Panelboard Mounting on Gypsum - Allowed? 2

I think it will be entirely up to the local inspector - or maybe that's you?

It's done with old work outlet boxes all the time, but I would not be comfortable doing this for a panelboard. Is this is 20" panelboard or a smaller residential loadcenter?

I would want the box supported by the structural members in the wall. I'm not sure I see how the blocks of wood are helping much.

There must be a story behind this.

David Castor

This appears to be poorly addressed in NEC. Article 110.12 does require "neat and workmanlike manner" and FPN refers to
ANSI/NECA 1-2006 and other ANSI-approved installation standards. Now that is as clear as mud.

But almost universal practice in the USA is to attach a fire rated plywood on the gyp board and then screw the panelboard on them. I would think anything less than that (barring recessed installation) would be considered un-workmanlike!

Rafiq Bulsara

We require steel channels (Unistrut) to support the panels' weight.

No known code requirement - just good practice.

There are NECA Installation Standards that might be of some help for moral persuasion. I don't have a copy here so I can't tell you how well this might be addressed.


David Castor

Studs are 16" on center right? Why can't they mount it on the studs?

Unfortunately I am not located at our field office in DE but I have requested photos so I can see how the wood blocks are reinforcing for structural support. I will also know more of the story as to why they are not using structural framing such as studs or even unistrut for support once I get a hold of our field office. Our specifications have recently been updated and previously there was a line stating not to use gyp board walls for support but somehow it was removed (we just found this out now).

We are most likely going to state it is not Good Workmanship but would like something more solid such as a standard. The project is new construction so there is no reason not to have structural framing for support.

I do not have access to NECA 1 either. I believe the CTR is not hitting studs because in a couple cases we have 2 or 3 panels mounted next to each other and before the gyp board went up the CTR must not have installed horizontal bracing. Using 4 toggle bolts to hold up a 200+ panel is definitely not good workmanship.

Studs are sometimes 24" on center, which sounds like it is in this case (I could be wrong). In any case I would consider toggle bolts poor workmanship. I would at least build a support structure out of 2X4's around the hole for the panel (I'm assuming this is recessed).

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If it is broken, fix it. If it isn't broken, I'll soon fix that.

Panel Boards are "listed". I am prettysure the instructions for GE and SquareD had instructions for installation. I am pretty sure there were no molly bolts in there.

If this is any kind of normal construction, there's something behind that gypsum wall board that can be used to support something like the unistrut, plywood or even just some 1X lumber to fasten the panels to.

The fact that they have the wood blocks in between already shows that they know it is not sound and also means there's no problem with it being shimmed out from the gypsum by the distance necessary for some structure beind it.

The studs are 16" on center and the panels are surface mounted. Basically the contractor has the panels surface mounted to the wall and the toggle bolts then go thru the panel, thru the drywall and thru the wood blocking. The wood blocking is basically a 1"x4" and about 6" long and they did not insert the blocks at every location.

Pics: (copy and paste into your browser if necessary)


The manufacturer installation instructions that come prepackaged with the panels refers to standards for installation such as the NEC and PB1.1. This is the case for Siemens panels. I am not sure about other manufacturers.

Thank you "ccjersey." You make a very good point that if the contractor is placing wood blocks in for support then the contractor must know that drywall is not the best support. Either that or they cracked enough drywall when inserting the toggle bolts they needed extra support. The second picture above shows a toggle bolt basically ready to fall out of the wall.

Our specs also call for surface mounted enclosures to have a 1/2" gap between the wall and the contractor is violating this also. This would be a great place to have unistrut installed. This would add structure and support and fulfill our requirement.

It looks like I am going to have to pursue "Good Workmanship" and the 1/2" gap standard we require to get this installation in order.

The single toggle bolt appears to have been driven through the wall rather than being installed in a pre drilled hole. Another instance of overall poor workmanship.
BUT, with metal studs I would suggest that as well as being bolted to the studs, backing strips be installed between the studs.

Bill
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"Why not the best?"
Jimmy Carter

You can look at this document for some information on using toggles to support things on a drywall surface.

In Article 110.12 it states equipment shall be installed in a neat and workmanlike manner. The FPN refers to NECA 1-2006 as an accepted industry practice but the FPNs are for information only.

NECA 1 states:

Section 10. Equipment Mounting
"a) The fasteners or supports shall be sufficient to substantially secure the equipment in place to the building structure or structural element."

Gypsum board is not a structural element (merely aesthetic) therefore should not be used as a support for equipment. Unfortunately our specifications do not reference this standard. In the end, the AHJ has the authority to make interpretations of the rules listed in the NEC and the neat and workmanlike manner sits under this approval.

We have come to an agreement with the contractor to provide unistrut framing behind the panels but I will be sure to add this standard to our specifications and plans.

Thanks again to everybody.

axm:
Thank you for the feedback and I am glad that an amicable solution worked out for you.

Rafiq Bulsara