another panel question

Here is another panels question.
Are you allowed to drill hole(s) in the NEMA 12 rated enclosures? Will it compromise NEMA 12 rating and UL listing of the panel? We are drilling holes for 4-40 screws to attach nameplates outside of enclosures and seal these holes with the screws using silicon sealant. Is anybody can point me to the governing instructions?
Thank you.
PaulB.

I wouldn't--but that's just me.

Since you have silicone, why not adhere the nameplates using a thin bead of silicone? Use masking tape to hold the plate in place until the silicone cures.

The NEMA 12 may not NOW be in an area where having the screws installed would allow water in--but what about later. Besides, someone specced a watertight enclosure, why not give them one?

If all you are doing is attaching nameplates, I would recommend an alternative. Instead using screws to attach the nameplates and sealing the holes with RTV silicone, simply use the same RTV silicone to attach the nameplates. NEMA 12 is not all that difficult to meet, but why put extra holes in the panel skin if you don't have to?

The Answer to your question is somewhat complex. Yes you can drill holes in the panel as long as you install fittings that have a nema rating the same or greater than the panel you are putting them into. Installing a nameplate with holes will de-rate the panel rating to a nema type 1 enclosure even if you are using silicon. I would say that a UL inspector will not like a nameplate that is screwed into the panel since (I am you are making the nameplate) there is no NEMA rating on the nameplate. We are a UL listed panel shop and to avoid any problems with the ratings of the panel we epoxy our nameplates to the door. This all comes from UL508.

General Electric had me involved in several big nameplate projects in 1995. No more holes, screws, or metal nameplates. Use adhesive decals. I don't know how far this has gone since, as I have seen the same product lines with both methods.

Since I am not the Six Sigma expert, but if GE was looking into it as a cost out project, then I would say that is the way to go.

I still see a lot of panels with the old engraved plastic (badge type) nameplates held on with double sided tape.

regards all.....casey

What stooper said is correct. Also, don't think you can guess which fittings are the "same or greater than the panel rating". There is a table in the UL508 specification which lists enclosure type and fitting type compatabilities.

However, there is a difference between a UL 508 listed industial control panel and a panel containing UL listed and recognized parts. The first requires either a UL approved panel shop to built it or an expensive one time investigation by UL. Usually you only do this if the end user has a requirement for it. Also, some UL shops will standardize on listing all panels unless there is a component preventing the listing or making it difficut.

Hey stooper, what do you do when you need an air conditioner in a listed panel?

Norm:

See, that UL class does come in handy from time to time.

regards.....casey