Nonmetallic boxes with metallic switch plates?

[SDRaider75]

I am student at a technical college. We were doing a project in the lab using electrical nonmetallic tubing and nonmetallic double gang boxes. The question came up as to why we could not use metal switch rings on nonmetallic boxes and I could not seem to find where specifically stated this in the 2011Nec codebook

 

[user 100]

I am student at a technical college. We were doing a project in the lab using electrical nonmetallic tubing and nonmetallic double gang boxes. The question came up as to why we could not use metal switch rings on nonmetallic boxes and I could not seem to find where specifically stated this in the 2011Nec codebook

Egc needs to be pulled and connected to switch egc terminal: egc connects to ground screw on switch yoke, metal switch plate is screwed to metal switch yoke and is now bonded (grounded).

See 404.9(B) Provisions for General use snap switches

.......Shall provide a means for metal faceplates to connect to the equipment grounding conductor whether or not a metal faceplate is installed."

Think its the same in the 2011.

 

[infinity]

I don't believe that the question is about metal switch plates but is about metal mud rings on non-metallic boxes.

 

[user 100]

I don't believe that the question is about metal switch plates but is about metal mud rings on non-metallic boxes.

I caught that part about the rings after edit limit- fixated instead on 404 because he mentioned sw plates.:dunce:

For the metal mud rings on plastic I'm thinking 250.4(A)(3).

 

[JFletcher]

I am student at a technical college. We were doing a project in the lab using electrical nonmetallic tubing and nonmetallic double gang boxes. The question came up as to why we could not use metal switch rings on nonmetallic boxes and I could not seem to find where specifically stated this in the 2011Nec codebook

i'd argue this exact install {ent to plastic boxes with metal mudrings) is legal if subject to chapter 8 wiring.

 

[JFletcher]

thinking about it more, why couldnt one use metal rings on plastic boxes? a switch or receptacle would have an egc and ground the ring via the screws. if it were blanked off i might see an argument but a metal coverplate could be used down the line and it woulnt be bondd or grounded

 

[user 100]

thinking about it more, why couldnt one use metal rings on plastic boxes? a switch or receptacle would have an egc and ground the ring via the screws. if it were blanked off i might see an argument but a metal coverplate could be used down the line and it woulnt be bondd or grounded

There is no prohibition or reason why you couldn't, just that you must follow the rules in 250.4 about grounding and 404 about switches -if those are followed the mudring (or metal sw plate) is bonded.

We're required anyway to tail out the egc to a switch in a nm box even if it has a plastic plate.......

 

[ActionDave]

thinking about it more, why couldnt one use metal rings on plastic boxes? a switch or receptacle would have an egc and ground the ring via the screws. if it were blanked off i might see an argument but a metal coverplate could be used down the line and it woulnt be bondd or grounded

Electrically it would work. The screws on switch are allowed to be the grounding connection to an equipment grounded metal box, but it's not code permitted to do it the other way. The metal ring would have to be equipment grounded without the switch.

 

[infinity]

The metal ring would have to be equipment grounded without the switch.

That's the way I see it.

 

[user 100]

The metal ring would have to be equipment grounded without the switch.

I forgot about that- never have thought about this before. It seems odd that they will allow a grounded switch yoke to bond a fully exposed metal face thru the screws but won't allow the same for the mudring?

Would it be in any way permissible to tail the egc to the ring itself and tie to a tapped screw? I'm fully aware of the fact that doing this would be completely ridiculous and that one could use metal boxes to start with...... just wondering

 

[ActionDave]

Would it be in any way permissible to tail the egc to the ring itself and tie to a tapped screw? I'm fully aware of the fact that doing this would be completely ridiculous and that one could use metal boxes to start with...... just wondering

A box is allowed to bond a device, a device is not allowed to bond a box. Works for me at least three hundred and sixty days out of the year.

 

[user 100]

A box is allowed to bond a device, a device is not allowed to bond a box. Works for me at least three hundred and sixty days out of the year.

I'm talking about directly tying an egc tail to a screw tapped into the metal mudring on a plastic box (op's situation), so that the ring would still be bonded sans the switch.

 

[ActionDave]

I'm talking about directly tying an egc tail to a screw tapped into the metal mudring on a plastic box (op's situation), so that the ring would still be bonded sans the switch.

Works for me.

 

[Smart $]

Since when are mud rings made to fit on plastic boxes???

 

[user 100]

Since when are mud rings made to fit on plastic boxes???

Surely some combos would interchange-(it's early, coffee's still brewing) some plastic will fit a metal box, iirc.

Besides, whats wrong with a theoretical question if it ever did come up?

 

[user 100]

Works for me.

Thanks.

 

[Smart $]

Surely some combos would interchange-(it's early, coffee's still brewing) some plastic will fit a metal box, iirc.

Besides, whats wrong with a theoretical question if it ever did come up?

Not a thing wrong with a theoretical question... just seemed the OP question and responses were more related to a matter of practicality.

 

[jumper]

I forgot about that- never have thought about this before. It seems odd that they will allow a grounded switch yoke to bond a fully exposed metal face thru the screws but won't allow the same for the mudring?

Would it be in any way permissible to tail the egc to the ring itself and tie to a tapped screw? I'm fully aware of the fact that doing this would be completely ridiculous and that one could use metal boxes to start with...... just wondering

Grounding clips would be easier. In a jam one day when the supply house did not have plastic extension rings I grabbed metal ones and grounding clips to finish, bit of a pain but passed inspection.

 

[Smart $]

Grounding clips would be easier. ...

I agree. Can't get any easier.

 

[electricman2]

Since when are mud rings made to fit on plastic boxes???

That's what I was thinking. Never seen a mud ring that would fit a plastic box