Is wood allowed in a relay box?

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peter

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I intend to install a metal box with some 120 volt relays [5 amp load?]. The problem is how to mount the relays. Is it permissable to mount a piece of plywood in the back of the box to mount the relays on?
Nothing I have read in the Code indicates otherwise and the guy at the distributor says that is the way everybody does it. That is, what is the alternative? I've seen those metal screens, but they don't stock them.
~Peter
 
Re: Is wood allowed in a relay box?

Peter,

Your supplier should have a track that is made just for this installation. You screw the track to the cabinet,then snap the relay bases right to it.

Or the old school way is to drill and tap every hole for #8-32

frank
 
Re: Is wood allowed in a relay box?

To be more precise, this metal box will be mounted on a concrete, tilt-up wall. I've used self-tappers before but that was mounted on drywall so the screw tips sticking out the back didn't matter.
 
Re: Is wood allowed in a relay box?

I've done this before with self-tapping screws but that box was mounted on drywall so the points sticking out the back didn't matter. But this box will be mounted on a concrete wall.
My wuestion is whether there is some specific Code article which prohibits the use of plywood in a little relay box.
We are not sophisticated enound to use DIN rails.
 
Re: Is wood allowed in a relay box?

Why not? DIN rail is cheap. Phoenix blocks with Idec relays are realy cool. You can mount Panduit on both sides of the DIN rail to manage the wires. Not too expensive and very clean looking.
 
Re: Is wood allowed in a relay box?

I just have to ask this. Is it ok to have a relay in a wood box?. If not please let me know, as I have several stored away in a wooden box.
 
Re: Is wood allowed in a relay box?

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Your wood inside should be fine. There are manufacturers that make boxes specifically for what you're doing. Take a look at this:

http://www.hoffmanonline.com/iHelps/Product.cfm?ID=7010A


If this does not work than I would suggest using self drilling screws and grinding the back part of the screw off that penetrates the back of the box. Self tapping screws as mentioned would require you to drill a pilot hole for each screw.
 
Re: Is wood allowed in a relay box?

Originally posted by infinity:
Your wood inside should be fine.
Click to expand...
I disagree, IMO the construction must be out of metal or listed for the use.

312.10 Material.
Cabinets, cutout boxes, and meter socket enclosures shall comply with 312.10(A) through (C).

(C) Nonmetallic Cabinets. Nonmetallic cabinets shall be listed or they shall be submitted for approval prior to installation.
Click to expand...
IMO this applies to the exterior and interior of the box.
 
Re: Is wood allowed in a relay box?

Originally posted by macmikeman:
I just have to ask this. Is it ok to have a relay in a wood box?. If not please let me know, as I have several stored away in a wooden box.
Click to expand...
No, you need to transfer the relays that are in the wood box into a plastic or metal box, such as a surplus ammo can or a milk crate. :)

I'm with Bob on this one.
 
Re: Is wood allowed in a relay box?

Like Bob has mentioned, there may be an issue with the listing of the enclosure. It may simply boil down to the fact that the wood has not been tested in the enclosure and that could be an issue.

Yes we have all probably installed wood blocks in enclosures as " I did this many times" echoes in my ears... that does not necessarily make it correct.

The din rail really is the way - it will not take any longer than installing the wood, and you look like a professional - just what we are trying to do ;)

That is what separates us from the " bees leaving the big box stores"!!!!!!!!!!!
 
Re: Is wood allowed in a relay box?

if you cannot find din rail close to you.
you can install a raised bottom in the encloser,like a nema 3 combination starter disconnect or any nema 3 control box.
 
Re: Is wood allowed in a relay box?

I don't believe installing a wood panel in a box voids it's listing, as it is not part of the box. (does UL say no wood can be installed inside)

My preference would not be to use wood. If you do, how about using fire resistant plywood? Quite common for communication equipment mounting.

Or mount the panel on unistrut, so the self-tappers will not hit the concrete panel.
 
Re: Is wood allowed in a relay box?

Another variation:

Put the plywood on the concrete. Then mount the panel to the plywood. Mount relays with self tappers.
 
Re: Is wood allowed in a relay box?

I'm curious about what type of box you are planning on using. If it's a typical j-box, isn't it also designed to accept a panel for the purpose of mounting components and hardware? The panel allows space for the screws so you don't have to penetrate the back of the box and derate its construction, if that's an issue.

I don't think I like the idea of using wood inside an electrical enclosure. Seems like a fire hazard waiting to happen. Never heard of fire resistant wood. Is there such a material?

Could you use a different material such as a type of plastic or nylon? It would be less prone to deterioration from moisture, insects, or time. Of course, now it would be less costly to just buy a short section of DIN rail.

Bob
 
Re: Is wood allowed in a relay box?

I don't see how a wood panel would violate the UL listing in a small box as there is typically nothing stated in the instructions prohibiting such an installation.

In larger boxes, it is often stated that a specific metal sub-panel should be used.

If the box is part of a machine this would be prohibited as a metal sub-panel is a requirement of NFPA79.

Best bet is to buy some din rail mounted relays.

Mount the box off the wall 1/2 inch or so so the screws holding the din rail in place have somewhere to go. Or just grind them off.
 
Re: Is wood allowed in a relay box?

try using solid wire then just let the conductors hold the equipment in place..
 
Re: Is wood allowed in a relay box?

I disagree, IMO the construction must be out of metal or listed for the use.


quote:
--------------------------------------------------------------------------------
312.10 Material.
Cabinets, cutout boxes, and meter socket enclosures shall comply with 312.10(A) through (C).

(C) Nonmetallic Cabinets. Nonmetallic cabinets shall be listed or they shall be submitted for approval prior to installation.
--------------------------------------------------------------------------------

IMO this applies to the exterior and interior of the box.
Click to expand...
I still say that a metallic enclosure with wood on the inside is OK. 310.12(C) is for non-metallic cabinets. I'm saying that the wood would be OK inside of a metal cabinet as proposed in the original post.
 
Re: Is wood allowed in a relay box?

The box in question is a metal gray Hoffman box, 6" by 6" by 4". I fitted a piece of plywood in it with 3/4" lath screws inserted from the back. I mounted two Siemans DPDT 30 AMP, 120 VAC relays on it. [3TX7130--ODF13]
The article mentioned [312.??] is actually 373-10 since California code is used [1999] here in San Diego. But it says the same and I feel it refers to the material used in its manufacture, not the contents. [It cost me $7.98.]
We use the words "switchboard" and "panelboard". So what are boards made from? Wood is more or less non-conductive. The only problem is combustability but I dont think a piece of 4" by 5 1/4" piece of 1/2" ply is much of a fuel load.
~Peter
 
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