Conduit questions--Underground PVC to above-ground EMT

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Old 06-18-20, 04:20 PM
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Conduit questions--Underground PVC to above-ground EMT

I am wiring a ground-mount solar system. Plans call for PVC conduit underground and, as I understand it, I need EMT for above ground at the solar panels and up the wall to the attic.

1) I plan to run EMT up the wall to the attic, then run my wiring through the attic to the main panel. Do I need a junction box connecting the PVC to the EMT to ground the EMT? If so, how far above grade does it need to be? Or can I use an adapter from PVC to EMT? I can also ground the EMT in a junction box in the attic.

2) The plans call for 8AWG THWN-2 from the solar array to the panel. Do I need to run the THWN-2 through conduit in the attic? Can I wrap it to create a romex-like bundle? Or I could convert from THWN-2 to 8-3 romex in a junction box and skip the conduit (and risk rats getting to it...)

What is code for PVC-to-EMT and do I need conduit in my attic?



 
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Old 06-18-20, 06:37 PM
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Under the NEC you are allowed to run PVC below and above ground. PVC above ground does tend to get wavy with the temperature changes so running EMT up the wall might be a better plan. I would recommend installing a metal junction box at the point of conversion from EMT to PVC to facilitate proper grounding. The box can be at any level you want. There no codes that apply on an outside wall. For the EMT be sure to use compression raintight fittings. For the PVC be sure to install an equipment grounding conductor.

Anyplace you run conduit you should use THHN/THWN conductors. THHN/THWN conductors are required to be run in conduit. NM-b cables may not be run in a conduit that is installed outside. You may use UF cable in conduit run outside.

Conduit is not required in an attic but cables installed 6' from an access hole will need to be protected by framing or running boards.
 
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Old 06-19-20, 07:28 AM
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I just did a couple of these transitions at my home. Using pvc LB outside wall, short pvc section to threaded adapter inside the wall, then metal/EMT LB on interior wall. Makes for a neat install. My wall was CMU block and this worked well for both a 1/2” system and 1” system. Seal external penetration.
You may need either sch80 for the exposed pvc or at least some protection over sch40. I ripped a size up conduit into a half shell and my inspector was good with that.
 
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Old 06-19-20, 09:00 AM
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Hi, how far from grade to where the pipe enters the attic? PVC does tend warp with temp changes, however that can be limited by using expansion joints, you can also use the PVC underground, stub up above grade then switch over to EMT using the appropriate fittings , no need for a box until you get into the attic, then switch over to cable.
Pulling a ground wire is always a good plan.
Above grade PVC to EMT = PVC male adapter to threaded coupling to compression fitting, or PVC all the way.

Geo
 
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Old 06-19-20, 11:13 AM
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Thanks, guys.

I will run EMT along the wall. I don't think i can get conduit inside the wall.That wall is on the southwest corner, facing west, so it gets afternoon sun.

Another question. I trenched the conduit run originally thinking I would use PVC all the way up the wall. I will use EMT. Attached is a photo of my trench and side wall. I would like to run the EMT conduit

alongside the downspout to hide it a bit. A junction box is the ideal transition, but I would have to mount it above the hose bibb. The electrical box in the photo is an unused landscape lighting stub. Is it code or acceptable practice to run PVC threaded adapter to a water-tight EMT fitting like a Myers hub (it may get messy getting the M/F right) to the EMT?

How would you transition from PVC underground to EMT?
 
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Old 06-19-20, 11:13 AM
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The plans call for 8AWG THWN-2 from the solar array to the panel.
Observation....... as far as I know..... you need a disconnect on the outside of the house between the solar panels and the inverter. You could make that your splice point.
 
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Old 06-19-20, 11:38 AM
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Hi Pete, Yea, that's my understanding and i am trying to sort that out. It is a kit using Enphase micro-inverters so the inverters are on the array instead of DC to the garage. The company that sold the kit said the Enphase micro-inverters automatically shut down when they lose connection with the grid. It is all AC wiring and there is a breaker in the Enphase combiner at the array (it is a ground-mount), plus the breaker in the main panel. The country permit office approved it with no disconnect switch on the SLD. The PE who did the SLD said he is not sure what the county or the POCO require...which doesn't inspire confidence.

A NEMA3 disconnect switch could serve as the transition between PVC and EMT, mounted above the hose bibb. I am a little nervous about anal inspectors because the approved plans are stamped saying any contractor deviations must be approved in writing by the county or it will be rejected. The county has a reputation for being a real pain to work with. I have trouble believing an inspector would reject a disco switch but then again, it's not on the approved SLD

What do you think?
 
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Old 06-19-20, 12:22 PM
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How would you transition from PVC underground to EMT?
Unfortunately, EMT right at grade and just below is the worst case rusting location.
 
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Old 06-19-20, 01:19 PM
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Hi, Was this system designed by Enphase and signed off by the county the I don’t think you should deviate from that, the system is protected at the array , one question I have is what kind of equipment is connected at the other end of these cables , is it at your service entrance?
Geo
 
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Old 06-19-20, 02:06 PM
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The system was designed by an Enphase distributor and signed off by the county

The wiring goes to a sub panel i am installing adjacent to the main panel, which is full.
 
 

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