Article 312

[Terry Bruton]

Hello Everyone (my first post on the forum)

I tried to first do a search but wasn't successful - so here's my question:
Specially 312.2, that requires a minimum of 1/4" airspace between enclosures and the wall or supporting surface, I'm interpretting this as the "finished" wall or surface and not embedded into stucco. Some electricians wait for the finished wall and others want to do a "scratch coat" of lesser thinkness than finished stucco and then the finished stucco will be right up against the enclosure - looks pretty but stucco can crack and thus allow water behind the enclosure and maybe into the building. I appreciate any and all opinions.

Thank you, Terry Bruton

 

[AK GUY]

The intent of the code is pretty clear. IMO wait for the final coat, but little you can do especialy if the General wants the equipment installed, after that it's his respossability.

 

[Dennis Alwon]

I agree with AKguy. Most equipment come with a 1/4" raise in the back so that must be mounted on the finished wall.

 

[Jon456]

looks pretty but stucco can crack and thus allow water behind the enclosure and maybe into the building.

Hi Terry, welcome to the forums.
The way I read it, the code is not concerned about water intrusion into the building, but rather water intrusion into the enclosure.

312.2 Damp and Wet Locations. In damp or wet locations, surface-type enclosures within the scope of this articleshall 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 (1⁄4-in.) airspace between the enclosure and the wall or other supporting surface.​

I think it's pretty clear that the 1/4" applies to the finished wall. Otherwise, it wouldn't be an "airspace".

But note that there is an exception:

Exception: Nonmetallic enclosures shall be permitted to be installed without the airspace on a concrete, masonry, tile, or similar surface.​

 

[renosteinke]

This is a "find" that is currently making the rounds of the HI forums. Why, they say, the code forbids you to 'recess' an outdoor rated panel into the face of the building, even a little.

I don't see it that way, but it's difficult to explain that outside moisture can't rot away the back of the box if the back of the box is out of the weather completely.

I'd like to see some discussion of this point. I have an upcoming service change where the house siding is cement tiles - quite brittle, and far from 'flat.' I'd prefer to cut them away from the wall, and mount the panel directly to sheathing. (BTW, the wires will exit the back of the panel). After all, I've yet to drill & attach to these brittle older tiles without something cracking ... and the lap of the tiles intrudes on the drainage space in any event. Let me flash around the panel, though, and the wall is protected.

So, the question is: MUST an outdoor panel be mounted completely above the finished face of a building?

 

[Hv&Lv]

How many times have you seen a meter base mounted to a wall before the vinyl siding is installed?
Maybe a case for the NEC revision team?

 

[Terry Bruton]

Thank you all for the replies - and it's a pleasure to be on this forum.

I've talked with several people in the trade and outside the trade in the past, and with the feedback I'm getting here, it seems that most are in agreement that it's clear in 312.2 that meter, cabinets and cutout boxes are intened to be mounted to the wall or other supporting surface. I think maybe there should be a couple illustratons in the NEC handbook or a couple sentences added to help clarify - it's clear to most, while not to others.

I've mounted equipment on the surface of vinyl siding and hardy board siding, etc with no problem. I understand that Arlington makes a backing for use on vinyl siding where it can all be locked together somehow.

As to that fragile tile siding, possibly a backing of some sort could be installed and then the equipment installed on that - no leaks, meets 312.2, no broken tiles and everyone is happy.

This topic will be brought up at our monthly IAEI-Treasure Coast meeting this Wed, Aug 10th 4-6 pm at the City of Port St Luce Building Dept, and we always have our doors open to anyone who wants to attend.

Thanks again, maybe more people will chime in, the more the merrier.
Terry Bruton

 

[Jon456]

I don't see it that way, but it's difficult to explain that outside moisture can't rot away the back of the box if the back of the box is out of the weather completely.

Because it's impossible to get a long-lasting water-tight seal between the outside wall surfacing material and the sides of the enclosure. Remember that the service-life of such panels are measured in decades. With thermal expansion/contraction, house settling and movement, and the affects of aging and weathering, I can guarantee that whatever seam you make, no matter how well-sealed at time of installation, will eventually leak water to the back of the enclosure. Once inside, the moisture cannot freely evaporate (that's the purpose of the required airspace) so it will begin to corrode the back of the steel panel.

I have an upcoming service change where the house siding is cement tiles - quite brittle, and far from 'flat.' I'd prefer to cut them away from the wall, and mount the panel directly to sheathing. (BTW, the wires will exit the back of the panel). After all, I've yet to drill & attach to these brittle older tiles without something cracking ... and the lap of the tiles intrudes on the drainage space in any event.

I can think of at least four ways to accomplish this and meet the requirements of the code:

Method 1: Obtain a sheet of building material of your choice that offers a superior mounting surface for your enclosure. Cut it to the outside dimensions of your panel and install it so it flush with the finished surface of your wall. Flash it and seal it as necessary to protect the wall from water incursion. Now you have a perfect mounting "pad" for your enclosure (with the required 1/4" airspace between the panel and your mounting pad).

Method 2: If you really prefer to have the enclosure recessed, you may still do that, but the opening for the enclosure must be at least 1/4" larger all the way around the perimeter of your panel. In other words, the recess opening must be equal to or greater than (W+1/2") x (H+1/2"), where W and H are the width and height of your enclosure. Personally, I would make it (W+1") x (H+1"), thus leaving a 1/2" side gap around the perimeter. Prep and seal the opening as necessary to prevent water incursion into the wall. Now when you mount the enclosure, you still meet the NEC requirement of "at least 1/4" airspace between the enclosure and the wall" (as long as you don't try to fill the airspace on the sides with some type of sealer). Note, the NEC does NOT specify that the airspace applies only to the back of the enclosure, so this is code-compliant (and it makes sense: the airspace all the way around the sides and behind the panel allow for any moisture to evaporate freely).

Method 3: Use a non-metallic enclosure as stipulated in the exception to 312.2.

Method 4: Build a utility closet or other enclosure on the side of the house so that your electrical panel is no longer in a "damp and wet location".

Let me flash around the panel, though, and the wall is protected.

As I pointed out in my earlier post, the NEC is not concerned with protecting the wall; it is concerned with protecting the enclosure.

So, the question is: MUST an outdoor panel be mounted completely above the finished face of a building?

No. But if the surface-type enclosure is to be mounted in a damp or wet location, then you MUST provide "at least 6-mm (1/4") airspace between the enclosure and the wall or other supporting surface", unless you can apply the exception. I don't see how the code could be any more clear on this requirement.

 

[Jon456]

How many times have you seen a meter base mounted to a wall before the vinyl siding is installed?
Maybe a case for the NEC revision team?

The problem is not the NEC, nor the intent of the code. The problem is lack of knowledge and poor compliance, both by the installers and the inspectors.

 

[Terry Bruton]

The problem is not the NEC, nor the intent of the code. The problem is lack of knowledge and poor compliance, both by the installers and the inspectors.

I agree whole heartedly

 

[texie]

Terry,
I'm originally from Dade county and I recall this become a hot button issue back in the '80's. Our then Chief was a tough but fair guy and well versed in all things NEC. His ruling was must it be on the finished surface. Far as I know they still enforce it. IMO this is correct.
By the way, I have a nephew that is a GC in your neck of the woods.

 

[Terry Bruton]

Terry,
I'm originally from Dade county and I recall this become a hot button issue back in the '80's. Our then Chief was a tough but fair guy and well versed in all things NEC. His ruling was must it be on the finished surface. Far as I know they still enforce it. IMO this is correct.
By the way, I have a nephew that is a GC in your neck of the woods.

I moved from Broward County to Port St Lucie in May 1989 - I am so glad my early training was in Broward - lots of people here that used to live down south, in all walks of life (might even know your nephew). I was told one time about mounting service equipment, etc on the finished surface and it stuck with me ever since, think that was the mid 70's, however, best I can remember I and the others I worked for previously always waited for the finished surface before mounting equipment - apparently others were too for there to be a code change on it.

 

[renosteinke]

I want to thanks all for their thoughts!

Just some random thoughts on some of the solutions ...

So the drainage is only needed in 'wet' locations? When you bury the back of the box in the wall, are you not removing it from the 'wet' location?

Drainage space all around the panel? An interesting thought, one that goes hand-in-hand with properly flashing around the opening one might make in the siding. Once you do that, then the flashed area would become the finished surface, wouldn't it?

Building a 'doghouse' around the panel is an interesting solution, which I believe has been the subject of lively debate in the past. Something about working space and clear space, IIRC. Indeed, those issues might arise for even slightly recessing the panel into the siding.

Backing panels ... now, there's a concept. I think my neighbor has one made of sheet metal; I'll go look. Otherwise, I'd have to reject the traditional painted plywood as wholly unsuitable. I've seen far too many weather poorly- which is a pity, as the plywood can often solve a lot of support problems.

Bushings or stand-offs? There's a thought. One could possibly use the 'double ended screws' (one end lag, the other machine threads) we use to hang stuff from ceilings.

Those brittle tiles .... the vinyl siding .... yup, I think the NEC needs to recognize some of the real-world circumstances that arise. I think there's room for some editing next time around.

 

[readydave8]

in regards to backing panels, I did a service recently where I screwed pt plywood to studs and covered it with FRP, plan to use J mold for the siding around perimeter of backing--if I remember I'll check it in 20 years to see how well it works.

 

[Chamuit]

We use Backpans. I have even cut out stucco, mounted a couple of sheets of plywood (for stability) set the backpan on, and caulked it in. The backpans maintain the airspace behind and around the enclosure.

 

[Jon456]

So the drainage is only needed in 'wet' locations? When you bury the back of the box in the wall, are you not removing it from the 'wet' location?

No, now you're trying to play with semantics. The code applies to the entire enclosure, not just the back side of the enclosure. So unless you are burying the entire panel under a layer of stucco, you still have to meet the requirement.

Drainage space all around the panel? An interesting thought, one that goes hand-in-hand with properly flashing around the opening one might make in the siding. Once you do that, then the flashed area would become the finished surface, wouldn't it?

Yes. And there still must be a minimum 1/4" airspace (not "drainage space") between the enclosure (on all sides) and the finished surface, whether that surface be stucco, vinyl siding, tile, brick, concrete, wood, flashing, or straw thatch.

Building a 'doghouse' around the panel is an interesting solution, which I believe has been the subject of lively debate in the past. Something about working space and clear space, IIRC. Indeed, those issues might arise for even slightly recessing the panel into the siding.

I'm not sure why the debate would be so lively, as the code is pretty clear on the space requirements. Comply with the code and there are no issues. It's not uncommon to see cabinets constructed around service entrance panels on multi-family dwellings. I doubt a "slight recessing" would trigger a working space violation. But in any case, I never said that the panel itself needed to be recessed. I said a 1/4" recess could be made in the finished wall behind the panel to allow for the required airspace (keeping in mind that the recess would have to be wider and taller by at least 1/4" all the way around the panel). Once the panel is mounted with the required 1/4" standoff, the back of the panel would be "flush" with the rest of the finished wall.

Those brittle tiles .... the vinyl siding .... yup, I think the NEC needs to recognize some of the real-world circumstances that arise. I think there's room for some editing next time around.

The NEC requirement is there for a reason: to prevent water from accumulating behind the panel and corroding it, which would result in a hazardous situation. The airspace allows water to drain away and any moisture to evaporate. Changing the code to make it "comply" with incorrect "real-world" installation methods will not change the real-world physics that lead to panel corrosion. Mother nature does not care how challenging it is to mount the enclosure.