Stupid sub-panel question

[Mike Ruggeri]

I am in the process of putting in a sub-panel in my attached garage. Is it OK to mount the panel directly to a concrete block wall? I keep seeing pictures of panels mounted to a piece of plywood that is then attached to the wall. I much rather mount it directly to the block as all the wires going in and out will be in conduit and I just don't see a need for the wood between. Am I missing something?

Thanks and apologize if this is a really dumb question.

Mike

[Philip Rodriquez]

no problems. Just make sure you use the correct fastners.

[Rick Moyer]

No electrician here, but I believe the reason is moisture between the panel and the wall. The ply acts as a barrier.

[Rollie Meyers]

Moisture & wood do not go together well, if it's too wet to mount a panel direct to concrete, it's too wet for plywood, if that was the case 1/4" standoffs behind the panel should take care of the issue if that is the case.

[Jason Roehl]

My main panel is in my garage, mounted directly to the CMU block wall. When the home inspector was here before we bought, he said this violates current code, but he also said that if the block is staying dry, and there's no indication of rust on the panel to not worry about fixing it. Otherwise, plywood is required. I don't think standoffs are kosher, either, as it creates a space for vermin and other debris to accumulate, which is then a fire hazard.

[Mike Ruggeri]

If it matters, the wall is dry. If I need ply behind the panel then what thickness does it need to be?

Thanks

Mike

[Rob Russell]

This is one of those things when it's best to ask the local AHJ (Authority Having Jurisdiction, aka the building inspector) what they want to see. If you're putting in a subpanel I'm assuming that you've pulled a permit and will have it inspected, so just ask the AHJ how they expect the panelboard to be mounted.

[Dave Wagner]

Yes, check local/national codes.

Maybe paint some DryLok behind it as a moisture barrier (if you don't use a piece of plywood) and put a couple washers between the box and wall to give it a small air gap so there is no moisture trapped between the box and wall and there is some air flow behind the box.

[Rod Sheridan]

Home panels are often mounted on fire retardant plywood so that the romex can be stapled to it.

That will be an issue with mounting it on concrete directly, unless you use EMT or BX.

As others have correctly indicated, check with the local authority.

Regards, Rod.

[Anthony Scira]

You can get fancy and put it on some unistrut. I have run a lot of conduit and set a lot of panels in parking structures and electrical rooms. Most are right to the concrete.

Using the 7/8 strut for the panel and 1 5/8 for the conduit saves having to make the offsets.

But yeah ask your inspector. And if you have to use plywood it will have to be fire rated. And make SURE you have the factory stamp of the fire rating VISIBLE. Don't ask how I know ;)

That inspector was a JERK !