THHN and Conduit


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Old 10-12-13, 09:48 AM
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THHN and Conduit

Background: My daughter wants 50 amp 240 volt service in her shed for an electric kiln. I dug a trench and laid 1 1/2" PVC conduit from the shed to the house. At the house, I ran the conduit up the wall to the height of the basement joists and put a service entrance cap on top. I drilled through the brick and the rim joist, so I have a hole into the laundry. I am putting a disconnect box high on the laundry wall, then switching to Romex to go through the laundry and garage to the main service panel. I am using 6 gauge wire because the total run is about 150 feet (Red, Black, White, and Green for the THHN, 6-3 with ground for the Romex).

Question: Can the THHN be without protection from the service entrance cap to the disconnect box (about 3 feet), or do I need to switch to flexible conduit or try to extend the PVC into the house?

Thanks!
 
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Old 10-12-13, 10:02 AM
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Welcome to the forums.

You should be using THWN and yes..... it needs to be protected.

You can use an LB to transition from the PVC pipe into the house.

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Old 10-12-13, 10:07 AM
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Any other electricity run out there already? If so, you should look into a subpanel instead; as you can only have one feed to an outbuilding.
 
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Old 10-12-13, 10:51 AM
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My daughter wants 50 amp 240 volt service in her shed for an electric kiln.
No need for lights or other convenience receptacles?
 
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Old 10-12-13, 04:03 PM
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Your prompt replies are very much appreciated.

Yes, I have a subpanel to put in the shed; I will install receptacles.

I discussed this with an electrician before I started, and he said nothing about the THHN vs. THWN. I suppose I can sell the THHN on eBay and start over.

So rather than the service entrance, I should use a right angle and continue the conduit into the house, correct? I'd like to reduce it from 1 1/2" to be able to fit through a more reasonable-size hole. What size conduit would still be comfortable with 4 #6 wires?

Thanks!
 
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Old 10-12-13, 05:55 PM
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You could install a NEMA 3R junction box at the top of the 1 1/2" conduit and then change to 1" conduit to continue on to the panel. The least expensive way to do this is to use a 60 amp non-fusible air conditioning disconnect as the transition point between 1 1/2" and 1" conduit. You can remove and throw away the disconnect interior, you don't really need it. Through the back of the disconnect, knockout a the 1" KO and run 1" conduit directly through the rim joist and on to the panel.

I discussed this with an electrician before I started, and he said nothing about the THHN vs. THWN
Almost all THHN is dual rated as THHN/THWN, check yours to be sure since you already bought it.
 
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Old 10-12-13, 08:17 PM
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CasualJoe, I think you just saved me from a huge hassle. I'll check the wire tomorrow, but we bought it at Home Depot, and I just checked their website. The wire we bought is clearly dual rated.

I do have an AC disconnect, but I was going to use it inside the house to transition to Romex, which I think will be easier to run through the laundry and garage. Maybe I can find a 1 1/2 to 1" reducing fitting, then get a right angle for the top. The rim joist isn't an issue, I just have to deal with the brick. I should be able to drill/break a section that will accommodate the 1" conduit.

I've done quite a bit of wiring over the years, but nothing like this. I really appreciate your advice.

Ken
 
 

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