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Is this safe?
Answer: Yes. It is safe
Resource:
Safe electric wiring
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My circuit breaker is 20 amp, but
outlets
and switches are 15 amp. Is this safe? Answer: Yes. It is safe Resource: Safe electric wiring |
| Use only 600 volt wire. Lamp cord, extension cords are not rated 600 volt. Use copper wire only. Aluminum wire is fire risk and should be avoided or installed by professional. 30 amp breaker use 10 gauge / 120-240 volt 30 amp outlet can be installed on 30 amp breaker only/ use 10 gauge wire ... cannot be connected to 15-20-40 amp breaker.  Orange/ #10 gauge wire, with ground ... 30 amp capacity. Safe maximum: 30 x 80% = 24 amps. Buy: 10-2 gauge/ 30 amp 10-3/ 30 amp Southwire electric tools |
Yellow
12 gauge 20 amp 120 volt 20 amp outlet can be installed on 20 amp breaker, but not 15 amp breaker/ use 12 ga wire. ... cannot be connected to 30-40 amp breaker. 1  Yellow/ #12 gauge wire, with ground ... 20 amp capacity. Safe maximum 16 amps. Buy: 12-2 gauge/ 20 amp 12-3/ 20 amp NMB is house wiring UF is underground Rolls of stranded wire HOOK UP Wires |
 Multimeters Voltage is tested across two separate wires. Ohms or resistance is tested across both ends of same wire. Amperage is tested along one or two points on same wire. Buy: Analog multimeter Multimeters at Amazon Klein multimeter Electric testers at Amazon Clampmeter for testing amp flow on line |
40-50
amp breaker use 8 gauge / 240 volt 40 amp outlet can be installed on 40 or 50 amp breaker only  Buy: 8-2 wire Southwire electric tools NMB is house wiring UF is underground |
 Protect wiring from damage Use nipper instead of pliers or screwdriver for removing staples (and nails). Do not damage cable or wires inside cable. -Code says: Cable SHALL BE secured without damage to the outer covering. NEC sec. 336-15 Buy End cutting nippers at Amazon |
 Electrically insulated tools When removing insulation from wire, do NOT score or put cuts on surface of copper wire. Doing so increases resistance and heat on wire and creates possible weak point. Buy tools: KLEIN TOOLS Wire strippers at Amazon Electric Wire Stripping Machine Linesman pliers Utility knife at Amazon |
| What are amps: Amps are a currect of electrons. Electricity is made up of volts and amps. Volts x Amps = Watts is basic formula. Watts are the overall power requirement for operation of a Load (light, fan, motor, toaster etc). Volts are the force that pushes the current of electrons (amperage) along the conductor (wire). Electric reliability is the standard that ensures voltage remains generally unchanged throughout the day ... while amperage (flow of electrons) rises and falls as Loads turn ON and OFF ... with more amperage being used when loads are turned ON. If voltage on the grid drops below nominal, then Loads will will draw more amps. Why? Volts and amps are inversely proportional. If volts go down, the Load still consumes the same wattage, so it must draw more amps. More amps flowing on the wire meets higher resistance because each wire size has a maximum amp rating. If too many amps (electrons) are flowing down the wire, it will cause heat that can damage motors, exceed breaker rating ... increase fire hazard and generally waste energy. |
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Franklin asks: My
circuit breakers are 20 amp, but light switches, outlets and the
wall timer are rated for 15 amp.
Is this safe? Isn't this backwards won't a 15 amp outlet pulling 20 amps melt if on a 20 breaker circuit? |
| Gene Answers: Yes, it is safe, assuming load is less than 15 amp. Code permits 15 amp or 20 amp switches, outlets, GFCI, timers etc on a 20 amp breaker. Safe maximum for 20 amp breaker and 12 gauge wire is 16 amp ... why? ... Safe maximum is 80% ... so 20 amp breaker x .80 = 16 amps. Applies to residential electric. Commercial code can be different. Just because the
breaker is rated 20 amps, doesn't mean there are 20 amps flowing on the
circuit.
If no loads (light, fan, motor etc) are running, then no amps are flowing. If a 7.2 amp refrigerator is plugged into outlet rated for 15 amp, then the refrigerator will pull 7.2 amps when running. If a 500 watt TV and 100 watt light are also on same 20 amp circuit breaker as refrigerator, then they will pull additional 5 amps (600 divided by 120 volt) from circuit breaker. This means the 20 amp breaker is letting 12.2 amps flow onto the circuit, but those amps are not flowing though the refrigerator outlet unless the TV and light are plugged into same outlet. More likely the TV is plugged into separate 15 amp outlet, and light is controlled by a separate 15 amp switch, and each load is less than 15 amp. The 20 amp breaker rating is the maximum number of amps that are allowed to flow through the circuit breaker before the breaker trips.  For
120 volt circuits: It is permitted by code to install either 15 amp or 20 amp switch, outlet, dimmer, timer, GFCI, AFCI etc on a 20 amp breaker. Code allows you to plug orange 14 gauge 10 amp extension cord, or brown 7 amp lamp cord into the 15 or 20 amp outlet. Homes often have 15 amp switches and outlets, and nearly all household wall timers are rated 15 amp, with only a few wall timers that are rated 20 amp. Resources: Programmable wall timers Countdown timers Plug in timers Ratings for each device are embossed into the device, or appear on packaging or instruction manual. Generally, 20 amp devices cost more than 15 amp since they must be made of heavier materials to handle the higher amperage. Note: 15 must be 15.
If the circuit
breaker
is 15 amp, then only 15 amp switches and outlets,
gfci etc are permitted.
20 amp switches, timers etc are not permitted on a 15 amp breaker. Of course it's good to have everything exact in your home, but nobody is coming around and checking unless a home inspector is involved, so no urgency to take apart your electric boxes. The rule of thumb is, if things are working fine and nothing feels hot or is smoking or blowing the breaker, then it's working fine so don't mess it up.  15 amp is safe as long as the load is less than 15 amp. You cannot put a 120 volt 1 HP
motor that draws 16 amps on a 15 amp
switch. For this project a 20 amp breaker, 12 gauge wire and 20 amp
switch would
be required, shown Fig-1. By code, the neutral
wire is never switched on-off.
-Safe maximum for ordinary switch when used for motor is 80% rated value. Maximum load on 15 amp switch is 15 amp or 10 amp 1/2 Hp motor ... and maximum for 20 amp switch is 20 amp or 16 amp 1 HP motor. Motor loads will shorten life of ordinary switch. Use heavy duty motor switch or contactor. Buy: Motor switch Resources Cooper-switch-rating.pdf Amp rating for wire and motors Contactors and relays -All household wiring, no matter what size circuit breaker or fuse, must have 600 volt cable and wire. Extension cords are rated 150-300 volts and are not approved for permanent household wiring. Damaged wire is not permitted and must be replaced. Resource: Color code wire -All connections and devices must be installed in electrically rated enclosure (box) with matching cover. Homemade enclosures are generally not permitted. Missing covers, ventilation holes, and concealed boxes are not permitted. Resource: Types of enclosures and boxes Electric-code-for-enclosures |
| For
240 volt circuits: It is code to use 15 amp or 20 amp switch or outlet on 240 volt 20 amp circuit as long as load is less than 15 amp. 240 volt Switches: Cheap switches are rated 120 volt and can only be used for 120 volt. Better grade switches are rated 120-277, meaning they can be used on 120, 208, 240, 277 volt circuits. Resource: What is 277 volt Switches that are rated 240 volt are always double pole with 4 screw terminals. It it code to switch either one or both legs of 240 volt circuit. Buy: 30 amp DPDT switch 240 volt plugs and outlets have different configuration for the prongs than 120 volt outlets. Window air
conditioners are good example of 240 volt outlets inside a
home.
Note that the plug for the 15 amp air conditioner has two flat horizontal blades plus a ground prong. Note also that the 15 amp plug can fit either the 15 amp or the 20 amp outlet, while the 20 amp plug can only fit the 20 amp outlet. So if the 240 volt
double breaker is 20 amp, then you can install a 240 volt 15 amp or 20
amp outlet ... but if the air conditioner is 20 amp, then the outlet
must be changed to 20 amp.
If 240 volt air conditioner is rated 20 amp, but the breaker is 15 amp with 14 gauge wire, I recommend buying 15 amp air conditioner vs changing breaker and wire to 20 amp and 12 gauge.   Footnote: The plugs
and connectors are rated 250 volt and not 240 volt. Household voltage
is listed as 120-240 volt, but actual on-site voltage
can be higher or lower than standard, with 250 volt nearing the top
range of expected voltage. The higher voltage means less amperage is
needed to meet load demand. Lower amperage means higher efficiency.
This means higher voltage can run slightly cooler with
higher efficiency, and since wires and cables are rated 600 volt, then
there is no problem as long as appliances can accomodate the
voltage. Look at rating plate on each load. You cannot connect 120 volt
appliance to 240 volt circuit or the appliance will burn up.
Resources: Are both sides of 20 amp 240 volt double breaker 20 amp? Answer yes. How to wire 240 volt outlets |
| Why does code allow 15
amp outlets, switches etc on 20 amp breaker? 1) Remember the 20 amp breaker serves an entire circuit, up to 12 boxes, and each box can have a 15 amp timer, switch or outlet etc. The total load across all 12 boxes on circuit cannot exceed the 80% safe maximum for a 20 amp breaker = 16 amps. The same is also
true for a dedicated breaker that serves only one
appliance, for example a microwave etc:
 2)
Very few lights or plug-in appliances consume 15 amp .... 15 amp x 120
volt = 1800 watts ... nor consume 20 amps ... 20 amp x 120 volt = 2400
watts.Even microwaves, space heaters, tea kettles, toaster oven etc are rated maximum 1500 watt ... and by code, all 1500 watt appliances should be installed on a 20 amp dedicated breaker that serves no other load. The 1500 watt microwave consumes 12.5 amp (1500 divided by 120 volt). Running a 12.5 amp microwave means a 15 amp outlet will work fine for any 1500 watt load as seen Fig-2. 3) The distance from circuit breaker to microwave is part of the reason the breaker and wire can be rated more amps than outlet or switch. There is a drop in voltage when wires get longer than 25 feet. Volts x amps = watts. The appliance draws 1500 watts, so the formula shows if volts drop, the amperage on wire must go up to meet load demand. More amperage means more heat on wire and energy loss. Typically the loss is not important until wire exceeds 100-150 feet, and then the next size larger wire should be used. To avoid power inefficiencies and overheating caused by distance, the electrical wiring code is designed for overcapacity, which means the 20 amp breaker and #12 wire are oversized for the job, and not intended to carry the full 20 amps.  4)
Related to length of wire and overheating is the 80% safe maximum
calculation for circuit breakers. For example, a 20 amp breaker has 80%
safe maximum of 16 amps (20 x .80 = 16).Add up wattage of all loads on the circuit and divide by 120 volt to get total amp draw for that circuit. If total load is below 16 amps then circuit is solid. The safe max rule ensures that wire and breaker cannot get hot and trip. Continual overheating a breaker will cause it to come loose from busbar, start arcing and then burn out, damaging the busbar so no breaker works in that slot. Using correct wire and breaker size are the answer. Calculate for the dedicated 1500 watt microwave circuit and divide by 120 volts and you get 12.5 amps, which is below both the 16 amp safe maximum and below the 15 amp outlet rating ... and by code, microwaves are required to have dedicated breaker with no other loads sharing same breaker. Resource: Safe electric wiring How to replace circuit breaker |
  30
must be 30Note: 30 amp outlets can only be used with 30 amp breaker with 10 gauge wire. Code does NOT permit 30 amp outlets on any other size breaker such as 40-50 amp. Buy: Dryer cords 30-40 amp Range cords 40-50 amp  ResourceHow to wire 240 volt outlets 30 amp switch can be used on 15-20-24 amp loads. Max amperage for 30 amp switch is 24 amps. Can be used on 120, 208,240, 277 volt ... check rating 1.5 Hp @ 120 volt, use 12 ga wire. 3.0 Hp @ 240 volt, use 10 gauge wire. Buy: 30 amp 2-pole switch 30 amp industrial grade Leviton 3033 switch 30 amp 3-way switch |
 Household NM-B Wires are color-coded so inspectors/ electricians can easily identify which wire is used during construction 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.  |
Match
wire size and breaker amp rating 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. Safe maximum of amp draw on a breaker is 80% rated value of breaker. 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. If breaker is oversized for wire... fire danger Breaker can let the voltage push too much amperage (current of electrons) through the matrix (atomic structure) of the wire. The natural resistance of the copper wire creates a 'friction' that overheats the wire and causes fire. Call electrician if you suspect wiring is not correct, Main breaker terminals are still Hot when main breaker is turned off. Absolute electrocution danger when removing cover off main panel. More information Use 600 volt solid copper wire only Do not use stranded wire inside main breaker box or any permanent box. Stranded wire can be used for connectors and plugs, but comes loose under screw terminals of breaker, switch, outlet, or timer etc when heat on wire causes expansion and contraction of wire. Do not use extension cord for permanent household wiring Extension cords are used for connectors and plugs only. Read about extension cord code Buy: Southwire at Amazon Resources: How to replace circuit breaker Southwire Romex NM-B specification and usage manual Southwire UF-B specification and usage manual Ampacities for TW and UF insulated wires: NEC table 310-16 |
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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 considerably more than copper, and will force wires and connections to come loose from terminals, wire nuts, outlets, switches etc |
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20 amp GFCI
 |
120 volt GFCI outlets
come in 15 and 20 amp. The 15 amp GFCI can be installed on 15 or 20 amp breaker. The 20 amp GFCI must be installed on 20 amp breaker. 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). GFCI outlets are installed inside wall boxes and are strictly for 120 volt, but GFCI circuit breakers that are installed inside the breaker box (service panel) come in 120 volt or 240 volt varieties. GFCI breakers will protect the entire circuit. Caution: just 1 GFCI per circuit to ensure correct function. Multiple GFCI on same circuit can cause frequent resets and failures. More detail With 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.
Buy:
portable
gfci15 amp GFCI 20 amp GFCI |
20 amp timer |
Most
wall
timers are 15 amp, but a few are rated 20 amp Honeywell RPLS730B heavy duty timer/ 7-day programmable Single-pole/ requires neutral wire/ heavy duty 20 amp ... 120 volt / 2400 watt LED, CFL, fluorescent/ 1200 watt incandescent, halogen/ motor loads up to 1 Hp. No minimum wattage.  Buy/ requires neutral Honeywell RPLS730B white/ RPLS731 almond Resources: RPLS730 manual RPLS730B sell sheet More programmable timers |
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