NM Wire Designation Suitable For 220 V Residential Use ?

Let me guess, 10#, 30amp, and now asking 220v question, is this a water heater?

As for 220v, yes even 240v too. :-P

You can check the NEC for actual codes. I'm guessing you'll need a double pole breaker at part of your material list.

imho,

tom @

| I understand that Copper No. 10 AWG is the correct wire size for a | circuit in a residence with a 30 amp circuit breaker. | | If the wire used has the typical NM designation, is the insulation rated and | suitable for | 220 V, as well as the conventional 110 V ?

The voltage rating should be printed on the wire. As long as the highest voltage between any 2 conductors does not exceed that rating, you should be OK. Typically NM and other wiring will be rated 300 volts or 600 volts. I have seen some rated 1000 volts. It's a matter of insulation quality, not conductor size.

You will need to be sure you have the right set of conductors for the type of 240 volt circuit you are putting in. Be sure you know whether the load needs a neutral wire or not. The typical air conditioner or water heater does not. The typical clothes dryer or kitchen range does. There are exceptions in some cases, so double check.

As others have pointed out, NM is fine voltage wise, but depending on your application, its temperature rating may not be sufficient (ie. central heat) in which case SE would be a better choice.

John

NM-B is rated to 90C. But is heavily restricted to the 60C applications, when rating for amperage.

So unless the OP is using the cable in nonresidential, extreme environments, he should be ok. But always referr to the NEC for specifics.

later,

tom @

True, but the question refered to using 10AWG NM in a 30A situation. Depending on what the actual usage is and, more specifically, what the ambient temp is, he might have to derate the NM. In a case like this he'd be better off with SE. In reality the NM would work fine, but for NEC compliance we need more specific information.

John