2 circuits in the same conduit OK?

[gearheads78]

I am getting ready to wire my new shop and I want every other plug down the walls to be on separate breakers. Can I use a single conduit down the wall with wires inside form 2 separate breakers?

 

[tfi racing]

Not sure about the NEC,but the CEC does have a limit on the number of circuits in a conduit.Can't remember the exact number or rule,but it is around no more than 200.You should be OK.

 

[kbs2244]

Go for it.
I even put two duplex outlets in one 4x4 box.
Each on a seprate breaker.
Two circuits, one box.

 

[mrb]

after you have 9 current carrying conductors in one conduit derating progresses to the point where you have to increase wire size. 2 circuits, youre fine.

watch out for those suggesting a MWBC or 2 hots and one neutral if you need GFCI protection. the neutral cannot be shared downstream from a gfci.

 

[Berserker]

So these big conduits, they are full of different circuits. There is an area in the code for fill, and derating. Don't jam it full, and you will be ok. Not to mention its esier to pull wires in a cable that is not full.

The one thing I would pay attention to, is not putting different voltages in the same conduit. 120 and 240 is ok. But don't run phone and such. They do make 600v insulation for communications wire. If you did that, then ok.

 

[gearheads78]

Thanks for the input. It will only be a couple of circuits

 

[mrb]

They do make 600v insulation for communications wire. If you did that, then ok.

nope. even with 600v insulation you cant put a class 2 circuit in a conduit with power.

 

[Berserker]

We do it in cable tray all the time. Either put a divider between them or insulation rated for 600 volts.

 

[annoyingrob]

Go for it.
I even put two duplex outlets in one 4x4 box.
Each on a seprate breaker.
Two circuits, one box.

Just a quick question on this. If you put two separate circuits into the same box, do you need to label the box inside somewhere indicating as much? I would hate to have someone open up the box, assuming they've turned off the power, only to realize that there's a 2nd circuit in there.

 

[mrb]

We do it in cable tray all the time. Either put a divider between them or insulation rated for 600 volts.

we're not talking about cable tray here, and you cannot run class 2 circuits in the same conduit as power. i dont remember the code section off hand -it might be 725.

 

[bochnak]

Conduit fill chart:

http://www.westernextralite.com/resources.asp?key=47

Other info on right of page under "Electrical Tables".

 

[Mickey O]

You'd probably be best running a MWBC (multi-wire branch circuit) provided your house has 240V and you have space for a double breaker (you can move breakers around to make space). Use a double circuit breaker that is tied together and run one black and one red (or other hot colors) wire and one neutral, be sure to pigtail off the neutrals (not use receptacles). You might even install 1900 boxes (4 x 4's) for each place you want a receptacle and put two (be sure to keep the same circuit on the same receptacle, say all of the reds on the right for example so you'll know), one from each circuit (cost wouldn't be much more than a dollar a box). With the MWBC you can even install a few 240 receptacles along the way.

 

[ddawg16]

after you have 9 current carrying conductors in one conduit derating progresses to the point where you have to increase wire size. 2 circuits, youre fine.

watch out for those suggesting a MWBC or 2 hots and one neutral if you need GFCI protection. the neutral cannot be shared downstream from a gfci.

Most accurate answer....

The reason for not using MWBC with a common common is because a GFI works off the concept that any current going out the hot has to equal the current coming back on the neutral. Since all outlets in a garage have to be on a GFIC, if you use a common neutral, then then neutral is going to have the current of both hots on it...causing false trips.....