Can I use metallic junction boxes w/PVC conduit?


Old 08-11-03, 08:40 PM
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Question Can I use metallic junction boxes w/PVC conduit?

Subject says it all...but here's more info...I'm installing a new fan in my frontroom where none existed before (there's nothing there, no power, no box, nothing). I had previously installed motion sensor lights outside. Since I ran a new 20A circuit for this I decided to tap into it for power to the new order to make my life a little easier in the future I wanted to run a few wires for "future" circuits and just leave them capped off in a box. To make it easy to pull the cable and to add even more if I decide to later I started using 1" PVC conduit (this is all inside). Problem is that Home Depot doesn't sell the connectors or boxes for 1" PVC conduit. Can I use metal boxes w/the PVC conduit?

I suppose I have one other question...can I use liquid tight flexible PVC conduit in the attic connected to the rigid PVC and to a metal box (too hard to run rigid conduit in my attic)?

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Old 08-11-03, 08:55 PM
P Michael
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Yes, you can. One way to do this is to cement a slip/male thread connector onto the end of the PVC conduit. Insert this into your box and fasten with a 1" lock nut.
But wait, there is a catch. You are using 1" PVC conduit. Now you need holes suitable for 1". You may have to get large metal boxes [4 11/16"] which have punch-outs for 1". Or you can use normal metal boxes but will have to enlarge the 3/4" hole for the 1" fitting. This is an excuse to buy a tool. I would use my Greenlee 1" hole punch [~$60] or my large [1 3/8"] UniBit [~$50] or, last choice, a 1 3/8" hole saw. In your case, the hole saw option would be cheapest [<~20?] but tedious. Actually then, just get a box with 1" knock-outs. Next time use 3/4" conduit.
Also, PVC is not conductive so it needs a green ground wire.
Old 08-12-03, 08:06 AM
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Thanks for the info. Would using metal boxes w/PVC be acceptable to an inspector?
Old 08-12-03, 07:15 PM
P Michael
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Both PVC and EMT are recognized raceways. Typically, PVC is used for underground work and the metal raceways used for interior work. There is sometimes a concern about PVC used in interiors since, during a fire, it releases poisonous fumes. But this may be a concern more with schools and such but it may be in a local code or in spec. sheets. In that case, the usual practice is to transitition from PVC to EMT as soon as possible. That is, cut off the PVC about 2" above the concreate, add a slip/female threaded coupling and then screw in an EMT connector without the locknut. You get a free locknut this way. But I wouldn't worry about it. Using conduit and boxes will probably impress your inspector.
Don't know about liquidtight flexible PVC conduit. Usually you can use rigid if you bend it. It will soften in boiling water or the equivalent heat.
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