Load Center Material Use

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I have a contractor that wants to use a plywood back plate in a NEMA 4R cabinet. He wants to put the plywood panel in, then take all of the guts out of a panel board and mount them to the plywood. I would think that this would violate 408.50 in the 2005 NEC (ie: combustible material), not to mention just asking for problems in a year or two when the plywood decays.
This is in a NEMA type 4 cabinet, pad mounted, 480volt, 300 amp service. This service feeds 12 branch circuits protected by 40 amp circuit breakers, uses a contactor activated by a photo cell, step down transformer to feed 120 volt for contactor coil and photo cell. This load center will control the high mast lights on the interstate. This load center controls 20 poles/80,000 watts and is one of thirteen load centers that would all have the plywood backs. Is there anything that would support my requiring that the contractor use a metal backplate and not the plywood? 408.50 refers to panels of switchboards, would this be considered a switchboard? Due to the late time frame that I have, I don't have a lot of time before this decision has to be made. Thanks in advance for all replies.

 

[Buck Parrish]

The equipment must be UL listed for and used as it was designed.

 

[bhsrnd]

I agree that the UL listing would be violated but equally confused why the contractor would do this. If this were an empty NEMA 4 cabinet for use with mounting control compontents or low voltage type items I could see how this may make some sense. Removing the buss bars and everything else then re-mounting them to plywood makes no sense to me.

I think you would also get into Article 250 violations of grounding and bonding.

Also, I could just be completely misunderstanding what's going on here too. I'm sure I will learn something.