PVC conduit and pvc junction boxes - good idea or bad?

[mooltan]

Hey all,

I'm putting some 1 ph 220 and (via a converter box) some 3 ph in a garage shop.  I'm
planning on mounting PVC conduit up high exposed at the top of the walls and
across the ceiling.  There are outlets lower on the walls and on the ceiling over
machines that will need it.

My question is whether PVC is a sane way to do this.  Specifically:

1.  PVC seems a bit easier to work than emt, and it'll cost less.  Any opinion on it good or bad
     (assuming it meets local code)?

2.  What do you use for junction boxes?  I've found these CANTEX "conduit bodies and Junction Boxes" things
     that might work, but is that what people do?  I'm more familiar with the metal square (ish) boxes and
     knock outs and such used as a junction box (as well as for mounting other stuff). 

3.  If you have to come down a wall and across the ceiling at the same point, do you run a T for the down
     and a sweep ( elbow) to get out across the ceiling? 

4.  Anything wrong with using a regular old metal box for outlets and such (or even junctions I guess)
    as long as you ground them?  I can get pvc adaptors that go plastic to threaded for the nipple.
    I can't seem to find any "normal" looking boxes for surface mounting on a wall for outlets and
    switches.  Maybe I'm not looking hard enough.

5. If you have to switch 220 is there a two pole switch that's big but "conventional" looking?  I have
    one on the front of my welder for example, but I can't find any switches to switch 30 or 50 amps
    that aren't either disconnects or big expensive throw boxes - not that a throw box is bad.  I'm just
    looking for an on/off in front of the phase converter box - not a disconnect for the entire thing. 
    I'm happy with a 2 pole disconnect for the entire shop.

6. What's the standard for a three phase plug?  I was going to use a 4 wire rotating locker but is
    there any other convention that keeps people from hooking a 1 phase piece of gear to a
    3 phase line?


Anyway that's it (that's enough...) This site is a great resource.  If anyone has any hints or
opinions on this stuff I'd be glad to hear it. 

Regards,
mt

[JP]

1)   I see no reason you cannot use PVC if it meets local code, It will be fine.

2)   They do make PVC junction boxes, you can find them with hubs but some you will need to drill and use male adaptors.

3)   They make many pre-fab fittings for PVC or you can use a heat blanket to bend it.

4)   You can use metal boxes for the devices or PVC ones.

5)   The best you will probably do for a switch is a disconnect, you can get the ones that look like a switch.

6)   A twist lock cord cap is the way to go, each one is designed for volts, amps and phase, they will not plug in to the other if it is wrong.

Hope it helps!
   

[mooltan]

Hey, thanks for the info -

Another thing - an ex electrician laughed at my idea of putting
8 or so  8 ga THHNs down a 1 inch conduit run. 

What would real people use for that many 8's?

Thanks again.

mt

[JP]

According to Annex C, table C.9 of the 2008 National Electrical Code,  Seven #8 conductors are allowed when using THHN in 1” PVC Conduit Schedule 80. Having said that it varies with different types of wire and conduit.