Conduit Fill

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John Valdes

John Valdes

Senior Member
Location
SC.
Occupation
Retired Electrician
Hello everyone,
I have been out of the trade for a while now. My most current code book is 1996.
Question: I want to run a 100 amp feeder/service to a small cabanna (sub Panel). The conduit is 1 inch PVC. The conduit is already in the ground. According to my code book, I need # 3 THHN for the sub panel feeder conductors. And the max conduit fill is (3) number 3 wires for this. I need to get a # 8 in this conduit for the ground wire. The ampacity table is 95 amps for #4 THHN. Should I pull # 4 instead, use a 60 amp breaker, then when I pass the inspection change the 60 amp breaker to a 100 amp breaker? Whats five amps?
Thanks.....John
 
Get a new code book. Art. 250.32 will allow you to re-establish a neutral ground bond at the out building. So you won't have to pull an equipment grounding conductor. Or install a 90 amp breaker. No one here would ever suggest you install a non compliant job before or after your inspection. Good luck.
 
John Valdes said:
.... then when I pass the inspection change the 60 amp breaker to a 100 amp breaker?
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yea...that's what you should do.

Get serious...do it right or hire some one who can do it right.
 
As far as conduit fill goes , 3 number 3AWGs and a number 8AWG amount to only a 34% +/- fill.
40% is the max.

ibew441dc
 
It is understandable to be rusty on code requirements,

BUT UNACCEPTABLE TO INSTALL CODE VIOLATION'S

ibew441dc
 
Cody K said:
thhn is oil and gas resistant. underground residential installation will not be a problem
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Cody welcome to the forum.:smile:

Any time you install conductors under ground they must have a "W" in the description. THWN, RHW THW etc.

If the wire is only marked THHN it can not be installed in a wet location. Any underground location is considered wet.

Check 300.5(D)(5)
 
celtic said:
yea...that's what you should do.

Get serious...do it right or hire some one who can do it right.
Click to expand...

I should have never mentioned changing breakers. I would never give that advise to anyone either. ps....Why should I hire someone when number one I am a master electrician and number two I have found you guys.....Thanks
 
ibew441dc said:
As far as conduit fill goes , 3 number 3AWGs and a number 8AWG amount to only a 34% +/- fill.
40% is the max.

ibew441dc
Click to expand...

ibew441dc,
I worked out of local 349 Miami Fl. in the early 80's. Nice to meet you. Are you sure about your statement. I have only a 1" PVC conduit.
 
rcarroll said:
Get a new code book. Art. 250.32 will allow you to re-establish a neutral ground bond at the out building. So you won't have to pull an equipment grounding conductor. Or install a 90 amp breaker. No one here would ever suggest you install a non compliant job before or after your inspection. Good luck.
Click to expand...

rcarroll,
Thats what I thought. The inspector has already told me that he wants to see a four wire feeder. His point was that if I used a three wire feeder then I would be required to drive a ground rod. Since the out building is close to the lake his concern is that the resistance to ground would be less than the resistance at the main panel.......Thanks John
ps....the 90 amp breaker is a very good suggestion.
 
benaround said:
THHN ??? for underground
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Benaround,
Thanks for that advise. I spent so much time in the industrial field it just seemed natural. Is the THWN the choice for this job. PVC conduit.....Thanks
 
iwire said:
Cody welcome to the forum.:smile:

Any time you install conductors under ground they must have a "W" in the description. THWN, RHW THW etc.

If the wire is only marked THHN it can not be installed in a wet location. Any underground location is considered wet.

Check 300.5(D)(5)
Click to expand...


I don't doubt you but 300.5(D)(5) does not exist anymore.

Tom
 
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