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Nobadays
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# Posted: 18 Nov 2019 16:26 - Edited by: Nobadays
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Okay... I know I should run 10 guage wire intended for solar but I'm trying to go cheap on a little project.
Here's the deal, our satellite internet is on a contract and we have to pay monthly for two years before we can put it on vacation hold. Since we are not at the cabin very frequently in the winter, but would still like to monitor both for security and snow levels our thought is to put up a wifi outdoor camera tied into the satellite internet. Thing is we have lithium storage for our main system so are going to put in a separate solar system just to power the satellite internet and camera. I just scored 2 x 225ah 6v batteries off craigslist ($50 for the pair, 1 year old out of a rich guy's mega motorhome... he change configuration) so I now have the heart of the system.
Here's the question.... the place I need to mount the panel - a spare 245watt, VOC of 37.5, ISC 8.68A - is 30 feet from where the CC and batteries will be housed. I have a bunch of 12/2 Romex, so what are the collective thoughts of runing this Romex from the panel to the Charge Controller? I could put the CC close to the panel and just run the Romex to the batteries from there. (Seems to me the line loss running 12v to the batteries would be more severe. )
Thanks!
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ICC
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# Posted: 18 Nov 2019 17:42
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At a VOC of 37.5, ISC 8.68A the 30 feet of 12 gauge wire will have a maximum voltage drop of 2.89% which is generally considered acceptable, though picky folks like to have less loss than that. The loss will be less when the amp output from the panel is lower though.
To me, the bigger question is whether or not the romex is rated for exterior use? If it is not there is potential danger from the possible deterioration of the insulation.
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Nobadays
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# Posted: 18 Nov 2019 18:00
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ICC... Thank you, kind of what I thought. I didn't think the line loss would be significant... couldn't find the link I had to a loss calculator. Found it after I posted, here is what I got:
Voltage drop: 0.83
Voltage drop percentage: 2.21%
Voltage at the end: 36.67
I also know stranded is preferred for DC voltage but I'm hoping this will see me to spring.
No the Romex is not rated for outdoor usage but this will only be up until May so am thinking that short length of time I won't lose the insulation.
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ICC
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# Posted: 18 Nov 2019 18:26 - Edited by: ICC
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Quoting: Nobadays I also know stranded is preferred for DC voltage but I'm hoping this will see me to spring.
Don't sweat that. It's mostly theory (skin effect) and I doubt anyone's real-life experience will see any measurable difference. Mostly stranded is best used where there is possible wire motion as in a motor vehicle when wires can shake or vibrate. And stranded is easier to bend and curve around stuff. THe main thing to watch for (with non approved for outdoor, is UV deterioration of plastic insulations. Romex is also not rated for use in any conduit, just FYI.
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Nobadays
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# Posted: 18 Nov 2019 19:03
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Thanks ICC! I'll do it right in the spring with proper PV wiring. I just want to get through the winter.
Romex in conduit.... yeh I'm guilty of doing that on a 20' underground run.... pvc is glued and both ends are in enclosed areas where water cannot get into it, but I know the other issue is overheating. The piece of 14/2 in the conduit will only power two things - a transformer to convert AC to DC to run my Shurflo pump, max 10amps and possibly a low wattage 3 watts per ft, 16' = 48 watts) heat tape. I know, not proper and should be replaced with thhn....
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Nate R
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# Posted: 19 Nov 2019 08:14 - Edited by: Nate R
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IF you have a lot of it......You could always do TWO runs of 12ga. Done. 
And, don't forget the panels will rarely be at maximum rated amps.
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Brettny
Member
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# Posted: 19 Nov 2019 08:15
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Water will get in conduit no matter how well its sealed. Movemeny underground almost always happens.
Theres a wire size calculator online too.
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Nobadays
Member
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# Posted: 19 Nov 2019 08:48
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Nate...thought about that but as ICC points out (and I saw after finding my link to the online line loss calculator) the loss will be minimal really. All I will be doing is keeping 2 - 6v, 225ah batteries topped up. The draw will be pretty low with the satellite internet drawing +/- 840watts/day (kil-o-watt meter with usage...camera won't use as much) and the camera much less... like 6 watts/day (read on the interweb, must be true!) A friend near me has 2 old 12v deep cycle batteries that can't be more than 210 - 280ah together fed by 2, 100watt panels and his system keeps up. I think I'll be good, no sweat if I'm not I guess.
Brett.... possibly but that is a broad statement. My trench is on a well drained, rocky hillside with the ground water level about 400' with an average rainfall of around 10-15". Not going to worry too bad about water intrusion.
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CabinBuilder
Admin
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# Posted: 24 Nov 2019 03:25
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FYI
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Nobadays
Member
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# Posted: 24 Nov 2019 08:06
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Thanks CB!
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creeky
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# Posted: 24 Nov 2019 13:36
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I'm guilty of hanging Romex in the air to get solar from one spot to another, I will replace when I bury the line. I should get to that. Ah well. Winter now. Add it to next springs list.
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Nobadays
Member
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# Posted: 24 Nov 2019 14:14
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Got a few of those... to do later tasks, that are still waiting for "later" myself!
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