Conduit and derating

[Mike Honcho]

couldnt seem to find what i was looking for searching, so heres my question.

can i run one 1/2 emt with 2 hots, 2 neutrals, and 2 grounds 12 ga thhn, and still be good for 20 amps? or does derating come into play at that point.

and my second question is can i use the boxes for the first circuit as a pass through for the second circuit? reason being is i want to run each wall seperate, but trying to run only one conduit.

thanks.

 

[alfredeneuman]

You only need 1 grounding conductor, not 2, and if the circuits are fed from different the 2 legs (both A & B) you only need 1 neutral.

That being said, as many as (9) THHN/THWN can be run in a conduit without having to derate/upsize, so you're good to go there.

2nd question:
It's perfectly acceptable to run multiple circuits through the boxes, as long as you are mindful of the box fill limits.

 

[Mike Honcho]

You only need 1 grounding conductor, not 2, and if the circuits are fed from different the 2 legs (both A & B) you only need 1 neutral.

That being said, as many as (9) THHN/THWN can be run in a conduit without having to derate/upsize, so you're good to go there.

2nd question:
It's perfectly acceptable to run multiple circuits through the boxes, as long as you are mindful of the box fill limits.

just what i was looking for, i was aware of running, a mwbc, but having no knowledge good or bad, i was leaning away from them. i was also unaware 2 seperate circuits could share one ground.

i should be ok on box fill, i have 4 inch deep boxes with 1/2 raised covers.

thanks again!

 

[wyliesdiesels]

You only need 1 grounding conductor, not 2, and if the circuits are fed from different the 2 legs (both A & B) you only need 1 neutral.

That being said, as many as (9) THHN/THWN can be run in a conduit without having to derate/upsize, so you're good to go there.

2nd question:
It's perfectly acceptable to run multiple circuits through the boxes, as long as you are mindful of the box fill limits.

Huh? 4 or more CCCs(current carrying conductors-hots and neutrals) in the same raceway must be derated.

In the OPs case, he would be fine with 4 #12s because 90* c ampacity is 30a x 80% = 24a.

And if he went with a MWBC, then none of this applies as it would only be 3 conductors...

 

[Aceman]

I think Alfred was saying you can put 9- #12 THHN's in a pipe and still use a 20 amp breaker. After 9, derating starts cutting into the allowable ampacity pretty hard.

 

[alfredeneuman]

I think Alfred was saying you can put 9- #12 THHN's in a pipe and still use a 20 amp breaker. After 9, derating starts cutting into the allowable ampacity pretty hard.

This is EXACTLY what I meant!

 

[zmaxmotorsports]

What are you running off these circuits,how far and how many bends between boxes?
Personally Id rather run 3/4" pipe than fight pulling 9 #12s through a piece of 1/2",you can always drop it down to 1/2" as you drop circuits off along the way.
And remember if you run a ground wire through the pipe it should be bonded in each box.

 

[Mike Honcho]

i am also staying away from mwbc because i have enough single pole breakers.

so if am understanding alfred right, i can run 2 hots, 2 neutrals, and only one ground? so 5 wires in total?

 

[zmaxmotorsports]

Yes

 

[Mike Honcho]

Yes

Perfect! Off to work

 

[Mike Honcho]

Something just dawned on me, would the fact that each circuit will start with a gfci outlet change the fact that they can share a ground?

 

[sberry]

No, the ground doesn't have anything to do with the operating part of the gfci. Its simply a bond or low impedance pathway back to the service neutral.

 

[2Big2Ride]

Personally Id rather run 3/4" pipe than fight pulling 9 #12s through a piece of 1/2",you can always drop it down to 1/2" as you drop circuits off along the way.

Did this same thing using 3/4" EMT and nine 12g solid THHN wires and about 250 degrees of bends to the first box, would not have wanted to try it with 1/2" EMT .