2008 NEC RX connector in cover plate

[STEELER]

Can I install a right angle RX connector in a plastic (PVC) square cover plate mounted on to a plastic box behind a double oven? My customer refuses to allow a hole drilled in the adjacent cabinet so the pigtail can connect to a j box. I only have 3/4" between the rear of the oven and the drywall.
Thanks
Steeler

 

[al hildenbrand]

Can I install a right angle RX connector in a plastic (PVC) square cover plate mounted on to a plastic box behind a double oven?

I'd substitute a 4 square steel cover, drill & tap a ground screw and bond to the EGC. The flat steel would even be a skosh thinner than the PVC flat.

If this is a 2 gang box with device mounts, substitute a stainless steel 2 gang blank cover.

 

[Dennis Alwon]

Can I install a right angle RX connector in a plastic (PVC) square cover plate mounted on to a plastic box behind a double oven? My customer refuses to allow a hole drilled in the adjacent cabinet so the pigtail can connect to a j box. I only have 3/4" between the rear of the oven and the drywall.
Thanks
Steeler

I have been known to cut the back out and the sheetrock and install the box in the wall cavity. I would not trust a plastic plate. Not sure that you need to ground the plate as the cable will ground the plate coming back from the oven.

 

[STEELER]

I'd substitute a 4 square steel cover, drill & tap a ground screw and bond to the EGC. The flat steel would even be a skosh thinner than the PVC flat.

If this is a 2 gang box with device mounts, substitute a stainless steel 2 gang
blank cover.

Yes, it is a 2g box. I think there is a prohibition in the code about drilling a hole in a blank cover plate but I can't find it. I have some blank cover plates with 1/2" KO knockouts but an inspector told me I could not use them. He told me that the EGC would be broken the moment the cover plate is removed. The drill and tap idea violates something in the code but I can't find it. That is the reason for the plastic box and cover.

 

[al hildenbrand]

Yes, it is a 2g box. I think there is a prohibition in the code about drilling a hole in a blank cover plate but I can't find it. I have some blank cover plates with 1/2" KO knockouts but an inspector told me I could not use them. He told me that the EGC would be broken the moment the cover plate is removed. The drill and tap idea violates something in the code but I can't find it. That is the reason for the plastic box and cover.

Use a ground clip instead of a screw. With a bond jumper from the cover plate to the EGC in the NM box the continuity is not broken when unscrewed.

There's even tech art in the NEC Handbook showing a flexible metal raceway extension from the face of a blank single gang cover.

If you don't like the ground clip, get a grounding bushing for the 90 degree connector and bond to the EGC.

The oven flex whip is going to have its own EGC inside it anyway, right?

 

[al hildenbrand]

There's even tech art in the NEC Handbook showing a flexible metal raceway extension from the face of a blank single gang cover.

The NEC Handbook image is Exhibit 314.6 following Code Section 314.22 Exception.

 

[Dennis Alwon]

Al, why do you feel the need to ground the plate with a screw?

 

[al hildenbrand]

Al, why do you feel the need to ground the plate with a screw?

Well, Steeler said this is an oven so I assume the OCPD is at least a 30 Amp. So 250.118(5)(b) is not met. The box is PVC so the cover plate is not bonded to the EGC by the screws.

And, as a bonus, the inspector will be able to see the ground screw stud or ground clip and understand there is a wire attached that will maintain the EGC connection to the coverplate.

 

[al hildenbrand]

Yes, it is a 2g box. I think there is a prohibition in the code about drilling a hole in a blank cover plate but I can't find it.

You won't find it.

I have some blank cover plates with 1/2" KO knockouts but an inspector told me I could not use them. He told me that the EGC would be broken the moment the cover plate is removed.

So you've got a two gang device box blank cover with a factory KO in it and you want to make it larger? Ask the inspector to give the code citation that says you can't do it this way. Show him the Exception to 2008 NEC 314.22

The drill and tap idea violates something in the code but I can't find it.

You won't be able to find that one either.

 

[George Stolz]

Well, Steeler said this is an oven so I assume the OCPD is at least a 30 Amp. So 250.118(5)(b) is not met.

I don't imagine he is using the flex as the EGC for his oven...?

The box is PVC so the cover plate is not bonded to the EGC by the screws.

It is bonded by the metallic connection to the flex which is connected to the metal oven, per 314.22 exception.

I can see you coming with an argument that, therefore, to the cover the FMC is an EGC; I'd say you're probably technically right, but I would take a metal cover bonded in this fashion for mechanical strength over a "safe" drilled plastic cover any day of the week, IMO. It's kind of odd that the bonding would be good enough for the FMC but not good enough for the coverplate that has been punched, when you exceed 20A.

It's late, hope that made some sense.

 

[George Stolz]

...Show him the Exception to 2008 NEC 314.22...

You sure can take the wind of of my sails, my slow typing meant you turned it up first.

 

[al hildenbrand]

I don't imagine he is using the flex as the EGC for his oven...?

Well, I'm saying, without the bond, either to the EGC wire in the FMC or by a jumper to the branch circuit wiring, the metal cover plate "floats".

I know, I know, the FMC is short and metal and really acts as a fair enough wire, but, I think, 250.118(5)(b) says the metal cover plate is essentially on the end of flexible NON metallic conduit.

It is exposed, so it needs the bond, IMO.

 

[GUNNING]

Kiss

Kiss

Open up the wall and use a ko on the new metal 4 square box u installed with connectors. Notch out a trough under the 4 square, connect the flex, blank the box patch and vacum. Its just drywall.

 

[STEELER]

Thanks to all. Problem is solved.

 

[al hildenbrand]

Thanks to all. Problem is solved.

Care to share?