# Working with PVC Conduit



## McSteve (Dec 8, 2009)

#1: If you do run cable in the conduit, it has to be UF. Underground conduit is considered a wet location. You should really consider running individual THWN wires instead.

If you are just going to run one circuit or a MWBC for now, here's how I dealt with PVC in that situation:

Get a 6" PVC junction box. It should come with no holes or knockouts in it. You can then drill your own holes, one for the PVC conduit to enter, with an appropriate adapter, and one or two for Romex clamps. You can then bring your Romex to the PVC junction box, and splice to the incoming wires from the conduit inside it.


#2: See the second sentence of #1, above. As long as you're using UF cable, it's perfectly acceptable, and indeed required, to use conduit to protect the cable wherever it is not at burial depth. The conduit may get water in it, there's not much you can do to prevent that. Even a totally sealed conduit underground will get water in it.


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## jasonnewyork (Sep 9, 2009)

Thanks McSteve.

#1 - I downloaded the Carlon catalog and see they offer single and double gang gray boxes w/o any holes. I also saw the 6" j-boxes too. I like that idea - makes sense. I have to goto HD tonite and see if they sell those items. 

As for wires, I forgot to ask that question too. I'm not allowed to run regular 12-3 inside the 1" conduit to the garage since it's not "wet" rated? I guess I could could buy THWN 12ga wire in red, black, and white to achieve same goal and be code compliant. 

#2 - My plan is run 14-2 UF from the light switch in house all way to the light pole outside. So what you are saying, it's alright to NOT use bushings since the conduit is being used to protect the wire till it reaches the correct burial depth? It's my understanding that min depth is 18", is that correct?


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## secutanudu (Mar 15, 2009)

Do yourself a favor and oversize your conduit for your lamppost to a bit, maybe 3/4". Easier to pull the wires.


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## McSteve (Dec 8, 2009)

jasonnewyork said:


> Thanks McSteve.
> 
> #1 - I downloaded the Carlon catalog and see they offer single and double gang gray boxes w/o any holes. I like that idea - makes sense. I have to goto HD tonite and see if they sell those items.
> 
> ...


If I understand right, you'll have conduit coming out of the house, turning down into the ground to UF burial depth, and ending. If so, then yeah, you don't have to do anything special to the end of the conduit. As far as burial depth goes, I think the NEC says 24" for UF, unless it's on a GFCI. I'm not sure, but it sounds right, because it's 18" for PVC conduit. Someone else can chime in and confirm those depths.


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## jasonnewyork (Sep 9, 2009)

secutanudu - not a bad idea to oversize. I plan to run 14-2 UF thru the 1/2" conduit. It's only gonna be 3ft at the most, just to protect the wire as it pops out side of my house and into the ground. Still think I need 3/4"? I guess it's really not a big deal?


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## jasonnewyork (Sep 9, 2009)

I have the book "Wiring Simplified" and have to read again. I was confused about the burial depths for UF, conduit, etc. I live in Nassau County, NY and believe we are on NEC 2002 - someone correct me if wrong.


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## VRP (Jul 22, 2010)

I've never known an electrical inspector to approve/pass a cable in a conduit under any NEC or CEC edition, unless it's a short vertical piece not exceeding 3 or 4' total, to protect the cable against mechanical damage above the ground or floor. Normally it's cable or conduit but not both.

Secondly, a detached garage may be fed for one 120V 15A circuit as a branch circuit w/o more. That means only 3 wires:
1 hot
1 neutral; and
1 ground
If fed by 3-wire cable (2 hots) it cannot pass inspection because the possibility is HIGH for a 2d circuit to be similarly connected.

For two or more circuits in the garage, IIRC the structure MUST be supplied by an [ungrounded] and properly sized Feeder, to a panelboard, and there be grounded in an acceptable (code compliant) manner as any other structure, like a house. 2008 and prior NEC. I'm not sure if this requirement goes back to the 2002 edition or not, but IMO it would be wise to do it this way in either event.

Vic
Industrial &
Commercial Electrician


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## rjniles (Feb 5, 2007)

VRP said:


> I've never known an electrical inspector to approve/pass a cable in a conduit under any NEC or CEC edition, unless it's a short vertical piece not exceeding 3 or 4' total, to protect the cable against mechanical damage above the ground or floor. Normally it's cable or conduit but not both.
> 
> Secondly, a detached garage may be fed for one 120V 15A circuit as a branch circuit w/o more. That means only 3 wires:
> 1 hot
> ...


A detached garage may be fed by a MWBC (multi-wire branch circuit) using 2 hots, 1 neutral and a ground. They may be 20 amps. The circuit breaker must be a 2 pole, common trip breaker. This is per NEC, not sure of the Canadian requirements


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## secutanudu (Mar 15, 2009)

jasonnewyork said:


> secutanudu - not a bad idea to oversize. I plan to run 14-2 UF thru the 1/2" conduit. It's only gonna be 3ft at the most, just to protect the wire as it pops out side of my house and into the ground. Still think I need 3/4"? I guess it's really not a big deal?


For 3 feet it's not much to worry about. I had to pull 3 THWN wires through about 60 feet of conduit with a few elbows...which is why I oversized. Why not do the whole thing in conduit with THWN wires? That's what I did, specifically because the UF wire in the ground got ripped "somewhere". This UF was installed by a previous owner, also about 6" deep. I redid the whole thing in conduit.

If you decide to do it all in conduit, I think you're supposed to put in an expansion joint to prevent cracking (I wish I knew that before I did mine):

Expansion joint info:
http://www.carlon.com/Installation_Training/IT-ISEXPJT.pdf


I pulled a string through the conduit as I glued, then I tied the string tot he wires, and pulled through. Do not run wires through as you glue...the glue can deteriorate the insulation on wires.

Here's how I exited the basement (I exited below grade):


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## Scuba_Dave (Jan 16, 2009)

As noted you must use UF wire for burial
You can run cable in conduit under NEC, the conduit must be larger for the cable
12-3 UF has a diameter of .345" - so 1" conduit is fine
You can run 2 circuits as a MWBC to a detached structure under NEC

To use 12-3 you will have Hot, neutral & ground...then a 2nd hot
Rules have changed on switching a circuit in a detached structure
To have a switch in the house you would need 2 conductors
...1 going to the house...1 going back to the light
So you can have a 2nd circuit in the garage for the lights

Burial depth - 12" if GFCI before it goes in the trench
If you are running a MWBC you would then need a 20a 240v GFCI - expensive
So better to go with the 18" burial depth

I would buy a dual gang GREY PVC box that will attach to the conduit, not blue
At that junction you can then switch to NMB
As I understand you need a switch on each circuit as a shut-off in the garage

Water will usually get into buried PVC, don't worry about it

I would simply run #6 wire for the short distance & put in a 100a sub
Feed it with a 60a 240v breaker
Then wire up whatever you want in the garage

I'd also do the light post in conduit

Be aware many DIY books have had inaccurate information published in them
Some were recalled


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## bobelectric (Mar 3, 2007)

I would of exited the box from the bottom,into 
a 90° eliminate the 2 pulling lls.


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## jasonnewyork (Sep 9, 2009)

Thanks for all the responses... having a difficult time combining them all .

When I say 12/3, I'm referring to NM 12/3 with 2 hots, 1 neutral, and a ground. If I run separate wires, will be 4 in total, sorry if I didn't make that clear.

I have to see what is available in the big box stores, but I will probably end up running NM 12/3 UF through the 1" conduit to the garage. If it's available, I prefer to run 4 12ga THWN wires but not too sure they carry that. 

As for codes, it's my understand that you are allowed to run up to 2 separate branch circuits to a remote structure. Anything greater than 2, a sub panel is required.

In my case, I'm only running one branch cirucit to the garage. The second wire, red, will be the switched lead for the lights on the outside of the garage. I currently have a switch inside my house for the exterior garage lights and plan to keep that.

Wiring wiil be as follows: 12/2 from circuit box for garage power, will meet up with 12/2 from light switch in a j-box in my basement. 12/3 going thru conduit outside also meets at this jbox. Lights and garage will be all one one circuit.


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## secutanudu (Mar 15, 2009)

They sell 12AWG THWN wires at big box stores. All different colors (red/black/green/white).


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