Thread: Exterior Service Equipment Panels, A/C disconnect panel boxes

For new construction , should the builder NOT seal the service equipment panel and the A/C disconnect boxes to the brick veneer. I'm thinking that the Builder sealing the back of the panel and disconnect boxes to the brick veneer prevents proper air gap spacing and is a defect.

bm

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"Proper air gap spacing"??? What is that?

IRC E3807.2 Damp or wet locations. In damp or wet locations, cabinets and panelboards of the surface type shall be placed or equipped so as to prevent moisture or water from entering and accumulation within the cabinet, and shall be mounted to provide an airspace not less than 0.25 inch between the enclosure and the wall or other supporting surface. Cabinets installed in wet locations shall be weatherproof.

You are correct, air space should be left open to the air, not filled with sealant. That is why the little bumps are made into the back of the boxes are there, to provide the 1/4 inch air gap.

Originally Posted by brianmiller

For new construction , should the builder NOT seal the service equipment panel and the A/C disconnect boxes to the brick veneer. I'm thinking that the Builder sealing the back of the panel and disconnect boxes to the brick veneer prevents proper air gap spacing and is a defect.

bm

Originally Posted by Speedy Petey

"Proper air gap spacing"??? What is that?

Brian,

You are correct.

That 1/4" spacing is required to allow ventilation behind the enclosure to help keep condensation from forming and to separate the metal enclosure from the wall surface the enclosure is mounted on.

NONE of the gaps around the enclosure are allowed to be sealed.

There is an exception to the above, though, and that is if the enclosure in non-metallic. The reason for the exception is that the non-metallic enclosure is not going to rust, corrode, etc.

Peter, this section:
- 312.2 Damp and Wet Locations.
- - In damp or wet locations, surface-type enclosures within the scope of this article shall be placed or equipped so as to prevent moisture or water from entering and accumulating within the cabinet or cutout box, and shall be mounted so there is at least 6-mm (¼-in.) airspace between the enclosure and the wall or other supporting surface. Enclosures installed in wet locations shall be weatherproof. For enclosures in wet locations, raceways or cables entering above the level of uninsulated live parts shall use fittings listed for wet locations.
- - - Exception: Nonmetallic enclosures shall be permitted to be installed without the airspace on a concrete, masonry, tile, or similar surface.
- - - - FPN: For protection against corrosion, see 300.6.

But at the same time the penetration needs to be sealed. I am not saying the whole enclosure should be sealed though on all four sides.

What would the issue be with sealing 3 of the 4 sides leaving the bottom open?

I think the problem is with the word "air space", the word "air" to be specific. I see now what Brian meant by "air gap spacing".

I understand about the 1/4" requirement, but I also see no "defect" in sealing an enclosure to keep moisture from running behind it. Is that not the specific intent of this section?

Originally Posted by Speedy Petey

But at the same time the penetration needs to be sealed.

Absolutely!

The reason I've been given as to why the various contractors seal around the entire enclosure is to stop leakage, when I tell them they need to seal the penetration they say how, so I tell them "BEFORE the enclosure is installed, seal around the penetration.". They respond that they cannot get anyone to do that, which I remind them is as simple as saying that if the electrician DOES NOT seal around the penetration, his job will not be complete and he will not get his check - and they say "Oh, we can't do that."

Yeah they can, they just don't.

What would the issue be with sealing 3 of the 4 sides leaving the bottom open?

That stops air movement and allows for condensation to build up behind the metal enclosure.

I think the problem is with the word "air space", the word "air" to be specific. I see now what Brian meant by "air gap spacing".

I was at a seminar many years ago where John Minick (you've probably heard of him and the seminars he does, I've been to several) where this issue was discussed at length, explaining that the air space is not there just to separate the two materials (the back of the enclosure and the wall surface) but to allow for air flow behind the enclosure to help keep it dry, helping to prevent condensation, rusting, and corrosion.

I understand about the 1/4" requirement, but I also see no "defect" in sealing an enclosure to keep moisture from running behind it. Is that not the specific intent of this section?

It is the specific intent of that section and it is a defect.

This is the reason that panels have the dimple at the mounting holes. To allow for the air circulation. On a masonry wall moisture will wick through the masonry , thus creating moisture behind these panels. Now if you seal them up how long will it take for the moisture to dry out? Leave the 1/4" air space it drys up quite nicely.

Like speedy and Jerry said the proper way is to seal the penetration only prior to mounting the enclosure.

I did not read Petey to be saying the same thing as Jerry said, he was saying to seal 3 ofr the 4 exterior sides.

Originally Posted by John Goad

I did not read Petey to be saying the same thing as Jerry said, he was saying to seal 3 ofr the 4 exterior sides.

They both state the penetration needs to be sealed. That's what I referred too.