Do main panels have to be mounted on a piece of plywood? Can it be mounted in between two studs then insulating fiberglass behind it?

  • 4
    What is your AHJ? Are you in the US, Canada, the UK ...? – K.A.Monica Jan 6 '14 at 21:47

If in the US, the language is more general; fundamentally, the panel must be solidly supported, and not prone to fall off the wall as time passes. I personally prefer to have 5/8" type X drywall over the actual support when using a wooden support, for additional fire resistance. It's not required, but as the comments imply, your local "Authority Having Jurisdiction" (AHJ) is what really matters. That is your local electrical or building inspector; however, you can exceed their requirements so long as you actually meet them. That is where I'd class my affectation for firecode drywall on top of wood .vs. exposed wood.

The wall can be insulated, but the service entrance wire should pass though as directly as possible, and preferably in conduit.

From 2011 NEC:

110.13 Mounting and Cooling of Equipment.

(A) Mounting. Electrical equipment shall be firmly secured to the surface on which it is mounted. Wooden plugs driven into holes in masonry, concrete, plaster, or similar materials shall not be used.

Having met a few things mounted this way, I can attest that wooden plugs in masonry rot, shrink, or both and do come loose, thus the specific exclusion.

Incidently, many panels can be mounted in the wall cavity between studs, though that can complicate the actual wiring in some ways. Perhaps that was what you were asking in the second question - it seemed like you were asking if a plywood mount could be placed that way. If it is your question, the answer is "Yes, if the box is designed for it and the wiring can be run in the space then available." It will reduce your wall insulation at that spot considerably. Many boxes will still need a solid support behind them, between the studs, to accommodate their mounting screw hole placement.

| improve this answer | |
  • Thank you for your comment.I have mounted the panel thru the sides with existing holes and some that we're there already.but do I hae to have something on the back of the panel.I thought of putting metal tape to cover the holes in the back of it then fire proof foam it or fiberglass it for insulation. thanks perry – Perry Jan 7 '14 at 16:04
  • This is right behind the front door of a new addition.That's why I don't flush mount it. – Perry Jan 7 '14 at 16:07
  • If the box has mounting holes to the side, none to the back are needed. You ARE flush mounting; what you are avoiding due to location is surface mounting. I don't know if behind a door meets the requirement for "clear space around the panel" or not; that might be an issue. – Ecnerwal Jan 7 '14 at 16:18
  • Some of the information in this answer might also be useful. – Tester101 Jan 8 '14 at 11:16
  • The panel should be mounted according to the manufacturers instructions (110.3(B)). A copy of the instructions should be provided to the AHJ if they question the installation. – Tester101 Jan 8 '14 at 11:21

In the UK, modern "consumer units" do not need to be mounted on a board. In most UK houses that means they are directly fixed to the inside of an external wall that in most cases is a plastered surface over construction blocks or brick.

You can get flush mount consumer units that are installed into the wall itself.

In previous centuries I believe it was normal to mount fuseboxes on a wooden board. There's probably still a lot of houses with that arrangement.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.