Wire / Circuit limit in EMT 1/2"

[icnsltmfg]

Wire / Circuit limit in EMT 1/2" or 3/4"

I am trying to plan out the conduit for the garage, and it looks like I will have one of the EMT runs with the following....
1 20amp lighting on a 3 way (3 wires) #12 THHN
1 20amp outlet (2 wires) #12 THHN
1 30amp 220v (3 wires) #10 THHN
and possibly 1 15amp lighting (2 wires) #14 THHN

Is that too many wires in 1/2 or 3/4 EMT and are my sizes / gauge correct?

 

[Stuart in MN]

The short answer is yes, that's too many wires. Also, you can have only so many hot wires in the same conduit before you have to start derating the wire's current carrying capacity - 1 to 3 hots there's no derating, 4 to 6 derate 80%, 7 to 9 wires 70% and so on.

Do some google searches on 'conduit fill' and you'll find some online calculators that will help you figure out how many conduits will be needed and how big they need to be.

Also, is this conduit going to be underground? If so, EMT isn't the right choice - go with PVC.

Edited to add: take a look at this page, it describes the process electricians and engineers have to go through to size conduit. You can see it's not a simple process. http://www.selfhelpandmore.com/homewiringusa/2002/definitions/calconduitfill/index.htm

 

[icnsltmfg]

It is all going to be surface mounted inside the garage....
what would you recommend? Running two pipes next to each other?

 

[markb1]

My calculations say 3/4" EMT

Area of #12 thhn copper.0133 sq. in. X 5= .066
" #10 .0211 X3= .063
" #14 .0097 X2= .019
Total .148

max fill for 1/2" emt .122
Max fill for 3/4" emt .213

Use 3/4" EMT
Breaker size is correct.

 

[Aceman]

If your 30amp recep is fairly close, say within 20-30 feet, I'd definitely consider running a 1/2" emt for just this. Then put everything else in the other 1/2" emt. This way you won't have one pipe with a dozen J-boxes splitting off everywhere and this will leave you with some extra room for possible future circuits.

 

[rockwithjason]

My calculations say 3/4" EMT

Area of #12 thhn copper.0133 sq. in. X 5= .066
" #10 .0211 X3= .063
" #14 .0097 X2= .019
Total .148

max fill for 1/2" emt .122
Max fill for 3/4" emt .213

Use 3/4" EMT
Breaker size is correct.

Mark hit this one on the head. Derating is not a factor here if you use 90 deg rated wire such as thhn.

 

[markb1]

Thanks for the support Jason.

Mark
IBEW LU #595

 

[kbs2244]

Amen to Jason and Mark.
That not only makes it legal and safe, but it is a WHOLE LOT easier to pull the wire.

 

[icnsltmfg]

Sounds good to me.....you guys are great.