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Old 01-06-2013, 08:19 PM   #1
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Metal covers plastic boxes


I was doing a lot of low voltage wiring above a drop ceiling the past few weeks and noticed there were several electrical boxes that had no covers, some had wires sticking out that were live, and some had metal covers while the boxes themselves were plastic.

I removed the excess wires that were sticking out out of several and would like to close the boxes up since I'm sure code doesn't allow for these boxes to just be open to the area above a drop ceiling.

The problem I'm having is that the only covers I'm finding that fit are metal 3.5" round covers. The plastic covers all seem to be for a 4" round box. I looked around online and didn't see any smaller covers so I'm not holding out a lot of hope for a local electrical supply. The boxes were all used at one point for your basic porcelain light before the basement was finished.

Am I correct that I shouldn't be using the metal covers? Anyone have a source for these smaller covers in plastic or should I plan on replacing the few ceiling boxes?

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Old 01-06-2013, 08:24 PM   #2
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Metal covers plastic boxes


You certainly can use metal or platic covers on plastic boxes. You need to make sure all wires are capped in the box....and you should not mix low voltage wires with line voltage in the same box.

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Old 01-06-2013, 08:26 PM   #3
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Metal covers plastic boxes


There is no problum using metal covers, and yes they should have been covered in the first place.
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Old 01-06-2013, 08:43 PM   #4
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You certainly can use metal or platic covers on plastic boxes. You need to make sure all wires are capped in the box....and you should not mix low voltage wires with line voltage in the same box.
They are indeed all capped off now that I removed the pigtails that went to the old lights that no longer exist. Yeah I learned the no mixing low and line voltage wires earlier when doing some networking.

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There is no problum using metal covers, and yes they should have been covered in the first place.
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Old 01-06-2013, 08:46 PM   #5
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Metal covers plastic boxes


You cannot use metal covers on plastic boxes unless the cover is bonded in some fashion. Some of the round plastic boxes will have a ground screw connected to a metal sleeve for one of the screw mounting holes for this reason. They do make round plastic covers.
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Old 01-06-2013, 08:47 PM   #6
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Metal covers plastic boxes


That link is to a 4" cover that does not work on my boxes. I know because I have 3 coasters in my basement.

edit: The bonding comment is exactly why I was asking. As I see it with these covers there is no way a screw holding the cover on bonds the box as there is no ground screw in this box.
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Old 01-06-2013, 08:50 PM   #7
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Metal covers plastic boxes


Why, they sell metal outlet and switch covers, what's the differance?
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Old 01-06-2013, 08:56 PM   #8
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Metal covers plastic boxes


I'm going to guess that when you attach a ground wire to a switch or outlet the face plate becomes grounded as well.
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Old 01-06-2013, 09:18 PM   #9
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Metal covers plastic boxes


I don't know if I've ever seen anything but a 4" round plastic box. Worst case, drill some holes in the 4" cover that will line up with the smaller box.

And you are correct, the plate screw will bond a metal faceplate.
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Old 01-06-2013, 10:12 PM   #10
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Metal covers plastic boxes


A ground clip can be used to bond the metal cover to the EGC.
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Old 01-06-2013, 10:25 PM   #11
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Metal covers plastic boxes


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Originally Posted by joecaption View Post
There is no problum using metal covers, and yes they should have been covered in the first place.
The potential problem is that if anything goes wrong inside the box and something is loose, the metal cover can become energized.

If a metal box or cover is used, it has to be grounded. If there isn't a ground or you don't want to do it, then don't use a metal cover. It's easier to ground a metal box because there's a screw hole in boxes to attach a ground screw to.
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Old 01-06-2013, 10:28 PM   #12
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Metal covers plastic boxes


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Why, they sell metal outlet and switch covers, what's the differance?
A metal cover is usually used with a metal box. A metal outlet or switch cover can be used with a plastic if the outlet/switch is properly grounded, because the cover screw threads into the metal outlet/switch frame.
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Old 01-06-2013, 11:55 PM   #13
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Metal covers plastic boxes


Thanks guys. Here is a shot based on what k_buz suggested. It doesn't look the greatest but it works.

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Old 01-07-2013, 12:11 AM   #14
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Metal covers plastic boxes


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Originally Posted by info2x View Post
Thanks guys. Here is a shot based on what k_buz suggested. It doesn't look the greatest but it works.
Good job.

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