Moved and new house has an old system

[Damil 1776]

Howdy, I am a novice solar junkie, I moved in to a house that has 4×100 watt panels, the panels are on a ground mount over 45 ft away from the solar charger, they had the system under wired with 10 awg and the charge controler had burnt out, I got a new pwm controller 40 amp and ran 8 awg. Realizing later that this is also under rated for the length, I have since disconnected the system until I can set it up correct, the panels say they produce 5.75 or 23 amps in parallel. Before I disconnected the system it would only charge at 15.4 amps. If I move the system closer to the house I lose 4 hours of sunlight, I can not afford to get larger wires, The question, if I did my calculations right I can run 15 ft of 8awg to get full charging amps, there is no good spot to place it in the sun, if I go 20ft I get a 5% loss but have decent sun, can I go 15ft of 8awg, then splice 5 ft of 12awg and get less loss?

 

[DThames]

Get an MPPT charger and connect all 4 in series. You will have less than 7 amps on a #8 wire and be much better off.

 

[Damil 1776]

Get an MPPT charger and connect all 4 in series. You will have less than 7 amps on a #8 wire and be much better off.

Wish I could but 24v inverter is our of budget

 

[DThames]

Wish I could but 24v inverter is our of budget

 

[Rednecktek]

Wish I could but 24v inverter is our of budget

Do you mean charge controller or inverter? If you're running a 12v system you'll want a 40a SCC, if it's 24v then a 20a will be fine. The higher the voltage you can go the less noticeable the voltage drop is. 8% of 20v hurts a lot more than 8% of 80v, but the 8% you should have now isn't too horrible as it is.

If you mean inverter then that doesn't care about the MPPT controller.

Just using a PWM controller is nerfing your system by about 25% as it is.

can I go 15ft of 8awg, then splice 5 ft of 12awg and get less loss?

In theory, yes. You'll want to keep as much of the larger cable as you can but there's no reason it won't work.

 

[DThames]

The voltage drop and power loss are directly tied to the amps, not the power. So for 1000w, if you have the choice between 50 amps at 20 volts or 12.5 amps at 80 volts, the 80 volt circuit will have 25% the voltage drop, 6% the power loss as the 50 amps with the same size wire. You would have been much better off to leave the 10ga wire in place and spend your wire money on an MPPT charger so you could put your panels in series and drop the amps way down.

 

[Supervstech]

Wish I could but 24v inverter is our of budget

What inverter do you have now?

What batteries?
#8 will work, and supply a good amount of the voltage, but plan to upgrade to mppt, and you will be much happier.

 

[Rednecktek]

Pro Tip: If it's got USB ports on the front, it's NOT a real MPPT controller, it's just a dirty dirty LIAR!

Also, how much does 20+ ft of #8 copper cost VS a 40a MPPT controller? Even the cheapest HQST or RichSolar or even a MakeBlueSky will turn PV DC volts into Battery DC volts!

 

[Damil 1776]

What inverter do you have now?

What batteries?
#8 will work, and supply a good amount of the voltage, but plan to upgrade to mppt, and you will be much happier.

Ancient 8 year old lead acid deep cycle batteries, that are reaching the end of their life span, I have two inverters I 1500 watt roadwork inverter and a 2000 watt power drive, both are reminants of my trucking days, the 2000 watt uses to much power at idle so I use the 1500 watt most. To be honest I live very rural and due to economic down turn in the area am unemployed, so my electric life has been reduced to this 400 watt system, Not a complaint or whine or beg, just the facts of life, I only use the system to run my fridge for 6hrs a day , she is ancient and not very efficient either 2.18 amps once cool 4 amps to cool it, and a fan thru out the night, so by moving it I would be ecstatic to gain 2 to 3 amps and make the panels moveable to gain more sun time. A new charge controller will be my first purchase, when life turns around again as it always does out here in the sticks, thanks for the reply

 

[RVLiFe]

Isn’t 15’ actually 30’ round trip? Or do you only rate the size of the wire based off one direction?

 

[Damil 1776]

Isn’t 15’ actually 30’ round trip? Or do you only rate the size of the wire based off

I have only figured it out as one direction, as dc current only travels in one direction, as opposed to AC current that travels both ways

 

[RVLiFe]

I have only figured it out as one direction, as dc current only travels in one direction, as opposed to AC current that travels both ways

This is what I have thought as well but I was told by a solar installer to figure it as round trip. Probably told me that to sell me more equipment and/or higher gauge wire. Now that I know that, looks like I could wire my panels twice as far away as they currently are without issue.

 

[Damil 1776]

UPDATE
Moved the system today, used 20 ft of #8 went from 14.9 amps to 19.5 amps, I am dancing a jig, Thank you all for your input.

 

[Supervstech]

I have only figured it out as one direction, as dc current only travels in one direction, as opposed to AC current that travels both ways

All voltage travels out, then back to source..
Ac reverses direction 60 times a second, but the energy goes out and back to source.
Some wire calculation charts figure the round trip length,some only need the single length. It doesn't depend on the voltage type, it depends on the calculation method.

 

[brahmasick1]

Nice thread, thanks! I found it because I googled a similar issue. I have also moved to a new house with a solar system I didn’t understand. It took me some time, but I did figure out how that thing works and how I can adjust to my needs. I want to set my financial record straight, which is a part of it. I have already talked to Equity Release Bristol, and they told me I have to be more careful with the solar system and estimate all the prices correctly. Otherwise, it might cause some issues with the total finances. Managing finances might be difficult, but I must learn that.