EMT code issues

9 years ago

I learned electrical wiring working for an electrician in Chicago, where all wiring must be in Electrical Metallic Conduit or BX. I like this method (even though it takes more work) and rewired my 1890s home mostly using it. I did something which, I discovered later, was in violation of the electrical code: I assumed that the conduit would serve as the ground conductor. I had to pull another wire for the ground, which was a pain. In most cases, I had to pull the other wires out, add the ground wire, then pull them back.

Another thing I did, which got by the inspector, is to a) have multiple circuits in the same conduit, and b) have a common neutral wire. I noticed that for the 240-volt wiring I was replacing for the electric dryer, a 3-wire Romex, with ground, was run to an appropriate outlet. The washer, however, was connected to the 117 volt "half" of this circuit, so I assumed that this was OK.

So, for example, if I want to run four circuits to the living room, two to be from one half of the 240 volt breaker box, and the other two from the other half. Do I have to have one, two, or four neutral wires?

A related question, what is the maximum number of independent circuits I can run through one conduit (assuming it's large enough)?

Another code violation, which I corrected, is that inside the breaker box, each circuit must have its own breaker. So, for example, I put in two lights and it's easier to run separate feeds than one, I cannot combine them on one breaker, even if each line has only a 100 watt bulb on it.

I'm building a new home and running pipe in open walls is much easier than trying to running rigid pipes up from the basement or down from the attic, which is what I did in my current home.

Sort by:Oldest

Comments (6)

randy427
9 years ago
A 240v circuit for the dryer should not be also used as a 120v circuit for the washer.
Each MWC (multi-wire circuit with two hot legs) should be powered from a two-pole breaker, to ensure the two are powered by different legs, and have one neutral from the breaker panel. So, you will need two neutrals.
There's no specified limit on the number of circuits in a properly sized conduit.
As for more than one circuit on a breaker, most breakers are designed to have only one wire connected to a terminal. You may wire nut the two together to a third wire that then goes to the breaker.
In all cases, though, your AHJ has the final word as to compliance with local interpretation of applicable regulations.
mtvhike
Original Author
9 years ago
I'm a little confused. My MWC for the dryer has two hot legs with a two-pole breaker, and one neutral (and one ground). Are you saying that the washer should have a separate 110 volt line and breaker? It's all moot now, because I replaced the dryer with a gas one.

But, if I am running two hot lines, of opposite phases, through a single conduit to separate devices, I cannot "share" the neutral, even though the current through the neutral will be less (in fact, zero of the two loads are equal). Likewise, if I were to use Romex to a junction box with two circuits, I cannot use a 3-wire Romex, but two 2-wire ones (each with a separate ground, of course). Is that correct?
Related Professionals
Alabaster General Contractors · De Pere General Contractors · Dover General Contractors · Dover General Contractors · Hagerstown General Contractors · Mililani Town General Contractors · Pine Hills General Contractors · San Elizario General Contractors · Shorewood General Contractors · Winton General Contractors · Westmont General Contractors · Mill Valley Solar Energy Systems · Verona Solar Energy Systems · Mount Lebanon Home Automation & Home Media · Pittsburgh Home Automation & Home Media
greg_2010
9 years ago
My MWC for the dryer has two hot legs with a two-pole breaker, and one neutral (and one ground).
Your dryer circuit is not a MWBC (multi-wire branch circuits). It's a single circuit that supplies 240v and 120v to your dryer. You are not allowed to split it off to power another single 120v outlet.

But, if I am running two hot lines, of opposite phases, through a single conduit to separate devices, I cannot "share" the neutral
Yes you can. That is what a MWBC is.

This post was edited by greg_2010 on Fri, Sep 12, 14 at 12:18
hexus
9 years ago
"Are you saying that the washer should have a separate 110 volt line and breaker?"

Yes
Article 210.11(C)(2) Branch Circuits Required.

(2) Laundry Branch Circuits. In addition to the number
of branch circuits required by other parts of this section, at
least one additional 20-ampere branch circuit shall be provided
to supply the laundry receptacle outlet(s) required by
210.52(F). This circuit shall have no other outlets.

"But, if I am running two hot lines, of opposite phases, through a single conduit to separate devices, I cannot "share" the neutral"

Yes you can, totally legal and commonly refereed to as an "edison circuit" (or multi wire branch circuit). I do it all the time in both conduit and with Romex. Saves time and wire. I run 12-3 romex circuits everywhere possible.

"I assumed that the conduit would serve as the ground conductor."

It can. As long as it's installed properly, you can use the conduit as a ground. Unless there's some local restriction it is not an NEC violation to do so.

"A related question, what is the maximum number of independent circuits I can run through one conduit (assuming it's large enough)?"

it depends on the wire and conduit size. You have to de-rate also depending on how many current carrying conductors there are. There's probably several conduit fill calculators on the net you can use.

" I cannot combine them on one breaker,"

If the breaker is UL listed to have two wires landed on it, yes you can. Or you could pigtail them and land it under the breaker. There is no restriction stating you can not do so.

This post was edited by hexus on Fri, Sep 12, 14 at 12:28
Ron Natalie
9 years ago
The requirement for a two pole breaker has SQUAT to do with assuring it is fed from differing legs, but to make sure that both ungrounded connectors are disconnected together.
bus_driver
9 years ago
"I did something which, I discovered later, was in violation of the electrical code: I assumed that the conduit would serve as the ground conductor. I had to pull another wire for the ground, which was a pain."
It would be good to post which/what code you are citing. Must be a state or city code and not mandatory elsewhere. NEC Article 358.2 "--for use as an equipment grounding conductor--".
It is certainly permissible, and often desirable for a number of various reasons, to add an equipment grounding "wire" in any such installation. But not ordinarily required by the NEC.