Solar Panels

I'm replacing my solar panels next weekend and was wondering what type of wire you solar folks use from the panels to your charge controller. I'm using 4-300 watt, 20 volt panels series/paralleled. I'm figuring 10 gauge wire, but what kind. Thanks for your help.

You say youre ".... using 4-300 watt, 20 volt panels series/paralleled."

Is that two in series (40 volts) in parallel with the other two in series???????????

If so that's 1200 watts at 40 volts and using P = E X I, 1200 = 40 X so X in amps = 1200/40 = 30 amps

NO I would NOT use 10 Gauge 30 amp rated wire, but I would use at least 8 Gauge 40 amp rated or even 6 gauge 50 amp rated wire SUBJECT TO AND DEPENDANT UPON THE DISTANCE AND ALLOWABLE VOLTAGE DROP............

NOTE this is the best case max scenario if the sun were bright and direct overhead so its seldom if ever you would actually harvest 1200 watts or 30 amps !!!!!!!!!!!!!!!! but regardless, I would still use bigger then 10 gauge wire for a safety factor, to allow for expansion, and to reduce voltage drop

I would use fine stranded copper wire NOT solid and NOT aluminum

NOTE here's a chart and program to figure the voltage drop to help you decide what size wire to use.

NOTE when considering a wires ampacity it makes a big difference if its a single wire in open air or jacketed conductors or enclosed in conduit conductors and if so how many etc etc SOOOOOOO THE ROUGH ESTIMATED AMPACITY I USED ABOVE MAY BE DIFFERENT SUBJECT TO ALL THESE PLUS A FEW OTHER FACTORS IE 10 Gauge could possibly suffice but Id still likely use at least 8 or even 6 gauge subject to distance and how much voltage drop I'm willing to tolerate

CONSULT THE MANUFACTURERS RECOMMENDATIONS AND USE THEM INSTEAD OF MY OR OTHERTS OPINIONS but still bigger is better to reduce voltage drop and to allow for expansion YOU HAVE TO KNOW THE DISTANCE AND ACTUAL WIRE AMPACITY AND ALLOWABLE VOLTAGE DROP TO ANSWER CORREECTLY

SURE 10 Gauge could "work" but I never exceeded 80% of the rated ampacity which would ONLY be 24 amps in 10 gauge 30 amp wire BUT that's for "max continuous current" and I doubt you will ever get a full 30 amps "continuous" anyway

John T
Voltage Drop Calculator

Great advice as usual John T .

I wish someone would help me put "solar panels" on my farm- I have no clue.

Weather resistant insulation is important.

Any weather resistant copper wire is fine. 10 gauge is kind of small unless your wire run is 30 feet or less. I assume you are wiring for 40 volts. #8 copper is good for 50 feet.

In our area its THE AMISH that are really getting into Solar. Many have 4000 to 6000 watt rooftop or fixed ground mount arrays elevated at 47 degrees facing south of course.

Ifffffffffff your local electricity utility allows grid tie you dont need battery energy storage so much plus inverters BUT some now use net metering so your savings is less grrrrrrrrrrrrrrrr

Economics and payback are NOT the ONLY reason why I may or may not install solar on my next home.......Its NOT for everyone I'm more into TOTAL energy savings and self sustaining and will consider Super Insulation,,,,,,,,,,Perhaps partial in ground construction,,,,,,,,,,,Perhaps PASSIVE solar heating,,,,,,,,,,Perhaps solar hot water heating,,,,,,,,,,,Perhapos some geo thermal

Local utility charges and availability makes a big difference as to an investment in insulation or geo thermal or solar or wind. Just because some like it and some don't is of no consequence to me ITS A PERSONS OWN PERSONAL CHOICE which may or may not prove economically the best........

John T An engineer and believer in alternate energy and I do NOT like to limit my options to only one thing, I consider solar and super insulation and wind and geo thermal and all else lol

I admire your knowledge- nice to hear these things. I have a 50' tower my great Grandparents used in the early 1900's......20' from my back door- nothing on top. They used it with a "wind generator " back then because the rural areas didn't have "electricity" till after the war; with I could do something with that! Also- I have had our local electric-plumbing company give me a price for panels for my home...$7000...not sure what that entails either....I WANT to be off the grid- but sure is easy to write a check for $120.00 a month to the electric company. Thanks.

For total OFF GRID of course you need battery energy storage plus a big enough inverter for your needs. And that gets EXPENSIVE. Grid tie (panels and charge controller) if available and you want it is much cheaper to install

John T

Batteries are really expensive , but sometimes you can find a bargain at scrapyards . Look for large banks that have been removed from hospitals and other public buildings . These are often replaced on a cyclic maintenance programme and are usually still very serviceable.
I asked the local scrap man to keep one aside for me , it cost Aus $140. for the bank of six of them , the same batteries new are almost $1700 [u:057f9f2245]each[/u:057f9f2245] here . They are not much below new capacity and were used as an emergency lighting system at a local geriatric centre .

I'll add just one more word: Don't buy the cheap stuff, get American virgin copper even if you have to pay double or more. The Chinese take our scrap copper, do no more cleaning than necessary and sell it back to us as good wire. Some of it could be used as resistance wire, not what you want for large amps.

What is "Grid tie" ?

(quoted from post at 06:10:44 09/09/17) What is "Grid tie" ?

Click to expand...

The interface between your solar setup and the power company, allows you to sink your extra output to their system and gives you power when the sun don't shine.

One of my neighbors has solar heat collectors on his roof with an insulated tank of water in his basement. Seems more efficient and a lot cheaper than converting to electricity, holding that in a battery, then using it to heat water. Your mileage my vary.

No need for a battery to heat water.
Take an ordinary electric water heater and replace the 220V elements for 48V rated at 1kw. Install a 1.5kw of 48V solar panels out side. Insulated water tank stores the hot water .
Can get really wild and wire up enough panel$$$ to operate the 240V heating elements .

Its connection of your solar system to the utility grid so you sell power back to the utility when youre producing. If you don't grid tie then you need battery storage and an inverter to power up your AC loads.

John T

While on the subject of panels, how do they do in a hail storm?????

How long have the ones you are replacing been in service? Why do they need replacing?