USE or UF cable transition to romex for solar panel array

[mikael6]

I am planning on installing a small solar panel array (4-6 250 watt panels) outside on the ground most likely using a ballast ground mount system (like ecofoot2). I plan on using USE or UF cable running from panels to conduit going under ground (only distance of about 5 feet) from solar panel array and then coming up out of ground in pvc conduit next to side of house into an LB junction box and then small section of conduit through house wall to basement. I'd like to transition in the junction box outside from the USE or UF or THWN to romex and then romex through basement above drop ceiling (not in conduit) to the dc disconnect. The run in the basement will be about 35 feet. I'd like to avoid the hassle of running conduit in the basement if possible as I know thhn must be in conduit.

Questions:

Will this work?
Are there any issues doing this (breaking codes, etc)?
Is there a better way?

[Naptown]

If you run DC inside the house you will need a disconnect where it comes in the wall and all wiring to the inverter will need to be in metallic raceway or pipe, Marked every 10 feet that it is DC.
If possible Mount the Inverter at the point of entry then you can use romex from there if the AHJ allows it. Remember that the AHJ has final say and there is a lot of differing interpretations as to what you can do from inspector to inspector.

[mikael6]

Ok, so it sounds like this might be a better option for me:

Use USE or UF cable running from panels to conduit going under ground (only distance of about 5 feet) from solar panel array and then coming up out of ground in pvc conduit next to side of house into an LB junction box and then small section of flexible conduit through house wall to basement to dc disconnect box nearby. Then flexible conduit from dc disconnect to inverter that I locate nearby. Then long run of romex through basement and outside the house again to an AC disconnect box located near the electric meter (not sure if it matters that the AC disconnect be located near the electric meter and where the electric service from the street enters the house; I know that the AC disconnect must be outside per utility company rules) . Then from AC disconnect back inside to a breaker in the electric service panel located near by.

The reason I want to do it this way is twofold: 1. The area outside where I want to locate the panels is on the other side of the house from where the electric service panel is. I want to avoid having to trench up the whole yard to run the wiring carrying the DC current to the location outside the house where the electric service panel is. 2. I want to avoid having to run conduit inside the basement for the wiring as it will be a lot of work.

Let me know hour thoughts.


I will check with AHJ of course.

[Zee]

Given the desire for romex in basement and the economies of scale at a small system size, consider ac panels . Romex can easily be used under house. DC disconnects no problem.

Also , at array, consider PV wire. Thicker, heavier duty. . Otherwise definitely use USE-2 , not UF.
(unless UF meets all the sunlight and wet condition ratings,
weather seriously degrades even the best insulation,
i have never seen or used UF in 12 years of PV installation)

[Sunking]

Romex can easily be used under house. DC disconnects no problem.

NM for solar?

[mikael6]

I considered panels with micro inverters but I already have a sunnyboy 700u inverter that I got a good deal on that I want to use. So, this will be cheaper than using the microinverters. I may add more panels in the future so the array may expand. I guess that the main questions are whether I can use romex (12-2 or 10-2 with ground) in the basement co carry the current from the inverter to the ac disconnect and then panel. And, the location of the AC disconnect as to where it must be located. I know it must be located outside per utility company regulation, I am just not sure it it needs to be located outside the house near the inverter or outside the house on the other side where the electrical service panel and meter are.

[Naptown]

NM for solar?

From the inverter to the panel it is legal. Not for DC however.

[Sunking]

From the inverter to the panel it is legal. Not for DC however.

Yes I realize that now. Being on the commercial/industrial side we do not have the luxury of using NM.

[Naptown]

And very few AHJ's allow me to use it either. Pipe outside and MC inside.

[Sunking]

And very few AHJ's allow me to use it either.

Well we know who is right then huh?

I am not a fan of NM. I did not use it on the last two homes I built for myself. Plumbed and piped all of it with THHN.

[Naptown]

Well we know who is right then huh?

I am not a fan of NM. I did not use it on the last two homes I built for myself. Plumbed and piped all of it with THHN.

How does the water flow out of the wires?

Actually NM uses thhn insulated conductors. And if I remember correctly your house is ICF.

[Sunking]

Actually NM uses thhn insulated conductors. And if I remember correctly your house is ICF.

Correct on both accounts. Myself and an EC who is my friend did the electrical. On the interior envelope (outside walls) I installed 2 x 4 steel studs on traditional 24 inch centers. We then piped in both electrical and Data/Communications. Once that was in placed foamed in the cavity and sheet rocked using a product called QuiteRock. Interior walls are 2 x 6 steel studs using standard glass mats and QuiteRock sheathing.

Next house if I get a chance will likely be about the same. Costa Rica is out, and now Panama is looking good.

[Naptown]

So 2 candles to heat and a bag of ice a day for cooling?
No smilies on the iPhone.

[Sunking]

So 2 candles to heat and a bag of ice a day for cooling?

You got it my friend. Even have zoned cooling and heating. Not too mention WW-III could be going on outside and I would not hear it.

[Naptown]

What insane R factor are the exterior walls ?