Semi-OT: again - EMT conduit

[patrick conroy]

On the advice of several - including the local inspector - I'll probably run the new circuits in my garage in EMT conduit. (And, I'll probably add a subpanel too...)

Three quick questions:

1) Do you usually just run 'romex' thru the conduit? Seems like that's the easiest thing to do. 2) Could all three (or four) circuits - two new 220, one or two new 110 runs be placed in ONE large diameter conduit, or do you have to limit it to one run per conduit? 3) How does one size conduit given the answer to #2? What diameter do I use? 4) Subpanels - *must* they be installed inbetween studs? Or can they too be mounted *on* drywall? Recall that I'm trying to not rip up the drywall in a finished garage.

Thanks!

[Swingman]

Normally, no ... although it can be done to protect the wiring in hazardous environments under many local codes, it can not generally be used as a "method of wiring".

Also be aware that you may be required to reduce the ampacity of the circuit due to heating values in some locales.

That said, I did it on many of the straight vertical runs in my shop because I had plenty of it on hand and it was passed under the "protection" provision.

You will find that separate insulated wires are the easies to handle in conduit.

Your local code will have limits as to the number of wires of a given size may be run in a conduit of a given size. There are tables for this in the NEC, and your local inspector will be able to tell you.

See above ...

There will be local requirements as to where a subpanel can be installed, required clearance, height, etc. Without question, I would anchor it to a stud.

Except for the generalizations above, and as this may change from area to area, your local inspector is really the best source for answers to your questions.

... and by all means, permit the job and get it inspected. You'll be glad you did.

[Robert Bonomi]

Romex doesn't pull easily. Particularly if you try to run more than one in the same conduit.

It's also more expensive than single-strands.

Multiple runs per conduit *are* allowed.

There are long, convoluted rules about how big the conduit must be. vs. what is run through it. basically it's a function of the 'cross-sectional area' of the conduit, and a limit on how full you can pack it. At least six strands of 10 ga. is 'legal' in 1/2" EMT. Note: I do *NOT* recommend 6 strands of #10 in a single 1/2" conduit -- it is harder-n-hell to pull past bends; direct personal experience speaking.

Two 110(120) V runs in a single 1/2" conduit is 'no problem'.

Two 220(240) V runs in a single 1/2" conduit might be a little awkward. depending on number of bends, and whether or not you pull a 'neutral' wire (*recommended* for future flexibility, although -not- needed if it is powering strictly 240V devices.)

I'd probably go with 3/4" for a dual 240 run.

Surface mount _is_ allowed. It's the 'standard' way, when installed in an _unfinished_ basement, for example.

[Jim]

All great advice. I have worked quite a bit with my local inspector though, and I have never had the impression that he would be willing to give me that much of an education in wiring. Unfortunately, the local electrical supply house won't either (they protect the electricians, and probably their own butts by not providing a lot of technical info to DIYers with a pair of brand new Kleins). Both assume you know what you are doing.

There are several good books on the subject - one of my favorites is by Rex Cauldwell and published by Taunton Press "Wiring a House". Also, the Code Check series can be helpful. The best piece of advice I can give, having pulled miles of wire, is use one size larger conduit than you think you'll ever need. It's a lot easier to get another strand or two through an "empty" conduit than it is through one that is close to capacity.

HTH,

Jim Ray, President McFeely's Square Drive Screws

[Robert Galloway]

Maybe I didn't grasp all the fine details but usually the cover of a subpanel covers the hole in the drywall. You're not going to be able to mount the panel without any marks on the drywall. If you've got to patch later anyway if you take it all out... In for an inch, in for a mile. I'd use a stud finder or whatever to find studs, cut a hole in the drywall the size of the box. YMMV.

bob g.

patrick c> On the advice of several - including the local inspector - I'll probably run

[Swingman]

During a good part of the year I deal with building inspectors almost daily, and you're right. However, you'll never know unless you ask.

I've run across some real butts, but many of them can be nice/informative if you catch them in person, and with a respectful attitude ... particularly if your local municipality is small and allows homeowners to permit their own work ... and your taxes pay their salary.

[Robert Galloway]

When fishing conduit, a two hole rubber stopper with one hole filled with a glass tube and the other connected to the blowgun on your air compressor will sometimes get to where the fish tape won't. Put a little piece of rag on a light string (kite string or fish line?), put this in the conduit, put the stopper in the end of the conduit and hit the compressed air. Has saved my butt a number of times. Folks have done this in reverse using a vacuum cleaner but I've found the compressed air more effective. FWIW.

bob g.

Jim wrote:

[dave]

[U-CDK_CHARLES\Charles]

(snippage)

When I figure conduit, I base my calculations on 25% fill--easy with a computer spreadsheet and the appropriate data.

You'll pay a bit more for the pipe, but it makes life MUCH easier.

[Bob Peterson]

[Bob Peterson]

Its not all that easy to pull romex through EMT. Get a couple spools of real wire - red, black, white, and green. Plus I don't believe their are any tables for derating Romex in conduit.

The calculations for derating the wire size are much simpler if you stick to

3 wires in a conduit.

It depends on the size of the wires you need to run inside it.

You can buy a flush mounted panel.

[patrick conroy]

Thanks Bob!

[Bob Peterson]

[William]

6 #10 in 1/2" emt is only allowed if you use very high temp wire, not common stuff. "normal" THHN is limited to 5 and THHW is only 3 in 1/2" emt

Also if you run more than 3 conductors in a conduit you have to derate the ampacity of the wire 4-6 wires it's 20% de-rate ( 80% of original ) 7-9 70% and 10-20 50% !!! Good thing is that they allreddy derate say 12 gauge THHN for "normal" use it's limited to 20 amps even though it's really rated to 30 amps and you get to use the 30 amps to caculate your derate for the above rule.

The poster should get a copy of Ugly's electrical references ( can get one at lowes, and I think maby HD too) about $9.00 and WELL worth the cost.

If your going to run EMT conduit to a box it will allmost have to surface mounted. I guess you could hack the hell out of the studs and feed it but why??