About to put panels on roof. 5 series of 3. 30v 9 amps each 270watt panels. Will need to run it 80 feet to controller. I take it 8gauge will work it seems do people use higher gauge. Seems gauge would become less flexible for running through conduit pipe
Wire gauge?
- Thread starter wpmaura
- Start date
30v is Vmp?
90 volts for 3 panels
5 x 9 amps is 45 amps
8 AWG is 5% drop
6 AWG is 3% drop
You can change your inputs in the calculator.
Voltage Drop Calculator
This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.
www.calculator.net
A bit on the upper edge on the amperage for #8. Also, do you think you might have a configuration in the future that would exceed 45a?
For cost reduction, look at aluminum wire for the 80' run. That would likely be #4 or #2 Al, but I didn't check.
For cost reduction, look at aluminum wire for the 80' run. That would likely be #4 or #2 Al, but I didn't check.
No that's the max configuration. For that array. Dont have easy acess to 6gauge. Coule double up on the 8 gauge
8 AWG is 5% drop.
Did you play with the calculator?
It has an option to have 2 conductors in parallel which gives 2.5% drop with 80 feet of 8 awg.
Are you borrowing the wire from work?
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Can you order from Amazon or similar? I've bought NM and UF wire several times this way. E.g. here is NM-B "simpull" wire, 100' of 6/2:
Doubling the #8 to give approximately a #6 equivalent is valid, but I don't know if local codes would allow that. The problem with that technique isn't the new equivalent capacity, it's not knowing in the future if one of the two wires has failed.
100' 6/2 ROMEX NM-B (Indoor Cable) Simpull SOUTHWIRE Non-Metallic: Amazon.com: Tools & Home Improvement
100' 6/2 ROMEX NM-B (Indoor Cable) Simpull SOUTHWIRE Non-Metallic: Amazon.com: Tools & Home Improvement
www.amazon.com
Doubling the #8 to give approximately a #6 equivalent is valid, but I don't know if local codes would allow that. The problem with that technique isn't the new equivalent capacity, it's not knowing in the future if one of the two wires has failed.
For reference, 100' of direct burial #4 aluminum (no conduit needed), 3 conductors is $122:
Harsh sardonic reply... best to kindly remind the OP he left out info.
Now I remember your previous posts and that you are in the Bahamas recovering from a hurricane so you cant order from Amazon but you can't be bothered to mention that fact again.
Actually you should be at 2% voltage drop so its a 3% difference from 5% drop using the 8 AWG you have.
8 AWG to 4 AWG.
I see you can write more than a few words but keep asking new questions with none of the info that might be helpful included from your previous posts here where you got good advice.
So what the hell you are in the Bahamas so can probably run any kind of wire you want and who cares if it heats up wasting some power. You are actually going to run the 80 feet of wire in conduit? Dunno how hot your 8 AWG wire will get being undersized but you can do your own experiment instead of relying on established electric codes.
Its not a 2% difference but I get what you mean.
Voltage drop can effect the proper functioning of some electronics, <3% is the defacto standard (and the actual standard in the marine world), but I don't think there is anything magic about that number, many people shoot for 2% or 1%, and for less critical or more foregiving loads 5% or 10% are sometimes permissible.
There are smarter/more informed people than me who can address how important voltage drop is a for a charge controller, so I'll leave that to them.
But there is another reason you want to use adequately sized wire, power loss. If I understand your situation correctly you have a 45A charge current and a 160ft round trip distance from the PV array to the controller and back.
The formula for calculating power loss is P(loss)=I^2R, or in plain english power loss = current squared x resistance of the wire
At 8 AWG: P(loss) = 45^2 x .00062 x 160 = 200W loss
At 6 AWG: P(loss) = 45^2 x .00040 x 160 = 130W loss
At 4 AWG: P(loss) = 45^2 x .00062 x 160 = 77W loss
If I've done the math right (and I'm still learning so don't trust me), with 8 AWG you are losing about 1 kilowatt-hour of energy every 5 hours
The other thing is you are potentially pushing the ampacity rating of your wire (depending on the insulation temperature, and the conditions).
ok, sorry for not posting my life story everyday, but supplies tough, and I dont care about efficiency at the moment as much as I do safety, so if 8 gauge will work but I loose more so be it. Take in mind i have done none of electrical actually had people do this for me and they recomended it was ok, but something about it seemed wrong.
In 2 months I can swap to 6 gauge once utilkty room repaired.
Thanks for you help though.
In 2 months I can swap to 6 gauge once utilkty room repaired.
Thanks for you help though.
I don't know what your local electrical code says, but if efficiency doesn't matter, and your electrical code permits it, then I don't see an issue. You are right at the limit by U.S. standards.
Your in for info you probably dont want to know. Our code just got upgraded to canadas 2 years ago, no idea why. But they only inspect your house when you go to get main power put in that is it. I am living in dorian aftermath, they still dont have the sub cable to cross the ocean they forgot to order it, and just finishing up transformers and stringing poles now. so as long as I dont connect to main power they dont care what I do.
But lets say I do. Then it gets fun, because if my house is 3 years old, that meant all the wires in the house were black and red, now there black in white, if you want to get connected back to main power you have to re wire your house. Lets just say lots of bribes going out there. When I built mine, my plans were aproved by aproval boards signed off, we have a bathroom with a washer dryer in it. The electrical inspector(only one for a country of 400k and that see millions of tourists) failed us because if you look in the dictionary and look up defination of bathroom and it doesnt say anything about a washer dryer. behind the wash dryer alcove in my house is the pantry, it took everything I had to not be a smart ass and say whats the defination of pantry say. Thats where he told us to stick the washer dryer, take in mind I know for a fact he aproved this same design many many times. He just wanted some "lunch money".
Anyway thanks again for the help.
Swap to 4 gauge is 2% voltage drop.
Saying you are in the Bahamas is a short story.
Hope you get it all wired up and powering your house soon.
What does sardonic mean? Lolz
John Frum
Tell me your problems
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I just ran the numbers with https://baymarinesupply.com/bosns_corner_wire_sizes
9 amps
160 feet round trip
30 volts
8 awg is right on the edge with 3.1% voltage drop.
2x 8 awg is equivalent to 5 awg which would be more than adequate.
9 amps
160 feet round trip
30 volts
8 awg is right on the edge with 3.1% voltage drop.
2x 8 awg is equivalent to 5 awg which would be more than adequate.
Where do you get 9 amps from?
He has 5 sets of 3 series connected panels.
Thats 15 panels total.
5 x 9 amps = 45 amps.
Important to be aware that Bay marine (and most marine calculators) assume 105*C rated wire, this is common with marine wire, but not standard for non-marine wire. This won't affect voltage drop, but will affect the amperage that the wire can safely carry. If OP is using wire on hand, its unlikely to be marine grade wire, OP would be smart to check the wire temperature rating before moving forward.
Its also 90 volts for 3 panels in series.
Also not 30V ? You may need second cup of coffee today Joey ?
3S5P
panel specs 30V Voc, 9A Isc
array specs 90V Voc, 45A Isc
