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Troubleshoot household electricity: general reference for homeowner & electrician
Resources:
Safe electric wiring
How to troubleshoot loose wire, ground fault, or short
How to wire devices, and how electric devices work/pdf
E-mail: geno03245w@gmail.com
wire nut safety Never assume electricity is OFF
Power safety:
Turn power off
Never stand in water or wet surface when around electricity
Never stand on bare soil
Stand on dry boards
Electricians use fiberglass ladder
Do not touch or lean into anything made of metal
Use non-contact voltage tester to make sure power is OFF before making repairs
Use GFCI-protected circuits for bathroom and outdoor circuits.
 
Use non-contact voltage tester on timer, on wire, on outlet to see if power is present.
Press button on tester, if single beep then no power is present. If continuous beep then power is present.
Tape tester leads to wood sticks, never touch wet water heater, or flooded water heater, or timer that had a short or fire without turning power OFF.

Buy:
Multimeters at Amazon
Buy non-contact voltage tester at Amazon
Electric testers at Amazon
Resources:
How to wire GFCI
Wire connectors
main breaker boxLarger image
Residential Main panel
Single-phase electric service has 120 and 240 volt circuits. T wires are required to complete each circuit

240 volt circuits consists of 2 Hot wires and a ground wire that supply power to one device, such as pump, clothes dryer, air conditioner. The electric dryer is connected to one 240 volt breaker. The AC is connected to another 240 volt circuit breaker, etc.

120 volt circuits have 1 Hot, 1 Neutral and a ground wire that supply power to lights, fan, outlets etc. with maximum 12 boxes per circuit.
Some 120 volt circuits are dedicated, and supply power to one device such as microwave because the appliance consumes the full amp load the breaker can supply. Some power vent water heaters and other electronic devices are on a dedicated breaker to reduce electrical interference.

- Generally a 120 volt circuit supplies power to one area of home. The wire leaves breaker box and go to first junction box, which is typically a ceiling box. From the junction box, the wire splits off and goes to each individual box, traveling from box to box to a maximum number of 12 boxes until the final box is reached. Each box will have 1 black hot wire, 1 white neutral wire, and 1 ground wire that connect back to main breaker box.
Resources:
See inside main breaker box
How to replace circuit breaker
How to install subpanel
Figure volts amps watts for electric water heater
Basic house wiring
How to reset circuit breaker How to reset circuit breaker
Circuit breaker can look ok, but still be tripped.
Push circuit breaker fully OFF, and then fully back ON.
Circuit breaker amp rating
Each circuit breaker is marked with amp rating. Amps cause heat. When heat on the wire exceeds amp rating of breaker, the breaker trips off power to the circuit.
Match wire size and breaker amp ratingwire size chart
If you suspect wiring is not correct, call electrician. If your home was wired by professional electrician who pulled permits, then circuit breaker and wire size will match. If manufactured home or travel trailer has not been altered by homeowner then breaker and wire size will match.

Circuit breaker and wire size
Example: Use 10 gauge wire with 30 amp breaker. This applies to either 120 or 240 volt: Each appliance and device has a rating plate that identifies volts and watts, or volts and horsepower. Any 120 volt electrical device rated 20 amps requires 20 amp breaker and 12 gauge wire. Any 240 volt electrical device rated 20 amps also requires 20 amp breaker and 12 gauge wire. 

If wire is too small or breaker is rated too many amps for the wire, then breaker can let too much electricity travel through the wire. Wire can overheat and cause fire. Always match wire and breaker size. Household NM-B Wires are color-coded so inspectors/ electricians can easily identify which wire is used during construction
Resource:
  Match breaker and wire size
Copper wire vs aluminum
Do not use aluminum wire. Copper wire is safe. Aluminum wire expands when electricity travels through wire. Expansion causes loose connections and fire hazard. Special compression fittings and wiring devices are required for aluminum wire installations. Best to avoid aluminum altogether.
Longer length wires and motors/ pool pumps/ shop tools/ 120-240 volt
Longer runs of wire must be larger to handle same amp load.
This is especially important when troubleshooting a shop inside a detached structure, or installing a water pump located several hundred feet away.
Resources:
Match breaker and wire size for distance
Motor wire size and distance
Figure volts amps watts

Each electrical device has a rating plate with amps and watts
14 amp device is ok on 20-30 amp line
20 amp device is ok on 30 amp line
20 amp device is not ok on 15 amp line
30 amp device is not ok on 20 amp line
Resources:
How to wire switches
How to add a switch
Replace outlet with combo switch
How to add outlet
How to wire Combo switches

Ground outdoor motors and boxes
Never use ground for Neutral
Never use Neutral for ground
Using ground as a Neutral can cause the short circuit and potential fire to detour into the device that is improperly connected.
Bond all grounds together to help protect against surge and lightning damage.
Use ohmmeter to verify resistance between earth and motor frame is less than 0.5 Ω
Resources:
Why you need ground wire
Difference ground vs surge
   
GFCI breakers and outlets trip faster than ordinary circuit breaker to protect from shock caused by short to ground. AFCI does the same plus trips when spark is detected.
Install GFCI in bathrooms, kitchen, laundry room, and on all outdoor plugs.
Resources:
How to wire GFCI and AFCI
What causes electrocution

Not enough space for circuit breakers
How to add tandem breaker
How to install subpanel
How to replace circuit breaker

Buy:
124TP2608A 4 breaker spaces
124T2530A 8 breaker spaces

Under counter water heaters are used to provide hot water to smaller consumption areas or to supplement or replace main water heater.
When adding appliances, check the rating plate for volts and amps. Always match wire and breaker size.
Resource:
How to wire under counter water heater

Electric Tankless water heaters are used as main water heater, or as supplement to supply one area.
Wiring is straightforward if the circuit breaker panel has enough spaces and capacity for the amp draw.
Resource:
How to wire Tankless water heater

Every electrical device and connection needs to be contained within an enclosure with cover.
Secure wires and conduit to structure using staples, clamps etc. so the wire cannot come loose.

Wire ends should be twisted together and covered with wire connector.
Resources:
Enclosures
Romex connectors
How to twist wire
Wire connectors/
Lever switchWeatherproof lever switch on outdoor lights
Safely operate outdoor toggle switch
Replaces outdoor cover
Install over top of ordinary switch
Works with single-pole, double-pole, 3PST, 3-way, 4-way switches etc
Use weatherproof box for outdoor
Can be used indoor or outdoor

Buy:
Best choice: Cantex lever switch
Outdoor lever switches at Amazon
Lever switches

Resource
Cantex-toggle-switch-covers.pdf
Cantex-PVC-junction-boxes.pdf

Safety switch
Resource:
How to wire safety switches
surge protector
Surge Protection is a consumable product that absorbs irregular voltage and protects circuits from damage.
Resource:
How to wire surge protection

Subpanels are used to expand electric service by adding more breaker spaces
Resource:
How to wire subpanel

240 volt outlets are used for window air conditioner, RV hook-ups, electric car, dryer, range welder etc
Resources:
How to wire 240 volt outlets
How to wire twist lock devices

Solid copper Nm-B / UF / DUF  double sheathed cable is code.
Do not use extension cord for house wiring.
Color code for house wiring
Do not solder connections in house wiring.
Do not use stranded wire for permanent wiring.

Extension cords must be used with plug, connector and socket.
±
Safety test for household electrical system
Easiest way to see if there are electrical problems is the heat test
All appliances, computers, TVs, AC etc put off heat. But breakers, extension cords, wires, outlets, switches and timers should not be warm.
electrical safety All electrical boxes, including outlets and switches must have cover plate
Stop sparks and overheating from causing fire
Outlet is warm
• Frequent problems with blowing fuses or tripping circuit breakers
• A tingling feeling when you touch an electrical appliance
• Discolored or warm wall outlets
• A burning or rubbery smell coming from an appliance
• Flickering or dimming lights
• Sparks from an outlet
Resource:
Safe electric wiring
Outlet/ Switch is warm or hot
Use hand to check if outlets and switches are warm.
If switches and/or outlets are warm, then call electrician.
Turn off power. Remove cover and inspect for loose wires. Replace switch or outlet. Monitor if new switch/outlet gets warm. Check that wire is copper and not aluminum. Add up total watts  being handled by circuit and divide by 120 volts to check amp load. Each light bulb, appliance, electronic gadget has amp rating located on the device.

Aluminum wiring is absolute fire hazard
If wires are aluminum, then this is absolute fire hazard. Professional electrician must be called to solve problem.
Aluminum wire must be replaced with copper. Special outlets-switches required for aluminum wire. Special connections required for aluminum wire.
Resource:
How to wire switches
Safe electric wiring
circuit breakers are warmCircuit breakers should not be warm or Hot
Check if breakers are warm
It is absolutely safe to open the main breaker access door and touch circuit breakers as illustrated on left. When finished keep the panel door closed.

DO NOT unscrew and remove the cover off main panel without knowledge of safety and electric wiring experience. Even if the main breaker is turned OFF, the wires entering the main breaker are HOT. Main breaker terminals are still Hot when main breaker is turned off.

Put hand on each circuit breaker. Including main breaker. There is no shock hazard touching circuit breakers when box cover is in place.

Always stand on totally dry surface when touching anything electrical. For example stand on dry boards.
Breakers should not be warm.
Warm circuit breaker indicates problem.

What does warm circuit breaker mean? It means breaker is Overheating
1) Breaker is going bad. Wiggle the breaker back and forth, and use nose and ears to listen for crackling sound and burning.
2) Breaker is not big enough to handle Load, so amp draw is larger than breaker.
3) Breaker has been getting warm over time and is loose on the busbar.
4) There are loose wires somewhere in the circuit that are causing arcs and heating
Resource2:
Read main breaker stress test
How to replace circuit breaker
Water heater is tripping breaker
How to find ground fault

replace circuit breakerCircuit breaker is tripping
Use wire size and maximum load calculations above to see if
breaker is over-amped.
Move load to different same-size breaker.
If same breaker continues tripping, then replace breaker.
If different breaker trips on same load, then look for shorted wire.

Circuit breaker is warm
Use wire size and maximum load calculations above to see if breaker is over-amped.
Move load to different same-size breaker.
If same breaker continues getting warm, then replace breaker.
If different breaker gets warm on same load, then look for over-mapped circuit.
Resources:
How to replace circuit breaker
Water heater is blowing breaker
How to find ground fault
Heat means energy loss and possible hazard
Vacuum cleaner cord gets hot''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 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.

Cords should not be warm if they are used full-time

If you are using extension cord as full time source of electricity for pump or fan, the cord should not be warm or hot
If toaster oven cord gets warm when used, then that is normal
If you operate the appliance full time, then upgrade to larger cord or professional appliance
Buy
12 gauge extension cord


damaged extension cordVacuum cleaner cord gets hot/ Extension cord gets hot is hazard
Put hand on extension cords, and household wires. Feel for warmth.
If cord or wire is warm, then that indicates appliance or tool is exceeding safe-maximum. It shows the cord is too small for amp-rating of tool. Or the wire is undersized for load.
A clothes dryer, window air conditioner, and microwave cords should NEVER be hot.
Use larger size extension cord. For example, upgrade from 14 gauge to 12 gauge or upgrade to 10 gauge.
Cords frequently get warm, and that is not good. Warm indicates high load, and wasted electricity.
Warm is not good, but Hot is dangerous. Cords and wires should never get HOT.

If cord is hot, unplug immediately.
Vacuum cleaner cords frequently get hot, because manufacturers are under-sizing the cord for the amp-draw of the appliance motor. This is typical for cheaply made consumer appliances today like toasters, blender, vacuum cleaner etc.
Over time, the warm cord means motor is starving for electricity. Motor runs under-speed, causing motor to get warm, and weaken over time. Motor finally gets hot and begins to short. Cord get hot. Vacuum cleaner needs to be replaced.

Space heater cords frequently get warm
This means the cord is too small for amp-draw of space heater.
Space heaters should never be operated for long hours, and should always be unplugged when not in use
1500 watt space heaters usually come with 14 gauge wire, but 80% safe-maximum rule says 14 gauge wire is rated for 1440 watts.
14 gauge wire is moderately  OK for space heater, but load is above safe-maximum so wire can feel warm, wasting energy.

Manufacturers make more money selling cheap products, while corporate owners complain about government codes and regulation. Then your house has hazards, your electric bill is higher ... or your house burns down and insurance company says to sue appliance manufacturer.
Unplug appliances that are not being used

Buy 12 gauge heavy-duty extension cords:
12 gauge 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 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.
1000 watt dimmerDimmers are usually warm when ON/ but Never Hot
Dimmer is getting hot


Change light bulbs to lower wattage or LED. Replace dimmer with new dimmer.
Turn off power. Pull dimmer out and look at watt rating printed on side of dimmer.
Add up total watts of all light bubs controlled by dimmer. Compare dimmer rating with actual watt rating.
For example if dimmer is rated for 600 watts, then four 150 watt light bulbs will cause dimmer to get warm. B
uy dimmer rated for 1000 watts.
Dimmer getting hot
Cover plate must be installed for safety
Typical 600 watt rotary dimmer
Some dimmers have aluminum fins that work as heat sinks.
Aluminum dissipates heat very fast. The aluminum fins can be warm, and that is normal.
Aluminum fins should not be hot.
Buy from my affiliate links:
Dimmers at Amazon


transformerTransformer/ power supply/ are usually warm
Every home has transformers. Used for cell phone recharging, computer, alarm system, door bell, low voltage light systems, inside every appliance etc.
Transformers have no moving parts, long life and relatively high efficiency.
Transformers can make humming sound
Transformers are usually warm, but should not be hot to touch. Heat means energy loss and inefficiency.

Buy:
Power supply to convert 120 to 240 etc
Doorbell Transformer
24 volt Transformer for security systems etc

Resource:
Troubleshoot Malibu power pack
How to identify doorbell wires
Intermatic EI500   Westek TE06WHB   Intermatic EJ351 Timers should NOT be hot to touch
Timer is getting hot

Inspect wires. Frayed or loose wiring can cause overheating inside box.
Replace timer.
Use product manual or information
printed on side or back of timer to check load rating.
Compare timer rating with the watt and amp rating of Load.
For example, if timer is rated for 500 watts incandescent light bulbs, but timer is connected to 600 watt TV or 1 Hp pool pump, then timer will get warm or hot, and burn out.
Resource:
How to wire timers
How to troubleshoot timers
 Flickering lights
Table lamp flickering:
Table lamp can have loose bulb, bulb that is going bad, loose wire, bad lamp holder, bad plug, frayed cord, loose wire in outlet, loose wire in the circuit, loose wire on breaker, bad breaker.
Check bulb and lamp wire first. Try lamp in another outlet in different room,
plug another lamp into same outlet, check other lights and plugs on same circuit breaker. Replace outlet, continue troubleshoot steps.
Ceiling lights flickering
Ceiling lights can have loose bulb, bulb that is going bad, loose wire in ceiling box, bad lamp holder, loose wire in the circuit (usually the Neutral located under wire nut), loose wire on breaker, bad breaker.
If all lights and outlets on circuit are flickering, then problem is typically in the breaker box. If all lights in one room are affected, find the junction box that is common to all devices (usually in the ceiling), and check for loose Neutral wire(s) tied together with wire connector.
Tighten loose wire on circuit breaker before sparking causes damage in breaker box. Check breaker and listen for fizzing or crackling sound. Check if the breaker screw is tight against wire. Other suspects include loose quick connection on back of outlet or switch Start by opening each box and jiggling the outlet or switch.
Always put cover back on outlets, switches etc to prevent sparks from leaving box.
Outdoor lights flickering
Outdoor lights can have loose bulb, bulb that is going bad, loose wire, corroded connection points, bad lamp holder, loose wire in the circuit (usually the Neutral located under wire nut), bad switch or timer, loose wire on breaker, bad breaker. Be careful when working on outdoor lights. Hardwired lights may not be on a GFCI outlet. Lights plugged into outlet should on GFCI. How to wire GFCI

Fire inside timer caused by stranded wire
Keep enclosure door closed at all times
Sparking wires
Sparks from a loose connection usually will not damage other wires, unless the short circuit has been going on for a while... but usually a short circuit will trip breaker or the arcing will completely short out and no more electricity will flow.
Always use NEW wire connectors
Use silicone to seal outdoor wire connectors
Do not use undersized wire
Do not use stranded wire under screw places on timers, switches, outlets etc
Make sure everything is properly grounded
Overheated wire can catch wire and melt other wires.

Resources:
Match wire and breaker size
How to install wire connector
Grounding
Melted wire
Replace wire
Test circuit
Look for other affected wires and bad circuits
Check wire and breaker size
Rodents and other pests can gnaw through wire

Resources
How to test wires
Grounding
Burned thermostat Burned switch / burned electrical part
Turn power off
Check condition of wires
Cut back damaged wire
Test wires with multimeter
Check that device has same electrical rating as wire and breaker
Replace part
Make sure everything is properly grounded

Resources:
Match wire and breaker size
Grounding
Intermatic terminal wires Intermatic DTMV2 defrost timer
Keep timer door closed
Prevent fire inside timer and electrical boxes
Use only copper wire/ never aluminum wire
Tighten screws very tight against copper wire.
Match timer rating with Load rating
Never mix stranded and solid copper wire under same screw plate.
Never mix 2 different gauge wires under same screw plate.
Make sure only copper is under screw plate, and that no insulation is under screw plate.
Always keep timer door closed
Connecting wires with screws
Examples: Outlet, switch, circuit breaker, timer, water heater thermostats.
Wire connections
-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.

-Straighten wires for lug connection

-Twist wires and cover completely with wire connector. The twist must be tight and not loose.

Always tighten screws and connectors very tight against wire.
Intermatic IG1240RC3 Whole house surge protector/ protect appliances, wiring, timers, water heaters etc
Appliances, water heaters, timers, circuit breakers are not protected from surge
Most appliances today have electronics. Few of these appliances are protected from surge
Water heaters the plug into outlet are not protected from surge
Homeowner insurance might have appliance exclusion. Read policy
Water heater warranty does not cover surge event.
Protect 120V and 240V circuits with whole house surge protector
Resources
How to wire whole house surge protector
Intermatic IG1240RC3 whole house surge protector/ pdf
Main breaker stress test
Using 80% rule: Safe maximum for 125 Amp main breaker is 100 Amps
Safe maximum for 60 Amp main breaker is 48 amps
Main breaker is getting warm
Main breaker is tripping

Information: Why the main breaker stress test is useful.
-Voltage is the amount of power pushing electrons on the wires. Voltage only changes  slightly if at all, depending on power line voltage and not on how much power being used.
-Amps are the flow of electrons on the wire. Number of amps is constantly changing with amount of power used.
-The more electrons flowing, the harder they have to push against the matrix of the copper or aluminum conductor ... since the conductor is limited in size, when amps exceed wire capacity, it causes higher resistance, producing heat.
-A loose connection point can also cause heat. For example loose wire or damaged breaker bus.
-The breaker responds to heat ... when heat exceeds breaker rating, the breaker trips.
-If the main breaker has a wire that is not completely tightened down, the main breaker will trip.
-If the breaker gets hot for long enough it can weaken the connection points to the busbar ... they get loose, and the main breaker box gets ruined.
-If the stress test shows too many amps are being used, then reduce consumption, stagger usage, or upgrade service to higher amp rating.  This requires a larger capacity breaker box, and possibly larger incoming wires from the power company transformer.
Calculate PEAK amp draw.
Add up PEAK amp usage using example below.
Formula: Volts x amps = watts. or Watts divided by volts = amps.
If appliances are gas, then they do not count.
Look at labels on each item for watt rating.

Add up peak usage for 120Volt. Each electric appliance has rating label.  For example: microwave 1500 watts + big screen TV 500 watts + computer 300 watts + refrigerator 700 watts + lights 240 watts + dishwasher 800 watts + 1 Hp hot tub pump 750 watts + washing machine 350 watts etc = 5320 watts divided by 120 volts = 44 amps.
Add up peak usage of 240Volt. For example water heater 4500 watts + heat/ac 5000 watts + clothes dryer 1800 watts + 1 Hp water well pump 750 watts + top and bottom ovens 7500 watts etc = 19550 divided by 240 volts = 81 amps.

Total PEAK amp draw = 81 + 44 = 125 amps.
Home may only reach PEAK once per week or once per month. Try to estimate actual peak usage that would be likely to occur.
125 amp Main breaker
Main breaker
PEAK amp draw is STRESS test for main breaker
Example calculation above shows peak 125 amps.
If main breaker is 125 amps, then main breaker is too small to handle 125 amp PEAK load.
Each time PEAK amps are used, the main breaker gets warm.
Sooner or later, the main breaker has gotten warm too many times, and it stops functioning. This may take years before main stops functioning.

Electricians use 80% safe maximum rule when calculating capacity of electrical devices such as circuit breaker.
80% rule also applies to switches, outlets, dimmers, timers, etc.
If main breaker is rated 125 amps, then electricians multiply 125 x 80% to find maximum safe load for that breaker.

125 amps x .8 safe maximum = 100 amps
So safe maximum for 125Amp main breaker is 100 Amps.
If PEAK usage exceeds safe maximum for breaker, then breaker is getting warm, and is more likely to get hot and fail.
Main breaker is getting warm/ Hot If Main breaker is getting Hot
If stress test shows that main breaker is within safe maximum, then replace main breaker.
If stress test shows main is above safe maximum, then upgrade service panel to higher amp load center
Resource:

How to replace circuit breaker
Circuit breaker is getting warm/ Hot If circuit breaker is getting warm or Hot
Move wire to another same-size breaker. Check if same-size breaker is also getting warm or hot.
If same size also gets warm, then circuit is over amped. Call electrician. Identify all items using that breaker. Move appliances to different circuit.
If same size does not get warm, then replace circuit breaker that is getting warm.
Resource:
How to replace circuit breaker
water heater circuit breaker

4500 watt and 5500 watt water heaters should connect to 30 amp breaker and 10 gauge wire.
Calculate safe maximum for water heater circuit
If residential water heater is connected to 20 amp breaker and 12 gauge wire, then the same overheating problem occurs over time.
Circuit breaker will not last as long, and damage can occur to busbar.
Resource:

See basic water heater circuit
20 amp breaker is subject to 80% safe-maximum rule.
20 amp circuit breaker x .8 = 16 amps. So safe maximum for 20 amp breaker is 16 amps.
240Volt 4500 watt water heater draws 18.75 amps. And 5500 watt water heater draws 22.91 amps.
So 20 amp breaker with 12 gauge wire is rated too small for most water heaters. Over time the breaker is getting warm, and is more likely to get hot and fail.

Recommended that all water heaters be connected to 30 amp breaker and 10 gauge wire.
Safe maximum for 30 amp breaker x .8 = 24 amps.
Safe maximum for 10 gauge wire at 240volts is 5670 watts See chart
30 amp breaker and 10 gauge wire run cooler, with less heat loss and more efficiency. Circuit breaker and main box last longer with less chance for heat damage.
Resource
Figure Volts Amps Watts for water heater
Calculate safe maximum for water heater circuit
Read label on side of water heater for element wattage. Element wattage is tank wattage.
For example: If water heater has 5500 watt elements: 5500 watts divided by 240Volts = 22.91 amps
4500 watt water heater divided by 240Volts = 18.75 amps.
Electricians use 80% rule for safe maximum. WH21 is rated for 25 amps x .8 = 20 amps.
Calculation shows that WH21 is ok for 4500 watt water heater, but beyond safe-maximum for 5500 watt water heater.
Exceeding safe maximum means WH21 will run hot and not last as long.
Volts x Amps = Watts
Watts divided by Volts = Amps
Most residential water heaters are non-simultaneous. This means both elements are not ON at same time.
Resources:
Figure volts amps watts for water heater
How electric water heater works
How to wire thermostats

If electrical device is run at-or-near maximum amp rating, the device will not last as long because of heat.
Same as running a car at full throttle. Car will not last as long.
In contrast, 40-amp WH40 and T104 timers are better long term investment for water heater timer.
WH40 and T104 are rated for 40 amps, with safe maximum of 32 amps, so they withstand more amperage without heat loss, and will last longer.
Resources:
How to wire WH40
How to wire T104
Intermatic T174 timer is identical to T104, except T174 has day-skipper feature

- Some gas water heaters plug into 120Volt outlet that should also be on a dedicated breaker. This is to prevent electrical interference from affecting gas control valve. This type of installation should also include surge protector to prevent surge from knocking out gas control valve electronics.
in line fuseUse in-line fuse when connecting 2 different gauge wires
Illustration shows smaller 12-2 cable connected to larger 10-3 cable.

The 10 gauge wire carries 240 volt plus a Neutral wire, and is protected by 30 amp breaker
The amp draw on 30 amp breaker is too large for 12 gauge wire.
12 gauge wire should have 20 amp breaker.
Connect smaller 12 gauge wire to 10 gauge wire using twist on wire connector. All connections must be inside electrically rated enclosed box with cover.
Use fuseholder with 20 amp fuse.
Fuse will protect entire length of 12 gauge wire.
Connect fuse to Hot wire.
Never put fuse on Neutral ... the Neutral wire must never be switched off, and must run continuous throughout installation.

If the 12 gauge wire is wired for 240V, instead of 120V shown in illustration, then fuses can be added to both hot wires.
Always make connections inside a box with cover
Buy:
Panel mount fuse holders at Amazon
ANL fuseholder
Buy fuseholders
Din rail fuseholder
10 x 38 mm fuse
Electrical terminals
Solder guns
Resource:
See fuseholder
Terminals
Some fuseholders accept terminal connections, some have solder-only connections. Fuse block has screw terminals.
Busman HKP-HH fuse holder
surface mount fuseholder

Yellow female terminal for 10-12 gauge wire
Blue female terminal for 14-16 gauge
 Available hardware store, home center, electric supply, lighting store, internet
Buy:
Terminal kit at Amazon with crimp tool
Electrical terminals at Amazon
Blue 14-16 gauge female terminals 20 pcs at Amazon
Yellow 12-10 gauge female terminal 16 pcs
360 pc assortment at Amazon
Buy:
Buy fuseholders
Fuse blocks at Amazon
Electrical terminals
Din rail fuseholder
10 x 38 mm fuse
ANL fuseholder
Electrical terminals
Read circuit analyzer Test outlet with circuit analyzer
This is first line troubleshoot when...
> When gas water heater or gas appliance plugs into outlet, the polarity and ground must be correct.
> When electrical devices, and appliances do not last very long, check outlet for polarity and ground issues.
> When household timers go bad quickly, or more than one timer has failed, test outlet with analyzer.

Circuit analyzer
Analyzer will not detect all electrical problems
Analyzer will detect basic polarity and grounding issues.

For example, gas water heaters that plug into outlet require correct polarity and grounding.
Postage equipment and many basic office tools and computers also require correct polarity and grounding
Buy:
Circuit analyzers at Amazon
Outlet polarity Household outlet polarity
Wires should always connect to correct blade.
The wide blade is Neutral. Narrow blade is Hot.
Many appliances and TVs have polarized plug. This is so Hot and Neutral can work correctly with electronics inside the device. If outlet is wired incorrectly, then appliances and timers, etc don't work as expected.
Resources
How to wire 240Volt outlets
How to wire 3-phase outlets
Wire connectors

Multimeter
Test for breaks in wire/ Test for voltage
Most appliance require 80% rated voltage to function correctly
Buy
Analog multimeter
Multimeters at Amazon
Klein multimeter
Electric testers at Amazon
Clampmeter for testing amp flow on line
Resource:
How to test and replace element
How to test thermocouple
Element tests for 120 volts
How to test wire
Safety when testing wires:
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.
Tape tester leads to wood sticks to keep hands away from power.
Use non-contact voltage tester before touching wires.
Never touch or lean into any made of metal.
Remove metal objects from pockets.
Do not use oxygen or fuel accelerants in same room as electrical repairs

Resource:
Basic house wiring

Non-contact voltage tester
Test for power without touching connectors
NEVER assume power is OFF

Buy:
Non-contact voltage tester Amazon
Electric testers at Amazon
Resource:
How to test electric power is off
GFCI receptacle120 volt 15 amp devices including GFCI, timers, switches, plugs, wifi controls etc can be installed on 15 or 20 amp breaker.

120 volt GFCI, outlet, receptacle that is rated 20 amp can be installed on 20 amp breaker only, but NOT on 15 amp breaker.  
Buy
15 amp GFCI
20 amp GFCI
Buy
Basic electric book
Home plumbing/ electrical codes
Basic electric book
Or learn about basic household electricity... use and search my site/
Resource
Safe electric wiring
Basic house wiring

Use outlet tester to check for correct wiring on any 120 volt straight-blade outlet.
Buy:
Klein testers
Outlet tester
Circuit breaker finder
Electric usage monitor
armored cable
Non metallic flexible cables must carry ground wire, but do not have hazard of short circuit causing injury from shock.

Armored steel cable can be used as a grounded connection, and will protect wires from damage. Metal can be energized from an insulation failure.

All conduit ...metal, plastic ... flexible and rigid ... must be attached to structure, and attached to enclosures, boxes.
Movement, damage and deterioration are major cause of electrical failure.
Buy:
Non-metallic flexible conduit
Power whip
Armored cable
Southwire armored cable cutter
Pull boxes
Southwire armored cable cutter
Electrical tools must be insulated.
Always best to disconnect power, but insulation failure, lack of proper grounding, grounded neutral, lack of GFCI, out-of-code wiring, generator operating without transfer switch, and other problems still pose a risk to anyone working on electric power ... even when breaker is off.

Buy:
Electrician tools kits
KLEIN TOOLS
Tools kits
IRWIN tools
KNIPEX
Connect wire to screw terminal
Use only 600 volt solid copper wire.
Do not use stranded wire or extension cord.
Do not use solder anywhere on residential 120-240 volt wiring.
Attach electric installation to structure. Tighten screws very tight against wire.

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

Resources:
How to twist wire
How to select and install twist-on wire connectors
Lever switchWeatherproof lever switch on outdoor lights
Safely operate outdoor toggle switch
Replaces outdoor cover
Install over top of ordinary switch
Works with single-pole, double-pole, 3PST, 3-way, 4-way switches etc
Use weatherproof box for outdoor
Can be used indoor or outdoor

Buy:
Best choice: Cantex lever switch
Outdoor lever switches at Amazon
Lever switches

Resource
Cantex-toggle-switch-covers.pdf
Cantex-PVC-junction-boxes.pdf

Treminals

Terminals

Buy:
Terminal kit
Blue for 16-14 wire
Yellow for 12-10 wire

Resource:
How to install terminal
Push on wire connectors

Push-on wire connectors in place of twist-on connectors

Buy:
Push on wire connectors Amazon
Red 3P connector for 10-14 gauge wire
Lever connectors for stranded wire at Amazon

Use nipper instead of pliers or screwdriver for removing staples (and nails). Do not damage cable or wires inside cable.

Code
-Cable SHALL BE secured without damage to the outer covering. NEC sec. 336-15
Buy
End cutting nippers at Amazon

 


When removing insulation from wire, do NOT score or put cuts on surface of copper wire. Doing so increases resistances on wire and creates weak point.
Buy tools:
Wire strippers at Amazon
Linesman pliers
Pro linesman plier
Needle nose pliers
End cutting nippers at Amazon

Weather resistant plastic box for outdoor extension cord connections, Christmas lights, outdoor power strip etc . Not for connecting wires with wire nuts®, or in-wall wiring, but can be used indoors to organize extension cords, power strips etc.
Weather resistant is not weatherproof or watertight. Use enclosures rated IP65 and IP67 for waterproof.
Extension cords cannot be used for permanent wiring.
Buy:
Large-medium-small electric cord box
Socketbox
Raintight enclosures
Water-tight cord lock
Resource: Enclosures and boxes
Electricity leaves power plant What is 3-phase electric: power plant to end user
Basic house wiring

Support the economy:
Buy water heaters from my associate links:

50 gallon Gas water heaters at Amazon
40 gallon gas water heaters at Amazon
50 gallon Electric water heaters at Amazon
40 gallon electric water heaters at Amazon
Hybrid / heat pump/ water heaters at Amazon

Resources:
How to install gas water heater
How to install electric water heater
Troubleshoot gas water heater
Troubleshoot electric water heater
Point of use water heaters
Buy
Industrial electric

Industrial supplies

Tools and home improvement

Home and garden

Hayward pool
Pentair pool

Southwire electric
Buy
Tools

DEWALT
Black and Decker
Stanley
SKIL
Makita
Porter-Cable
Bosch

Irwin Hand tools
Klein hand tools
Fluke electrical testing
Dremel hobby tools

Campbell Hausfeld air powered
Tekton automotive

Powerbuilt automotive
Saws and saw blades
box timers Resource:
Compare box timers
DPDT timers
Intermatic
Control water heater w/ Z-wave
Intermatic control centers Resource:
Intermatic control centers: and parts
Digital control centers and parts
Tork control centers and parts
Subpanels
All control centers and parts
Enclosures
programmable timer Resource:
Programmable timers
Countdown timers
Off delay timers
On delay timers
Timer modules
Din rail
Twin & one-shot
Woods
Intermatic
Tork
Low voltage power packs Recirculation systems
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Amazon
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