Color-code for residential wire <> for easy identification
10ga for 30 Amp circuits
14ga for 15 Amp circuits
12ga for 20 Amp circuits
Color-code for residential wire <> for easy identification |
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| Back to: gather materials for installation | Orange 10ga for 30 Amp circuits |
White 14ga for 15 Amp circuits |
Yellow 12ga for 20 Amp circuits |
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Basic electric formula: Volts x Amps =
Watts ++  for safety,
wires can carry 80% of rated load |
 Household NM-B Wires are color-coded so inspectors/ electricians can easily identify which wire is used during construction |
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. Circuit breaker and wire size must match Chart on right shows that 30 amp breaker matches 10 gauge copper wire. Do not use aluminum wire. Copper wire is safe. Aluminum wire expands when electricity travels through wire. Expansion causes loose connections and fire hazard. If breaker is oversized for wire, then breaker can let too much electricity travel through the wire. Wire can overheat and cause fire. If you suspect wiring is not correct, call electrician. Absolute electrocution danger when removing cover off main panel. More information below. Main breaker terminals are still Hot when main breaker is turned off. |
 Larger image with wire types, temperature, long length Maximum wattage for houshold NM-B and DU-F wires Wire diameter, weight, resistance |
 Larger image |
Use
in-line fuse when connecting 2 different gauge wires Connect 12 gauge wire to 10 gauge wire. Illustration shows smaller 12 gauge wire connected to larger 10 gauge wire. 10 gauge wire 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. Use busman fuseholder with 20 amp fuse. Fuse will protect entire length of 12 gauge wire. Connect fuse to Hot wire. Not necessary to put fuse on Neutral If the 12 gauge wire was wired for 240V, then fuse is necessary for both hot wires. Always make connections inside a box with cover See fuseholder |
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How
to figure correct size wire and breaker Use chart on left to select wire and breaker Use the 80% rule when calculating Capacity. When wires and breakers operate at 100%, they get warm. Warm wires mean amp loss and potential fire hazard. Warm breaker means that breaker will not last as long, and busbar could suffer damage from heat over time. 14 ga wire ++ rated for 120 Volts x 15 Amp = 1800 Watts x 80% = 1440 Watts safe maximum 12 ga wire ++ rated for 120 Volts x 20 Amps = 2400 Watts x 80% = 1920 Watts safe maximum 10 ga wire ++ rated for 240 Volts x 30 Amps = 7200 Watts x 80% = 5760 Watts safe maximum Wire size chart with distances Look at watt rating of appliance, or motor or tool Volts x amps = watts Watts divided by volts = amps Volts squared divided by watts = ohms Electrical formulas |
 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 overheating problem occurs over time. Circuit breaker will not last as long, and damage can occur to busbar. See basic water heater circuit How to replace circuit breaker 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. Figure Volts Amps Watts for water heater |
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Ordinary
Main panel for
home has 120 volt and 240 volt circuits. This is called single-phase electric power. Phasing is determined by the power company. - Each 120 volt circuit can include up to 12 outlets, and supply power to lights inside a room. - Generally each 120 volt circuit sends power to one area of home. This is because the wire leaves breaker box and goes to first junction box inside a room. From the junction box, the wire splits off and goes to each individual box, jumping from box to box until the final box is reached. So each box will have 1 black hot wire, 1 white neutral wire, and 1 ground wire that connect back to main breaker box. - Some circuit breakers are dedicated to 1 specific appliance. For example the kitchen microwave is usually wired to 1 circuit breaker and no other outlets or lights are connected to that breaker. This is because microwave draws so much amperage. That is called dedicated circuit, and dedicated breaker. - Each 240 volt circuit is usually dedicated to one appliance. For example electric water heater is connected to 1 240 volt breaker. The electric dryer is connected to another 240 volt breaker. The heat/AC is connected to another 240 volt circuit breaker, and so on. See inside main breaker box How to replace circuit breaker How to install subpanel Figure volts amps watts for electric water heater |
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E-mail: info@waterheatertimer.org Site map |
