Plywood backplate inside 480 volt load center?

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cliffer1

New member
Has anyone come across a load center cabinet with the breakers, contactor, etc. mounted to a plywood panel inside? I have seen it with low voltage lights but never 480 volts.
Can you point me to an NEC reference for this being acceptable?
The load center controls roadway lighting for D.O.T. street lights and high-mast towers.
Thanks!
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Has anyone come across a load center cabinet with the breakers, contactor, etc. mounted to a plywood panel inside? I have seen it with low voltage lights but never 480 volts.
Can you point me to an NEC reference for this being acceptable?
The load center controls roadway lighting for D.O.T. street lights and high-mast towers.
Thanks!

I don't know the code reference, or if something like this is even within the code's jurisdiction, but I have seen it in the field.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
DOT can pretty much do as they please. Governmental agencies are usually exempt from the pesky rules that apply to the rest of us.

My guess is that there is no rule on what these backplanes are made of to be found in the code.
 

mgookin

Senior Member
Location
Fort Myers, FL
In Florida a unit of state, county or city government does have to comply with code.

However, highways, bridges and things accessory thereto are exempt, and that exemption does include traffic signals and highway lighting.

OP needs to find out if job specs or the FDOT construction manual compel compliance with the NEC because statutorily it does not.
 

big john

Senior Member
Location
Portland, ME
Only thing I know that comes close is the restriction on setting switchboards on wooden floors.

Maybe the distinction here is that while a wooden backboard would burn, it still wouldn't permit flame-spread outside the enclosure.
 
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