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-   -   Replacing Metal timer box with Plastic - Metal conduit question? (http://www.diychatroom.com/f18/replacing-metal-timer-box-plastic-metal-conduit-question-89822/)

TFastle 12-17-2010 10:49 AM

Replacing Metal timer box with Plastic - Metal conduit question?
 
I am replacing a mechanical 120v (Landscape light) timer in a metal box with a "GE Digital Time Switch" in a plastic box. I gather from the instructions if I have metal conduit coming into the box I need to use a jump wire to tie the metal conduit together (I have two metal conduit and one pvc). Does this mean basically only using a jump wire from one of the metal conduits to the other? Do I need to tie that jump wire into the "bundle" of grounds I will be wire nutting together in the plastic box as well? I am guessing not but want to make sure. Also, is there a real risk if I don't "jump wire" them across the plastic box? I am going too but was curious how necessary it is. Also, is there a good way short of going and buying grounding bushings to connect my jump wire to the metal conduit? Thanks very much for your help!!

J. V. 12-17-2010 03:08 PM

Yes, it is a risk to ignore the ground wires. The ground wire from the panel will connect to all the grounds in the box. All grounds get connected to each other. If the plastic switch has a ground terminal, use it too!

Saturday Cowboy 12-17-2010 09:41 PM

Quote:

Originally Posted by TFastle (Post 552663)
Also, is there a good way short of going and buying grounding bushings to connect my jump wire to the metal conduit?

nope those are required. all grounds, conduit, switch, etc need connected

TFastle 12-18-2010 09:17 AM

Bonding the metal conduit?
 
In my reading on the subject I gather what I need to do with regard to the two metal conduits coming into the box is "bond" them. Run a ground wire from one to the other but that wire does not need to be tied into the bundle of ground inside the box. Is this correct in your opinion? I could not locate any 3/4 conduit nuts with clamps to run the wire inside the box so am going to use clamps on the outside of the metal conduit and run the ground wire (bonding wire) on the outside of the box. Any problem with that? There is no ground wire inside the plastic box and I did tie all other ground wire together. Thanks very much for your help!

J. V. 12-19-2010 11:23 AM

You don't need bonding bushings, you need all the ground WIRES connected to each other. You are making this way to complicated. If its a ground wire it gets connected to the other ground wires. You are under some impression the conduit needs bonding, it doesn't. Just connect all the grounds together and anywhere there is a ground lug connect to that too.

Bonding and grounding are not the same.

TFastle 12-19-2010 11:34 AM

Bonding vs Grounding vs Code?
 
Thanks JV and I would tend to agree ... probably more complicated than needed. What you described is exactly how in installed it. In the instructions it also said that since the box was plastic there was no ground connector, to connect all ground wires together and, that if there was metal conduit coming into and out of the the box to "bond" them. In reading on "bonding" I gather it means to keep continuity of the metal conduit from it's origination to it's end point and in this case it would mean a jump wire across (or around) the box. Not being an expert I am not sure why you need this but my guess is that it acts as a back up to the ground wire or insures the ground wire is indeed grounded. If it has any value or I should do it to maintain code I want to. Thanks for any additional input.

Saturday Cowboy 12-20-2010 05:54 AM

Quote:

Originally Posted by J. V. (Post 553649)
You don't need bonding bushings, you need all the ground WIRES connected to each other. You are making this way to complicated. If its a ground wire it gets connected to the other ground wires. You are under some impression the conduit needs bonding, it doesn't. Just connect all the grounds together and anywhere there is a ground lug connect to that too.

Bonding and grounding are not the same.

Please explain why when interrupting a metal conduit run with the replacement of a metal box with a plastic box, that he does not need to in some way repair the bonding path of the metal box. In my understanding, now that there is a plastic insulator in the middle of a metal raceway, don't we have to fix this?

OP "bonding" is what most branch circuit ground wires are doing, making sure all metal parts are at the same potential.


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