Combiner to Classic Wire Size

tons001

Sorry for asking again but I can't find a wire size calculator I like. I have approximately 100' between my array and my classic. I have already buried the 1.25" conduit and ran #4 wire through it. This was fine when I was planning to run 115vdc 10.12a through it to my classic ... in fact it was probably overkill but I don't want stuff to over heat and my voltage loss was like .30%. After reading this forum for months now, it would appear that I want to bring my array voltage down closer to my battery bank voltage which is 24v. I can rewire my array to give me a total VOC of 66.75v, VMP of 53.40v and a rated array amperage of 20.24. Can my #4 wiring safely handle this or should I take the system voltage back up and run the classic less efficiently?

Thanks for any advice. This forum is hugely helpful.

NorthGuy

Re: Combiner to Classic Wire Size

At 100' (200' back and forth), 50V and 900W array, your losses at full power are going to be 16W with #4 wire - 1.8%.

At 50% production (450W), your losses will be 4W - 0.9%.

vtmaps

Re: Combiner to Classic Wire Size

tons001 wrote: »

Can my #4 wiring safely handle this or should I take the system voltage back up and run the classic less efficiently?

NorthGuy's numbers are very close to what I calculate. Safety is about ampacity, and #4 wire is nowhere near its limits with 20 amps. As far as efficiency is concerned, you are doing the right thing to bring down the Vmp... you may lose a bit more in the cable, but you will gain it back in the classic and the classic will last longer by running cooler.

--vtMaps

tons001

Re: Combiner to Classic Wire Size

Thanks everyone! I am getting a few answers over at MN forum that are in line with these as well. I just wanted to make sure I stay safe and don't lose to much voltage or cause heat in my lines.

niel

Re: Combiner to Classic Wire Size

you should be fine either way as the classic would certainly not be over burdened in any case as you have roughly a kw of pv to work with.

vtmaps

Re: Combiner to Classic Wire Size

tons001 wrote: »

Thanks everyone! I am getting a few answers over at MN forum that are in line with these as well. I just wanted to make sure I stay safe and don't lose to much voltage or cause heat in my lines.

Do not worry about heat in your lines... the ampacity ratings of the wire are all about heat in the lines. Save your worrying for heat in the Classic.

--vtMaps