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paulz
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# Posted: 9 Nov 2021 09:40am
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I'm jockying around my arrays, it's good exercise. I have a chance to buy a 500ft. spool of 6awg cable for $150. Would this work ok?
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paulz
Member
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# Posted: 9 Nov 2021 10:13am
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Never mind. I see THHN is not approved for solar. Bummer.
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gcrank1
Member
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# Posted: 9 Nov 2021 10:31am
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Inquiring minds, and all that.....
Not approved for solar, as in, not for commercially installed applications, or, not safe, what?
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paulz
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# Posted: 9 Nov 2021 10:41am
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Good question, hoping Brett ICC or Steve will pipe up. For one thing though, it has to be in conduit if outside, which of course, PV cabling is.
Oddly, the 30 panels I have that came off a big house, and was a professionally installed system, had this exact wire, in conduit.
But all the solar sites say only PV or USE wire is approved for solar.
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FishHog
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# Posted: 9 Nov 2021 10:47am
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I'd use it, thats a good price. In a conduit, can't see it being an issue, but make sure its all covered, as many times some is exposed to sun and I suspect that is the issue.
I don't think solar generated electricity cares what type of copper wire it travels through, so it has to be the elements its exposed to that is the potential issue.
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ICC
Member
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# Posted: 9 Nov 2021 11:06am - Edited by: ICC
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The insulation on THHN is not UV resistant. The outside layer gets brittle and flakes off.
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paulz
Member
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# Posted: 9 Nov 2021 11:30am
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Thanks guys. I do have all the conduit that came off that house roof...
Also, MC4 connectors only take 10awg I think. So if you have a long run from panels to cabin, and a lot of potential amperage, do you transition to different connections and bigger wire?
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travellerw
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# Posted: 9 Nov 2021 12:35pm
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As far as I know.. THHN wiring is fine for solar as long as its used within its rating..
So, THHN used in dry, indoor locations. So you could use it to run from a roof install down through walls to controllers. It can be used in conduit, but not if there is risk of moisture (like buried).
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travellerw
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# Posted: 9 Nov 2021 12:56pm
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Quoting: paulz Also, MC4 connectors only take 10awg I think. So if you have a long run from panels to cabin, and a lot of potential amperage, do you transition to different connections and bigger wire?
%100 yes.. You can find Ampacity calculators online. They will help you determine the gauge of wire you require based on the voltage and amperage of the system. Personally I shoot for a %3 lose but that can get expensive on a long run with low voltage and high amperage.
Ebay used to have MC-4 connectors for 8 AWG. However, I have bad experience with cheap offshore connectors. I have found many that were so hot you couldn't touch them.
In really big wire installations (like 6awg), I used terminal blocks in weatherproof housings with ring connectors (anti corrosion paste too).
Renogy has a decent cable size calculator.
https://www.renogy.com/calculators#tab_solar-cable
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ICC
Member
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# Posted: 9 Nov 2021 01:32pm - Edited by: ICC
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Quoting: travellerw It can be used in conduit, but not if there is risk of moisture (like buried).
That is a good reminder... I forgot something.
Depending on how the NEC is interpreted any conduit in an outside location is considered a wet location. Our inspector here looks at conduit fittings as possible water entry points. That is especially true of some types of conduit and if sloppy installation has occurred.
There is THWN which is the type made for wet locations. Now I remember that is why we always ran the dual purpose wire, rated THHN/THWN in conduit. I believe there is a difference in maximum rated temperature though which is why plain THHN is made.
I did not read the label before as I was on my phone in a hurry. I see that is rated THWN-2 as well as THHN so conduit is fine. The -2 indicates a higher temperature rating.
It is green though so according to the rule book it is only to be used for grounds. If nobody is looking then all you need to worry about is forgetting what you did yourself or some other person in the future assuming green is ground and possibly hurting themselves or something along those lines.
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paulz
Member
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# Posted: 9 Nov 2021 02:20pm
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OK for proper outside, non conduit runs from array to SCC you need USE cable, I don't see PV cable in 6awg. Not seeing much USE-6 either. According to the online calculator I do need 6 minimum. And it looks like about a buck a foot. 500 ft. of that THHN looks pretty good for $150.
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NorthRick
Member
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# Posted: 9 Nov 2021 03:36pm
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Quoting: paulz OK for proper outside, non conduit runs from array to SCC you need USE cable, I don't see PV cable in 6awg. Not seeing much USE-6 either. According to the online calculator I do need 6 minimum. And it looks like about a buck a foot. 500 ft. of that THHN looks pretty good for $150.
As ICC pointed out, that wire is also rated THWN-2.
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paulz
Member
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# Posted: 9 Nov 2021 03:57pm
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Told him I'll take it. I should put it in conduit anyway.
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Steve_S
Member
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# Posted: 9 Nov 2021 05:15pm
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All of my PV Wire is Exterior Grade as provided by my primary supplier.
Direct Link to Southwire Product.
http://industrial.southwire.com/en/tile/22/cable/20459/?country=CA
As my racking has channels the wires run within, then I used PVC Boxes & Conduit to bring it all down to combiner.. Combiner @ Rack to Powerhouse is also all in PVC Conduit underground.
*NB: There are 3rd party Wire Channels & Clips available for cable management on racking & equipment.
** Warning: The wires are NOT Abrasion proof, be aware of routing near "sharps" and edges and to affix wiring to prevent rubbing of chaffing. EVEN CLEAN / CHAMFER inside Conduit edges! Not a Joke !! ALSO be aware that an open conduit end is an invitation to some nasty stinging bugs. Lessons Learned Dept !
Rack & Panel ground uses 6AWG Stranded Copper Green Sheathed Ground Wire that is terminated to a Grounding Plate 30" deep and 3' from Sea Can (that code here).
Link to Southwire Ground Wire.
http://industrial.southwire.com/en/tile/5/spec/44067/?country=US
AS ALWAYS: Refer to the Electrical Code(s) relative to your location.
Hope it helps, Good Luck.
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paulz
Member
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# Posted: 9 Nov 2021 06:54pm - Edited by: paulz
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Well I'm back from the big city. And I don't have to worry about polarity. He had two spools, I got them both.
I've scouted out a spot with the best unshaded southern exposure. It'll be abut a 100' run from the cabin. I should have enough conduit already to make it. Previously I've been placing them on and around the cabin due to wire length restrictions, in not ideal locations.
Thanks for the help guys.
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Brettny
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# Posted: 10 Nov 2021 06:34am
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Quoting: ICC The insulation on THHN is not UV resistant. The outside layer gets brittle and flakes off
This is my understanding as well. You can use it In conduit up to the roof. You can then use a junction box to connect the solar cabling to.
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paulz
Member
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# Posted: 17 Nov 2021 06:44pm
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Been playing around with this online calculator. In the 'array optimum operating voltage field', if I enter 100, which is what I measure disconnected, I get 8awg. However, in the shade these days, hooked up, the SCC only reads about 25v. If I put that in the field is tells me much thicker, like 2awg.
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travellerw
Member
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# Posted: 17 Nov 2021 07:14pm
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Quoting: paulz Been playing around with this online calculator. In the 'array optimum operating voltage field', if I enter 100, which is what I measure disconnected, I get 8awg. However, in the shade these days, hooked up, the SCC only reads about 25v. If I put that in the field is tells me much thicker, like 2awg.
In a cloudy situation, the AMPs will also drop..
Use the max V and A values on the back of the panel.
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Nate R
Member
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# Posted: 17 Nov 2021 08:02pm
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optimum voltage is NOT the disconnected voltage at all.
What panels do you have? How many? Parallel or series? Any sticker pics or info on them?
How far a run?
You also should keep in mind that your panels likely won't be at max amps 95% of the time.
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paulz
Member
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# Posted: 18 Nov 2021 11:22am
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My panels are 31v vmpp. I run 3 in series, I just rounded up to 100 for the calculator.
As trav said, the amps goes down with the clouds (trees, fog in my case) so I'll just go with then 100. The 6awg wire I bought is more than adequate according to the calculator.
Thanks guys.
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