Running 12-2 wire through conduit ABOVE ground?

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Old 05-15-17, 09:27 AM
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Running 12-2 wire through conduit ABOVE ground?

Hi,

I want to add another circuit to a server room I have. My home was built in the early 1900s in a "cottage" style. Meaning, the house isn't entirely accessible through the unfinished basement.

I was thinking of adding a 20 amp circuit to my server room by running an exterior rated 12-2 wire through a PVC conduit from by unfinished basement, through the outside of the house, right into the room (which is on an exterior wall).


I am unable to dig to bury the wire because the house is built on top of ledge, and there is no dirt to dig. I am also unable to run the wire through the attic because the room has a flat roof.


What would I need to do in order to run this 12-2 wire through the outside of my house, into the room and be NEC compliant and safe?
 
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Old 05-15-17, 11:00 AM
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What you want to do is code compliant but it is easier to pull individual conductors such as THWN through conduit.

One way to do this is mount a single gang weatherproof box on the outside of the house where your wiring exits the house and where it reenters. Run THWN in conduit between those boxes. Inside run NM-b cable through the wall and into the back of the boxes.
 
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Old 05-15-17, 11:11 AM
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Thanks for the reply ray.

Do I need to do anything special to the conduit? Do I need to seal it with PVC glue or not? What size conduit?

If I am understanding your suggestion correctly, I would run THWN wire from the breaker box, to an exterior waterproof box on the outside of the house. Then from there, run normal ROMEX wire to the inside where it'll terminate in a normal receptacle?
 
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Old 05-15-17, 11:31 AM
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Individual conductors need to be run in a conduit or raceway.

For a 20 amp circuit using 3 #12 wires you could use 1/2" PVC conduit. The joints will be glued.
 
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Old 05-15-17, 11:41 AM
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Regular NM-b (Romex) is not allowed outside in conduit. Outside conduit is considered a wet location. THHN/THWN is approved for wet locations.
 
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Old 05-15-17, 11:43 AM
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There are a few possible options, some of which depend on what your municipality allows. There are special connectors required for each option. It's not a huge deal but you can fail an inspection if you don't know about "one tiny part". Not fun.

Since this is a new circuit and you live in MASS (2017 code adoption for 2017), it is likely that you will need to have an ARC Fault breaker (ACFI) - if you wish to be code compliant. If this will be inspected, you will likely fail without one. You can get ACFI breakers for less on eBay. I've gotten them for $15-25 (instead of $35-45).

1. MC cable (the wires are already inside flexible metal conduit). All connections MUST be made inside the house. The armored housing also must be grounded.

2. A better option perhaps is UF cable. I suspect this might be your best way to go, if its approved for your area (non-metallic sheathing).

3. Running wires through a combination of stiff and flexible plastic conduit. Time consuming and a pain. I'd elect option 1 or 2 - whatever is permitted for your area.

Good luck!
 
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Old 05-15-17, 11:56 AM
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1. MC cable (the wires are already inside flexible metal conduit). All connections MUST be made inside the house. The armored housing also must be grounded.
The OP is asking about running cable outside. MC is metal clad and can't be used outside.
 
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Old 05-15-17, 12:26 PM
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I meant the PVC Jacketed version of MC - thank you for catching that.
 
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Old 05-15-17, 05:34 PM
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Hi Jefferson17,

You are correct, ARC Fault breakers are needed in MA. I was going to grab some UF wire (https://www.lowes.com/pd/50-ft-12-2-...e-Roll/1098053)

and some PVC conduit. My remaining question is what is the best way to "terminate" the circuit. What is the recommended approach to going from the conduit, to the inside of the house where it'll terminate in the receptacle?
 
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Old 05-15-17, 06:39 PM
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I was going to grab some UF wire
As I stated individual conductors would be easier to pull.
What is the recommended approach to going from the conduit, to the inside of the house
As I wrote:
One way to do this is mount a single gang weatherproof box on the outside of the house where your wiring exits the house and where it reenters. Run THWN in conduit between those boxes. Inside run NM-b cable through the wall and into the back of the boxes.
 
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Old 05-15-17, 07:48 PM
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>> You are correct, ARC Fault breakers are needed in MA. I was going to grab some UF wire (https://www.lowes.com/pd/50-ft-12-2-...e-Roll/1098053)


IF (and If is the big question) the PVC jacketed version of MC is allowable for exterior use (terminated appropriately), that would be my first choice - as it is simply ONE major solution and there would be no conduit run. You may wish to call your town's inspector / code official - they are usually pretty helpful.

You may also wish to consider Ray's suggestion for THHN. I did some looking and can't find good prices on THWN, but the THHN seems pretty reasonable - assuming it's allowed inside conduit for that application. It seems logical to me that it would be ok but validate this with Ray and a local inspector, etc. I have not used that cable type before.

Home Depot sells a version of THHN that has all the conductors you need, in one roll without buying separate colors then combining them afterward. I looked at the Lowes site and didn't see the equivalent. Here's what I found there:

Multiple Choices
3 - Building Wire - Wire -

One specific 50' option
Cerrowire 50 ft. 12-3 Black, White and Green Cabled Solid THHN Cable-112-161253B - The Home Depot

FYI - if you do need to have "fun with conduit", a nice trick for pulling/pushing wire through conduit is "soaping up" the wires first w/ Dawn etc. They do make "special liquid" for this but dish soap works really well.

>> My remaining question is what is the best way to "terminate" the circuit. What is the recommended approach to going from the conduit, to the inside of the house where it'll terminate in the receptacle?

I will defer to others to provide a better response - some of this is likely specific to to the type of conduit, cable, etc. I've worked a bit w/ Romex connectors etc but I have LIMITED conduit experience. In my experience, the Home Depot electrical guys are actually pretty good. Your mileage may vary. At least if you buy stuff you don't need it's easy to return it for a refund.
 
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