220v wiring: 3 wire or 4 wire?


Old 04-21-07, 08:36 PM
ben is offline
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220v wiring: 3 wire or 4 wire?

Hi all,
I am installing a new central air conditioning and I need some help with the wiring. Both out side unit and inside air handler uses 220 volt.
On of the electrical book that I was reading states that the new code requires 4 wires for all new 220 volt installation for ranges. But they I could not find anything for central AC wiring.
Does this new 220 volt wiring requires a 4 wire(2 hot + a neutral conductor + ground) or a three wire(2 hot + one ground) for both wiring?

Thanks in advance
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Old 04-21-07, 08:44 PM
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ranges and dryers reqauire a 120/240 volt circuit.AC units generally only need a 240 volt circuit so no neutral is needed.

120/240 would be the 4 wire

240 would be a 3 wire
Old 04-21-07, 08:56 PM
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Each 240V A/C and air handler that I've installed has only needed 3-wires.
Old 04-22-07, 04:15 AM
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Many local codes now require you to also install a 120 volt outlet for service, adjacent to the outdoor condenser, and also adjacent to an indoor air handler if it is in the attic. These might need to be on a separate circuit, probably not off a 4 wire 120/240. Check with your inspector to see what they require.
Old 04-22-07, 08:17 AM
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actually that is NEC code 594tough. Without looking it up, I believe the service recep must be within 25 feet of the unit. the required gfci receps on the front and rear of a house often (usually) cover this requirement.

but it is a good point.
Old 04-22-07, 09:42 AM
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An AC unit is probablly not going to be the correct amperage for a general purpose rec. Even if by chance it were, putting a general purpose rec on the same circuit, and using one leg and an extra neutral for this would be IMHO poor workmanship. The intention of this rec is for servicing the equipment. If the breaker had tripped, a service worker might want to check out the unit before turning back on the breaker.

I agree that any general purpose rec installed within 25 feet of the equipment does satisfy this requirement.

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