PV wire vs. THWN

[astrofisher]

Google search can be frustrating. I'm doing a small solar project (my first) and am getting ready to mount a couple of ground mount panels and run wire to my small tool shed. I have a few rolls of 10AWG THWN wire and was thinking about using that in conduit from a PV disconnect to the shed. The first result Google listed:


Then — the very next sentence: "THHN wire has a small insulating layer on the conductor, and that insulation is fine for lower voltage solar panel setups."

And then: "This could cause some problems, though. The solar panel voltage is around 15 volts, but the power company’s grid has 120 or 240 volts of alternating current."

Anyway, back to my query. In a similar situation to mine, is it common practice to switch to THWN and run in conduit back to the building?

 

[yabert]

I will look at answer from other as I'm also interest to know.
One point of PV wire is probably sun / UV rated.

 

[SunDave]

99% sure you are good to go. My 400+ volt arrays run through THHN/THWN dual rated cable. It is rated to 600V. The electrical inspectors in this area said the wire does not necessarily de-rate for DC, but all the switch gear does.

The confusion in the web search is likely about using it as interconnects for panels, vs. running DC feeders in conduit. The DC run really has nothing to do with "solar" or "solar panels". It is just a DC run at a certain voltage and amperage.

Also, I just noticed your search result says THNN. That's enough of a reason not to trust it right there!

Good luck with your project.

Yabert, you are spot on as well. The sun\UV rating, and the fact that it is more accessible has a lot to do with using the PV rated cable for inter-connecting panels.

 

[Mattb4]

Google search can be frustrating. I'm doing a small solar project (my first) and am getting ready to mount a couple of ground mount panels and run wire to my small tool shed. I have a few rolls of 10AWG THWN wire and was thinking about using that in conduit from a PV disconnect to the shed.

...

Yes you can run THWN wire in conduit. Just be aware of maximum amperage limits. It is not rated for outdoor exposure or direct burial.

 

[Bluedog225]

Edit-I didn’t notice you were running it in conduit.

If you hold quality PV wire and thhn/thwn, you will see the the PV wire has a different insulation type.

People here have reported decades of use with quality PV wire that has not visibly degraded in the sun.

While I don’t have any test data, I believe a quality PV wire will outlast the other in an exposed location.

Also, if you search this form, and get to know some of the more reliable members, I believe you’ll find they recommend dedicated PV wire. I often also see the recommendation to source it from a United States manufacturer.

These days are general Google search is not to be trusted.

 

[rogerheflin]

Google search can be frustrating. I'm doing a small solar project (my first) and am getting ready to mount a couple of ground mount panels and run wire to my small tool shed. I have a few rolls of 10AWG THWN wire and was thinking about using that in conduit from a PV disconnect to the shed. The first result Google listed:
View attachment 252801

Then — the very next sentence: "THHN wire has a small insulating layer on the conductor, and that insulation is fine for lower voltage solar panel setups."

And then: "This could cause some problems, though. The solar panel voltage is around 15 volts, but the power company’s grid has 120 or 240 volts of alternating current."

Anyway, back to my query. In a similar situation to mine, is it common practice to switch to THWN and run in conduit back to the building?

The above info is like all AI picked info, almost always complete garbage. Googles AI picked answers and their "non-AI" suggested answers are typically very unreliable--I read them because it is amusing to see how bad they really are. "panel voltage is around 15V"--maybe that is true for a garbage 50w panel, but none of the larger ones are as low as 15v/panel. What they are saying only holds true if you don't wire more than one panel together, and for a system of any size no one uses a single panel connected to a MPPT except when using micro-inverters and in that case the DC wire is never going very far. Wire 3 panels together and you are up to 120-150V. Note I am typically NEVER finding a useful result in the first few google results. The higher up on the first page it is , the less likely it is useful, and often if you were to believe the first few results and follow it then it is likely a NEGATIVE-value result that will cause you to do something wrong and possibly cost you money.

These days are general Google search is not to be trusted.

Google search is rapidly going backwards. Give it enough time and they will be sucking as bad as the other useless search engines, and there will be a chance that someone can beat them.

 

[SparkyJJO]

That is the most absurd thing I've read today.

 

[ricardocello]

The above info is like all AI picked info, almost always complete garbage

It's funny, as soon as I read the post, I thought "Stupid AI".
I'm now realizing that I've changed my mental information processing to just assume AI is making up crap when I search.
Wasn't that way a year ago. Stupid AI.

 

[SparkyJJO]

It's funny, as soon as I read the post, I thought "Stupid AI".
I'm now realizing that I've changed my mental information processing to just assume AI is making up crap when I search.
Wasn't that way a year ago. Stupid AI.

It is called garbage in = garbage out

Current "AI" isn't smart. It just regurgitates stuff in a easier to read format. Still garbage.

 

[ricardocello]

OP: You can use THHN/THWN2 in conduit for a ground mount, as long as both ends terminate inside of junction boxes.
Any outdoor exposed wire going to the panels should be PV wire.
Don't forget to run a ground wire (green or bare) to the panels to ground the frames.

 

[summit]

Google search can be frustrating. I'm doing a small solar project (my first) and am getting ready to mount a couple of ground mount panels and run wire to my small tool shed. I have a few rolls of 10AWG THWN wire and was thinking about using that in conduit from a PV disconnect to the shed. The first result Google listed:
View attachment 252801

Then — the very next sentence: "THHN wire has a small insulating layer on the conductor, and that insulation is fine for lower voltage solar panel setups."

And then: "This could cause some problems, though. The solar panel voltage is around 15 volts, but the power company’s grid has 120 or 240 volts of alternating current."

wow, completely incorrect, AI alert! there is no thinking involved, just regurgitation

 

[Gadwall*Drake]

Imitation Intelligence strikes again.

 

[astrofisher]

OP: You can use THHN/THWN2 in conduit for a ground mount, as long as both ends terminate inside of junction boxes.
Any outdoor exposed wire going to the panels should be PV wire.
Don't forget to run a ground wire (green or bare) to the panels to ground the frames.

That's the plan. I'll have a box on each end. PV wire connecting to the THWN in the box at panels. A ground wire will run back and connect straight to the existing ground rod.

 

[astrofisher]

I will look at answer from other as I'm also interest to know.
One point of PV wire is probably sun / UV rated.

Yes, the THWN wouldn't be exposed. PV wire to a box then THWN in conduit back to shed.

 

[cdsolar]

I ran PV wire from Windy Nation from my panels to my combiner box at my ground mount. As I was young and inexperienced, I also ran PV wire in my underground conduit to my side of building disconnect. THWN would be fine underground.

I did 8 instead of 10 awg underground to reduce voltage drop.

 

[Mike 134]

Google search can be frustrating. I'm doing a small solar project (my first) and am getting ready to mount a couple of ground mount panels and run wire to my small tool shed. I have a few rolls of 10AWG THWN wire and was thinking about using that in conduit from a PV disconnect to the shed. The first result Google listed:
View attachment 252801

Then — the very next sentence: "THHN wire has a small insulating layer on the conductor, and that insulation is fine for lower voltage solar panel setups."

And then: "This could cause some problems, though. The solar panel voltage is around 15 volts, but the power company’s grid has 120 or 240 volts of alternating current."

Anyway, back to my query. In a similar situation to mine, is it common practice to switch to THWN and run in conduit back to the building?

Wow what a totally BS google answer. Yes you can run THHN back to the shed underground. The THHN will have a dual rating on the jacket THHN/THWN so it can be used in wet locations. 10Ga will be fine since you're only connecting 10 panels or so.

 

[robbob2112]

I ran PV wire from Windy Nation from my panels to my combiner box at my ground mount. As I was young and inexperienced, I also ran PV wire in my underground conduit to my side of building disconnect. THWN would be fine underground.

I did 8 instead of 10 awg underground to reduce voltage drop.

I bet that was a hard pull with larger wire and the extra thick PV insulation that usually adds 2 sizes..your 8awg was probably more like the diameter of 4awg. Especially if you used the fill chart based on the awg to pick the conduit size.

 

[DPC]

Tw wire is nylon insulated wire
Excellent stuff
Very common

No issues using it on dc 600 volts or less.

 

[cdsolar]

3/4 in conduit. No problems.

 

[jimsloy]

I need to run about 200'. 8S panel setup. Going to use 8awg. 13a, 296vdc, 4000w on one pair. Home Depot THHN or Windy Nation 8awg? It will be underground from array up to garage.

 

[robbob2112]

Just THHN-2 or THWN, it needs to be water resistant in buried conduit. Make sure to running an EGC (equipment ground conductor) along with the other wires to use on grounding the panel frames and anything else metal at the array. Don't drive a ground rod at the array.

Use a voltage drop calculator to see how much you will loose due to distance. Since you aren't trying to run tools directly off it the loss is just wasted power so no limits on it, just get an idea if up sizing is worth the cost.

Voltage Drop Calculator | Southwire

www.southwire.com

Do make sure to use a SPD at the array and at the house...that long run is a great antenna and the SPD should prevent your equipment from getting fried. Also I would recommend an IMO dc isolator at the house and array. If you choose only one place it goes just before the wires enter the house. And that gives you someplace to mount the SPD.

 

[yabert]

Going to use 8awg

Interesting. The voltage drop at only 13A over 200' is around 2% for 10AWG.
So, personally I would use 10 instead of 8, but other peoples maybe have specific advise.

 

[jimsloy]

Voltage Drop meter on order from Amzn - should be here today. Thanks on the THWN recommendation - I'll stick w/ that. I am planning to get IMO disconnect for the house side - so i need the same thing at the array side? Does the SPD go on the 'outside' ends of the IMOs or 'inside'?

 

[robbob2112]

The SPD goes on the outside - before house entry as does the DC isolator.

For AC wiring the typical limit is 3% - but for solar DC it just means you get slightly less power at the MPPT.

The round trip is 400ft...
I'd probably accept the drop and use 10awg myself, but if you ever intend to add more panels at the array pulling 8awg is probably worth it.

Stranded THWN/THHN-2 ....

The only reason for a disconnect at the array is so you can work on something out there without having to walk back to the house to shut it down. Kind of a pain to notice a wire hanging and have to walk back to the house to turn it off, then reclip/tuck it, then back to the house to turn it back on. A careful person never touches anything out there unless the switch is flipped - and even then the panels are still generating so you take care.

If you have an AIO they can sometimes backfeed an AC voltage on the DC lines is why you don't touch things at the array without killing the power.

 

[jimsloy]

By "outside" I meant Array-SPD -> DCiso -> 200foot run to house -> DCiso -> SPD -> Unit in House
vs
'inside' meaning Array -> DCIso -> SPD -> 200foot run -> SPD -> DCiso ->Unit in House

Which should I be doing - the 'outside' or 'inside' version?