Getting ready to wire my workshop which should be completed next week. Is there a chart for how many 20 amp circuits I can run in each size of metal conduit? I want to run two for the lights, with one pipe coming off of the panel- is there room for a couple plug circuits as well if I step up to 3/4? Also, I need to make a shopping list so I will need to know the different sizes I need at each point. Also, do I need to run multiple ground wires, or can all circuits in the line tie into 1 ground?
Conduit Size Chart
- Thread starter Bearkat
- Start date
PelicanPines
ALLIANCE MEMBER
Also interested to know this. I'm added a few outlets and plan on running conduit.
Beemer533
Well-known member
Here is a pdf with the fill allowances..
Here is a calculator.
I think these are a couple years old, but I don't think fill maximums have changed..
I think you can share an egc as long as it is sized correctly, but I'm sure someone will chime in that knows what code actually says.
Here is a calculator.
I think these are a couple years old, but I don't think fill maximums have changed..
I think you can share an egc as long as it is sized correctly, but I'm sure someone will chime in that knows what code actually says.
JohnX14
Well-known member
If you mean EMT (Electrical Metallic Tubing) and are using #12 THHN you can fit the following number of condutors in each size:
1/2" - 9
3/4" - 16
1" - 26
1 1/4" - 45
1 1/2" - 61
Obviously you need 2 condutors for a 120 or 240 volt circuit and 3 conductors for a 120/240 V circuit.
But you also have to derate the ampacity of #12 based on the number of circuits using table 310.15(B)(3)(a) for more than 3 current carrying conductors in a raceway. (Though you begin your derating based on #12 having an ampacity of 30A)
There are other factors that may require additional derating.
There is not a one stop chart to explain what you are trying to accomplish. But what I listed above are the 2 most common considerations. If you give me more specifics of what you want to install I can answer better.
1/2" - 9
3/4" - 16
1" - 26
1 1/4" - 45
1 1/2" - 61
Obviously you need 2 condutors for a 120 or 240 volt circuit and 3 conductors for a 120/240 V circuit.
But you also have to derate the ampacity of #12 based on the number of circuits using table 310.15(B)(3)(a) for more than 3 current carrying conductors in a raceway. (Though you begin your derating based on #12 having an ampacity of 30A)
There are other factors that may require additional derating.
There is not a one stop chart to explain what you are trying to accomplish. But what I listed above are the 2 most common considerations. If you give me more specifics of what you want to install I can answer better.
JohnX14
Well-known member
Yes they can share a grounding conductor. They can even use the raceway as the ground, but I would not advise it. (Perfectly legal, but problem if even one screw is not properly torqued)
Thanks for the iput. My goal is to only have a few runs of Conduit coming off of my panel and splitting them down the line. I plan to run all 20 amp circuits for plugs and lights. As an example, I would like one run with both light circuits as well as a plug circuit. I could have junction boxes along the wall to drop plugs and run to lights. same thing on the other side with 3 different plug circuits.
JohnX14
Well-known member
Sounds like you can run 3/4" in each direction. You can either stay 3/4" for everything or drop down to 1/2" if you want. The price difference is so little I'd stay 3/4 as it looks a little better. For this few circuits even with derating, you can stick with #12.
Charles (in GA)
Well-known member
You are better off with more pipe runs, and fewer circuits in the pipe. One reason is that it is extremely difficult to pull additional wires in a pipe after the originals have already been pulled, You either have to plan well ahead and pull all of them at once (how many spools of wire do you have 
)
One limiting factor is that more than 9 current carrying wires in a conduit triggers derating for all of the wires in the conduit.
I ran lots of ½ EMT and generally did not pull over four current carrying wires plus grounds, in the conduit. Typically I have three receptacles on a circuit.
Charles
Just a little bit of my "mess 'O pipes".................... and its been added to since this pic was made...............
)One limiting factor is that more than 9 current carrying wires in a conduit triggers derating for all of the wires in the conduit.
I ran lots of ½ EMT and generally did not pull over four current carrying wires plus grounds, in the conduit. Typically I have three receptacles on a circuit.
Charles
Just a little bit of my "mess 'O pipes".................... and its been added to since this pic was made...............
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wyliesdiesels
Well-known member
Yes an EGC can be shared. It must be the same gauge as the largest ungrounded conductor!!
Charles (in GA)
Well-known member
Yes, we've had that argument before. I agree with you, run grounds, then if the conduit becomes separated for whatever reason, or doesn't make good contact at the panel, you still have a ground. Others go "you are wasting wire, you don't need it, it won't do any good, blah.... blah....." I'm in the run the ground and never worry camp.
Charles
alfredeneuman
Well-known member
It can be shared but it needs to be sized to the proper ground wire for the biggest circuit in the conduit, not the biggest ungrounded conductor.
#14 for 15 amp circuits
#12 for 20 amp circuits
#10 for 30 - 60 amp circuits
#8 for over 60 - 100 amp circuits
#6 for over 100-200 amp circuits
teamextreme
Well-known member
ummm, that's exactly what he said. You just re-worded it using laymen's terms.
TheEquineFencer
Well-known member
Personally, if possible, I'd do my runs in 3/4 and stay away from 1/2 EMT, 3/4 is easier to pull wire through even after you have other circuits pulled with a good fish tape. I just added a 140 foot circuit of wire through a 3/4 conduit that I already had two other circuits pulled through, it was easy. I do most of my offsets on 30* when possible. Speaking of fish tapes, I'm not sure if all tapes are the same, but the Klein I have has the feet marked on the tape, it makes figuring wire lengths easy.
alfredeneuman
Well-known member
ummm, that's not exactly what he said.
"It must be the same gauge as the largest ungrounded conductor!!"
If you put a #6 in conduit, you're not required to run a #6 ground, but a #10.
wyliesdiesels
Well-known member
Youre right. Im not sure where i came up with that.
teamextreme
Well-known member
Oops, my bad too. I didn't catch exactly what you said. You're correct.