Outdoor and Underground Conduit

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rchesterton
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Outdoor and Underground Conduit

Post by rchesterton » Tue Oct 08, 2019 8:21 am

What is the best conduit to use to bury a line that will eventually be used for a lamp post? I have a patio going in today and I need to get conduit for the installers to be able to lay that down before they do the rest.

I could use rigid PVC type because it is a straight run - no real turns but it will go downhill after about the first 10 feet. Should I just get some flexible non-metallic conduit to go under the pavers?

Also, does it need to go under the crusher run or can it be buried in the crusher run?
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Aaron
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Re: Outdoor and Underground Conduit

Post by Aaron » Tue Oct 08, 2019 9:29 pm

No you definitely need to use straight 10-foot sections of PVC tubing for burial. It has some bend to it so it should conform to the profile of the land.

You can use those turn fittings as needed. But that flex stuff you posted above is not suited for burial.

But to power a lampost? You can bury 14/2 Type UF-B cable (USA) or Type NMWU (Canada) without any conduit at all! That's the way to go.

You just need a conduit riser where it comes out of the ground into the building.

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Aaron
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Re: Outdoor and Underground Conduit

Post by Aaron » Wed Oct 09, 2019 12:42 am

Reading the pic you posted above, I guess it is suited for burial. But I wouldn't use it because it's unnecessarily expensive when you can just direct-bury 14/2 (Type UF-B or NMWU).

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emtnut
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Re: Outdoor and Underground Conduit

Post by emtnut » Thu Oct 10, 2019 8:23 am

rchesterton wrote:
Tue Oct 08, 2019 8:21 am
Also, does it need to go under the crusher run or can it be buried in the crusher run?
It needs to be 18" underground ! How much crushed stone you putting down ??
(12" if your under NEC, and it's GFCI protected)

Also, agree with Aaron. PVC will bend (or you can heat it with a heat gun). But I'd go with just the U/G cable, especially just for a lamp post.
~~ Ford Ford Ford Ford Ford Ford :mrgreen: ~~

rchesterton
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Re: Outdoor and Underground Conduit

Post by rchesterton » Thu Oct 17, 2019 8:49 am

Thanks for the input - I went with PCV conduit and it went perfectly. I didn't realize that there was cable that was designed to be directly buried without conduit. Good to know.

When I run a line from my exiting box through my basement to the external wall (it'll just be a dedicated, 15 amp circuit, with a single switch for the lamp post) will I have to transition to THHN once outside and going through conduit? Or, can I simply strip the insulation off of the rest of my line and continue without any break or junction going from inside to outside? It seems like the best thing to do is keep it as continuous as possible (less points for possible failures).

I suppose I should also ask...since it is an outdoor application, would I need to get a GFCI type breaker?

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Aaron
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Re: Outdoor and Underground Conduit

Post by Aaron » Thu Oct 17, 2019 1:25 pm

Yeah you need THHN through conduit. White, black, and green. It's ideal to run the conduit between panels but that can be tricky, so you'd need a junction box to transition from NM to THHN conductors.

rchesterton
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Re: Outdoor and Underground Conduit

Post by rchesterton » Thu Oct 17, 2019 5:48 pm

Is it ok to get stranded or does it need to be solid THHN?

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emtnut
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Re: Outdoor and Underground Conduit

Post by emtnut » Fri Oct 18, 2019 5:07 am

rchesterton wrote:
Thu Oct 17, 2019 5:48 pm
Is it ok to get stranded or does it need to be solid THHN?
Solid is MUCH easier to wire nut !!!
If you get stranded, I'd suggest using Wago lever nuts instead of wirenuts.

As for the wire itself, makes no difference.

As for GFCI, it is only required on receptacles. Having said that, if this light is on a metal pole, personally I would add the GFCI protection.
Depending on your panel, some of those breakers can be pretty pricey, so you could go with a GFCI receptacle and feed the light from the load side of it.
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