local business and industry. Insulation = Common usage: electric wires are coated with insulation to isolate each wire from coming into contact with other wires. Removing the insulation is necessary when connecting wires. Professional usage: The action of isolating sources of electricity from coming into contact with other wires, boxes, earth, people, appliances, etc is referred to as insulation. A fault, where electricity has reached earth unexpectedly or breeched a layer of containment, is known as an insulation failure. In motors: motor insulation is classified by maximum allowable operating temperature. Power Factor: measure of the effectiveness with which a device converts volt-amperes to watts

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