residential a/c feeder question

[skalumafla]

I was reading my 08 code book, but cant find where it says that the feed to the a/c unit has to be wired using MC. I have been asked many times why does it have to be wired in MC instead of Romex. Can someone point me in the right direction?

 

[mdshunk]

It's not a requirement, unless you have some really strange local amendment.

 

[quogueelectric]

I was reading my 08 code book, but cant find where it says that the feed to the a/c unit has to be wired using MC. I have been asked many times why does it have to be wired in MC instead of Romex. Can someone point me in the right direction?

The rx cannot be subject to physical damage that is why many people either change over to mc/bx or sleve the whip to the unit in greenfield/carflex it protects the wire from the monsters in the house.

 

[Dennis Alwon]

I was reading my 08 code book, but cant find where it says that the feed to the a/c unit has to be wired using MC. I have been asked many times why does it have to be wired in MC instead of Romex. Can someone point me in the right direction?

FWIW, I have never seen a residential a/c unit wired with mc cable and rarely have seen it with ac cable (BX). Once it leaves the house the units are either wired with sealtite but more commonly today with carflex.

 

[stickboy1375]

FWIW, I have never seen a residential a/c unit wired with mc cable and rarely have seen it with ac cable (BX). Once it leaves the house the units are either wired with sealtite but more commonly today with carflex.

I've piped a few with emt, but generally NM to the disconnect and carflex to the unit.

 

[Minuteman]

I've piped a few with emt, but generally NM to the disconnect and carflex to the unit.

Me too. But it sounds like that when the '08 kicks in, I will have to covert to UF before the disconnect.

 

[Dennis Alwon]

Me too. But it sounds like that when the '08 kicks in, I will have to covert to UF before the disconnect.

Huh-- what you say...

 

[infinity]

The only advantage is that the MC can be used at the 75 degree ampacity versus the 60 degree with NM cable. This may allow for a reduced conductor size when using #10 or larger cables.

 

[LLSolutions]

What type of A/C unit are we talking about it, blower in an attic? compressor outside, or window type. NM should be fine unless your locality has some specific requirements.

 

[Minuteman]

Huh-- what you say...

We are still in the '02 cycle in OKC. I know many of y'all disagree, but they have been allowing us to stub the NM outside. (Also run NM inside of conduit above ground). When the '08 is adopted here, 334.12(B)(4) will change all that.

 

[Dennis Alwon]

We are still in the '02 cycle in OKC. I know many of y'all disagree, but they have been allowing us to stub the NM outside. (Also run NM inside of conduit above ground). When the '08 is adopted here, 334.12(B)(4) will change all that.

I really am not sure that the 08 will stop you from running NM to an outdoor disco. At least around here they don't. From the disco to the a/c you would have to run wire suitable for wet location.

 

[Minuteman]

I really am not sure that the 08 will stop you from running NM to an outdoor disco. At least around here they don't. From the disco to the a/c you would have to run wire suitable for wet location.

The dude that held the '08 CEU course was sure that 334.12(B)(4) would be interpreted that way.

 

[Dennis Alwon]

The dude that held the '08 CEU course was sure that 334.12(B)(4) would be interpreted that way.

Around here many ec use outdoor panels. That would mean every homerun would have to be in UF cable. I don't see it being enforced that way here but I always wondered why it wasn't.

 

[Minuteman]

Around here many ec use outdoor panels. That would mean every home run would have to be in UF cable. I don't see it being enforced that way here but I always wondered why it wasn't.

I hear you. If that becomes enforced here that way, I suppose I will run a home run to a j-box in the attic and then change over to UF before stubbing out to the RT panel.

 

[Dennis Alwon]

I hear you. If that becomes enforced here that way, I suppose I will run a home run to a j-box in the attic and then change over to UF before stubbing out to the RT panel.

Yeah , and I think if that what the codes intent was then it has created a worse install by making us add more splices.

 

[Minuteman]

Yeah , and I think if that what the codes intent was then it has created a worse install by making us add more splices.

True that! :roll:

 

[stickboy1375]

The dude that held the '08 CEU course was sure that 334.12(B)(4) would be interpreted that way.

So all outdoor fixtures, receptacles shall be fed with UF also?

 

[peter d]

So all outdoor fixtures, receptacles shall be fed with UF also?

I don't think those could be classified as wet locations. The inside of a sealtight whip to an AC sure is, but a bell box or outdoor light can be sealed to prevent moisture from entering.

 

[stickboy1375]

I don't think those could be classified as wet locations. The inside of a sealtight whip to an AC sure is, but a bell box or outdoor light can be sealed to prevent moisture from entering.

But NM run into the back of a disconnect cannot? Thats kinda where I got lost.

 

[peter d]

But NM run into the back of a disconnect cannot? Thats kinda where I got lost.

I don't get it either, but I'm trying to use common sense, which is outlawed in this country.