Wire ampacity.

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Old 10-26-05, 03:45 PM
pyrotechjci
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Question Wire ampacity.

Hello all. I have looked in the NEC 70 to try to determine the size of wire I need for changing gas appliances (stove, water heater and furnace) over to electric but was not able to make much sense of the ampacity section. What I really need to know is what size wire I need for the repsective current draw of each appliance. For instance #12 is good to 20A etc. Also, if the max current rating for a device is 30A is that also the size of the breaker I need or so I need to leave some wiggle room to prevent false trips (for instance 30 A device - 40 A breaker)? Thanks for any help you can provide.
 
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Old 10-26-05, 04:05 PM
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Originally Posted by pyrotechjci
Hello all. I have looked in the NEC 70 to try to determine the size of wire I need for changing gas appliances (stove, water heater and furnace) over to electric but was not able to make much sense of the ampacity section. What I really need to know is what size wire I need for the repsective current draw of each appliance. For instance #12 is good to 20A etc. Also, if the max current rating for a device is 30A is that also the size of the breaker I need or so I need to leave some wiggle room to prevent false trips (for instance 30 A device - 40 A breaker)? Thanks for any help you can provide.
There are many variables on size of wire for appliances. Would need to know state/county codes. Check with your local code enforcement officer for the info on that. As far as giving yourself "a little wiggle" on sizing your breakers slightly over the wire size, the answer is no, never do that. You would then stand a risk of wire insulation failure and possibly a fire/short circuit doing this.
 
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Old 10-26-05, 04:17 PM
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1) Don't think of it as "changing over". You cannot change from gas to electric. Nothing used with gas will be close to compatable with the same appliance using electric. Think of it as re-feeding the appliances.

2) There is NO one section that says specifically this wire is good for this applaince. Ranges are in one section, water heaters in another, etc. Most are based on NEC 310.16 where overcurrent protection is concerned.

3) Get a list of all the appliances you need to re-feed with their respective amperage requirements. This is the only place to start.
 
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Old 10-27-05, 10:32 AM
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Rule of thumbe (check plates to be sure)

Range: 8/3 or 6/3, on 40 or 50A breaker.

Cooktop, 10/3 or 8/3, on 30 or 40A breaker.

Wall oven 8/3 on 40A

Dryer 10/3 30A

WH 10/2 on 20A or 30A

Electric Furnace, what I have seen, 60 or 100A, #4 wire.
 
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Old 10-27-05, 11:22 AM
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But then again. It is getting more and more common seeing a four wire plug and recepticle up on the cook top and ranges. So keep this in mind as well.
 
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