#8 AWG THWN and PVC conduit


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Old 11-17-15, 12:40 PM
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#8 AWG THWN and PVC conduit

I am running a 240 40 AMP line to a GFCI cut off for a hot tub. I am running THWN and want to know if I can run the 4 wires in 3/4 PVC conduit or will I have problems fitting and snaking all 4 wires in 3/4? Based on the size / thickness of the #8 there is enough room. I am also wondering if having 2 hot wires and neutral in the 3/4" results in a drop of power issue? I have read you can loose 20% in amperage with too many current carrying wires. Thanks
 
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Old 11-17-15, 12:45 PM
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Yes four #8 THWN will fit legally in a 3/4 PVC conduit as long as you follow standard rules for conduit routing and bending. All circuit conductors (H-H-N-G) must travel in the same conduit. The potential for overheating occurs when you have multiple circuits in the same conduit, not multiple wires of the same circuit.
 
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Old 11-17-15, 12:51 PM
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ibpooks thank you. I thought that was the case, but I was not sure if 3/4 would be too tight and cause a problem and I should go to 1". Fortunately most of the run is in a crawl space, and being an 1840 farm house I have easy access from crawl space outside. Starting at the bend under the house to outside, all will be in conduit. Fortunately it is then a short run up to the box, and then down and under ground to the hot tub so the PVC will not be long pulls with snake. I assume the crawl space run does not need to be in PVC but secured to joist.
 
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Old 11-17-15, 01:00 PM
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The conduit MUST be continuous between the supply and point of use. You cannot have individual wires outside of conduit. Further, you cannot have more than the equivalent of four 90[SUP]o[/SUP] bends between access points for pulling the conductors.

Also, you do not need to use #8 for the equipment grounding (green) conductor. With #8 power conductors a #10 equipment grounding conductor is fine.
 
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Old 11-17-15, 01:24 PM
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Furd if the wires are indoors still conduit? If so, thank you. I was not aware having never used THWN before. Good to know. And I only will have 4 90's including the two to make a 180 out of the house
 
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Old 11-17-15, 01:27 PM
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Type THHN/THWN conductors must ALWAYS be used in conduit, no exceptions.
 
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Old 11-17-15, 01:33 PM
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Furd, thank you for helping me avoid a major mistake.
 

Last edited by Ted Axelrod; 11-17-15 at 01:35 PM. Reason: Wrong name
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Old 11-17-15, 06:04 PM
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Instead of 90 you may want to look at LBS or pull ells.
 
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Old 11-23-15, 12:49 PM
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Thank you

Thank you everyone for your help.

The project went without a hitch and the Hot Tub is now converted to 240 and it has never run so hot. Bring on winter.
 
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Old 11-23-15, 01:59 PM
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Good news. Just don't stay in till you prune up.
 
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Old 11-23-15, 03:38 PM
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You probably know this, but don't set the temperature higher than 104F.
 
 

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