How
to wire 240 volt outlets
Watch
for screw terminal coloration: Brass for Hot, Silver for Neutral, Green
for ground
Some outlets do not have color-coded screws.
Rule of thumb: the hot wires connect to side of outlet.
Some outlets do not have color-coded screws.
Rule of thumb: the hot wires connect to side of outlet.
 Larger image |
Image shows 120Volt
line and 240volt line. Both circuits have ground wire. Each 120 and 240 require two wires to complete circuit. 120V requires 1 hot and 1 neutral 240V requires 2 hots Some 240Volt lines have additional neutral wire. Neutral not necessary to complete 240Volt circuit. Some 240Volt lines have white and black instead of red and black See basic circuits See inside main box Wire sizes |
Separate wires for testing.
Tape tester leads to wiood sticks, and stand on dry wood boards.
Test each wire to bare ground. If both wires test for power to ground, the circuit is probably 240Volt.
Use multi-meter to confirm exact voltage.
Image shows 2 hot wires with ground.
2 Hot wires and 1 ground wire.
Hot wires can be red and black -or- white and black
Either hot wire can connect to either brass terminal
Notice color of screws when wiring 240Volt outlets
Green for ground
Hot1 and Hot2 connect to either brass screw
 Larger image |
240Volt outlet can
be wired for 120Volt Ordinary 120volt outlets have brass screws on one side for Hot wire, and silver screws on opposite side for neutral wire. |
Hot wires can be red and black -or- white and black
Either hot wire can connect to either brass terminal
Notice color of screws when wiring 240Volt outlets
Green for ground
Hot1 and Hot2 can connect to either brass screw
Green for ground
Silver for Neutral
Hot1 and Hot2 can connect to either brass screw
The extra wire is a neutral wire. Neutral is not necessary to complete 240volt circuit. Some appliances might require neutral wire to operate 120volt parts inside the appliance. This is rare with todays appliances and electronics.
Notice color of screws when wiring 240Volt outlets
Green for ground
Silver for Neutral
Hot1 and Hot2 can connect to either brass screw
2 Hot wires and 1 ground wire and 1 neutral wire.
The extra wire is a neutral wire. Neutral is not necessary to complete 240volt circuit. Some appliances might require neutral wire to operate 120volt parts inside the appliance. This is rare with todays appliances and electronics.
Notice color of screws when wiring 240Volt outlets
Green for ground
Silver for Neutral
Hot1 and Hot2 can be either color and can connect to either brass screw
10-3 w/g (with ground) NM-B indoor household wire
See wire gauges and charts
Notice that sometimes the screws are NOT color coded.
Rule of thumb is that Hot wires connect on sides of outlet. The outlet installs in typical one-gang box. Outlet can be rotated so ground is at top of bottom.
Notice that red hot wire and black hot wire can go on either side of device. Both hot wires in 240Volt household circuit are identical.
Image on left is from: Corner hardware
Note on the corner hardware site that it says maximum load on 12 gauge wire is 20 amps. This is misleading.
Electricians use 80% rule.
True that 12 gauge wire connects to 20 amp breaker, but electricians apply 80% rule to calculate load rating for breakers and wires.
20 amp breaker x 80% = 16 amps safe maximum for 20 amp breaker.
30 amp breaker x 80% = 24 amps safe maximum for 30 amp breaker
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1) Each 240Volt outlet sold at Hardware or Home Center will have amp rating.
For example some will be rated for 40 amps, and others for 50 amps etc.
2) Each appliance will have rating-plate located on side of appliance or inside door of oven, or back of dryer.
3) Formula: Volts x amps = watts.
Watts divided by volts = amps
Volts= 240Volts
4) Example: Double-oven wattage = 7000 watts.
7000 watts divided by 240Volts = 29.16 amps.
5) Figure breaker and wire size for double-oven:
Safe amximum for 30 amp breaker is 24 amps. So double-oven needs 40 amp breaker.
Use 8 gauge wire for 40 amp breaker.
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14 ga wire ++ rated for 120 Volts x 15 Amp breaker = 1800 Watts x 80% = 1440 Watts
12 ga wire ++ rated for 120 Volts x 20 Amp breaker = 2400 Watts x 80% = 1920 Watts
10 ga wire ++ rated for 240 Volts x 30 Amp breaker = 7200 Watts x 80% = 5760 Watts
Wire sizes
Wire size chart with distances
Electrical formulas
Figure volts amps and watts
