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Old 06-10-2011, 10:06 PM   #1
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Roof A/C disconnects and service receptacle


As part of a reroof, I'm adding adding a service receptacle, adding a disconnect for the rooftop A/C, and adding a disconnect for a future swamp cooler. These will be mounted on an exterior sidewall section of T-1-11 (plywood) siding with the back side of the plywood open to the attic, i.e dry conditions.

For the service receptacle, what's the correct way to bring/secure the 14/2 NM cable into a surface mount outdoor box through the back hole?
The box sits 1/16" off the surface due to the mounting tabs.

For the A/C and swamp cooler disconnects, I'm using Square D unfused disconnect 3R boxes.
These sit 1/4" off the surface and have knockouts on the back side

For the A/C, the cable is 4/2 AL SE.
What's the correct way to bring/secure the cable into the disconnect box using the rear K.O.s?

For the swamp cooler, the cable is 12/2 NM.
What's the correct way to bring/secure the cable into the disconnect box using the rear K.O.s?

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Old 06-11-2011, 06:37 AM   #2
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Roof A/C disconnects and service receptacle


Are you an electrician or a roofer?
Is this a job for a customer?

You are asking VERY basic questions here. If this is a job for a customer you should not be doing something so far out of your expertise.

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Old 06-11-2011, 11:17 AM   #3
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Roof A/C disconnects and service receptacle


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Originally Posted by Speedy Petey View Post
Are you an electrician or a roofer?
Is this a job for a customer?
Neither. I'm my own worst customer.

Quote:
Originally Posted by Speedy Petey View Post
You are asking VERY basic questions here.
While they may sound like a VERY BASIC questions, they actually have a couple of fine points I'd like confirmed. I asked VERY BASIC questions without a lot of detail and not injecting my own conclusions hoping for VERY BASIC answers.

I've read a lot of your posts and you're one of the most knowledgeable electricians out there, but sometimes you're quite abrasive. Is the Sopwith being temperamental again?

fine point #1-
Is the inside of an exterior surface mounted box considered a dry location? If not, then I can't use NM in it. Now that I think about it, it has to be a dry location - at least above the location of the electrical parts. Thanks.

fine point #2-
If cable is sleeved through conduit into a box, is securing the cable before it enters the conduit all that's required?
cable---staple--conduit--box
IOW, there's no need to worry about clamping it to the box because the conduit is securing/supporting the cable.
334.15(C) talks about it, but that section is for cables on walls of basements, not attics. Now that I think about it, it's reasonable to apply the wiring method described in that section to any situation. Thanks.

For the service receptacle, I could put a NM clamp in the back of the box and caulk it. The clamps aren't exterior rated. I've done that under the eaves and didn't feel bad about it because the box never gets wet, but this box is on the roof and will be subject to weather. Or I can sleeve it in conduit to make the transition between attic and exterior.

For the A/C disconnect, I could put an NM/SE clamp into the back of the box. Again, the clamp is typically not exterior rated although the cable is. I'd have to cut a fairly large hole so the clamp will clear the siding, which will require lots of caulk or duct seal to conform to the irregular shape of the clamp. Or I can sleeve it in conduit to make the transition between attic and exterior.

For the evap disconnect, the 12/2 has to run outside for 1/4" in a wet location to enter the box. Its a violation no matter how you look at it, so I'd like to know if there's an easy way to eliminate that. The only thing I could come up with to meet code is to splice a few feet of 12/2 UF onto the NM and feed the UF into the box. I'm inclined to ignore the 1/4" exposure and ... sleeve it in conduit to make the transition between attic and exterior.

Conclusion. I'll use conduit to make the attic-exterior transitions and plug the box end of the conduits with duct seal. I'll just ignore the 1/4" of NM in a wet location on the evap disconnect since the conduit will be plugged in the box, and open to the attic to breathe - no condensation.

Anybody have any better ideas?

BTW, I'm trying to clean up part of a mess that the original builders left 20 years ago. The A/C SE cable came out of a roof jack. They skinned the A/C SE cable for about 6', popped it out of a roof jack, and sleeved it through 3/4 liquidtight with metal core into the A/C unit. There was no connector on the roof jack end of the liquidtight, they just stuck the liquidtight in the jack, taped it down, and tarred it.

Oh yeah, they managed to cram the thermostat cable into the liquidtight too. I'm adding another 1/2" liquidtight run for the thermostat cable.
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Old 06-11-2011, 11:40 AM   #4
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Neither. I'm my own worst customer.
Then I apologize.
I got the impression you doing this for a job for someone.
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Old 06-11-2011, 02:00 PM   #5
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Roof A/C disconnects and service receptacle


I guess it did sound like a hack roofer with a 72 Buick and a trunk-o-tools. But you could have cut me some slack since I spell correctly and compose coherent sentences.
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