Long Distance runs - A common issue?

[sunsurfer]

I was going to reply to another thread about long distance runs being a common challenge but I thought I would just start a new thread. Please share your long distance setup and what works.

I know there are allot of unique situations. Going forward, allot of people are moving to land and off-grid. Allot of times, there is only 1 or 2 good spots for panels and the "cabin" is better elsewhere or multiple buildings and residents.

I am in one of these situations. My sunny spot is not where the house is going. Current cabin I live in is also a ways form the solar panels and it was better to put all the gear in a shed between the panels and cabin about 75' from panels and 160' from Cabin. I'm running 3 leads of 120v AC to the cabin. My setup is multi MPPTs with 80V strings. I'm 12V. Next system will be 48v with higher voltage strings. Still multiple MPPTs and inverters though. I don't like the AIO approach.

I will have a second cabin next year with minimal power needs that will be 600' from the panel field. Current thougt was to move 200vish DC(250v MPPT) from panels direct to the cabin over 600'. Probably a single 10gauge/5amp run.

This subject could almost have its own sub forum, it seems to be a tricky ordeal many go through moving power where it needs to go.

 

[BentleyJ]

At a distance of 600', voltage drop becomes significant. I would have to believe that a high voltage solar charge controller or choosing an all in one inverter with a 500VDC MPPT input would be the best choice. The cost savings in being able to use smaller wiring should offset any higher costs for the high voltage DC equipment.
The other consideration is the process of installing conduit and pulling wire that far. Smaller wire weighs less and requires a smaller diameter conduit which also costs less.
You would have to do the math based on your specific conditions and needs but its hard to see where higher voltage would not be a big advantage.

 

[SamDeleted]

Have you thought about inverting it at the panels and moving the power at 240VAC ?

 

[timselectric]

Have you thought about inverting it at the panels and moving the power at 240VAC ?

That would be less efficient.
Higher voltage travels more efficient.
DC array voltage can be designed much higher.

 

[Northernchateau]

Two things:
1st. I always use this to check for wire amp rating plus voltage drop over a distance. If your on the line go a wire size bigger.

Wire Sizing Chart for 12V/24V/48V DC Systems - DIY Solar Resources

Information on wire sizing and a universal AWG/mm2 wire sizing chart to help in designing a 12V, 24V, or 48V DC renewable energy system.

www.altestore.com

2nd. I don't know about where you live but 2 times critters ate thru my burried UFB cable. Good thing I had it on a GFI breaker.

 

[Substrate]

Note that if you consult some charts, be *SURE* to confirm whether the chart is either a "one-way" or "two-way" (out and back) chart.

 

[sunsurfer]

Two things:
1st. I always use this to check for wire amp rating plus voltage drop over a distance. If your on the line go a wire size bigger.

Wire Sizing Chart for 12V/24V/48V DC Systems - DIY Solar Resources

Information on wire sizing and a universal AWG/mm2 wire sizing chart to help in designing a 12V, 24V, or 48V DC renewable energy system.

www.altestore.com

2nd. I don't know about where you live but 2 times critters ate thru my burried UFB cable. Good thing I had it on a GFI breaker.

Good to know about the buried cable. I have every kind of critter imaginable out here. Would PVC conduit be the best choice?

I've done some pretty long cable pulls. We used allot of the pull gel.

 

[Northernchateau]

Good to know about the buried cable. I have every kind of critter imaginable out here. Would PVC conduit be the best choice?

I've done some pretty long cable pulls. We used allot of the pull gel.

I think PVC would avoid the issue. My thing was that run is 500 feet long so the cost made me try just UFB cable. Below is what I dug up and found.

 

[Bluedog225]

That looks electrical. Are you sure critters?

 

[timselectric]

Maybe a nick in the cable got wet.

 

[Northernchateau]

That looks electrical. Are you sure critters?

The ground right where they was had been disturbed big time. Something had been digging.
What ever it was chewed the coating off and tt turned into an electrical problem.
My buddy that is an electrian says he sees it all the time with buried cable in my area.
The best part was that was on a GFI breaker. It tripped a few times but always reset.
I found it but disconnecting both ends and throwing a Ohm meter on it.

 

[OzSolar]

I believe that NEC code requires you to size the wire between the array and the inverter or charge controller at Isc x 1.56.

Since your array will spend most of its life at less than NOTC which in many cases will be ~30-50% below Isc you won't have much of a voltage drop issue until runs get pretty long. I might try to put a chart together sometime.

 

[Mattb4]

...

I will have a second cabin next year with minimal power needs that will be 600' from the panel field. Current thougt was to move 200vish DC(250v MPPT) from panels direct to the cabin over 600'. Probably a single 10gauge/5amp run.

...

I would consider that to be impractical especially if, as you say, the cabin has minimal needs. You would be better off to have a setup at the panels to charge up a portable power unit that you can than power the cabin with maybe two of them that can alternate being charged.

 

[Pete@SolarBatteryBarn]

10 guage wire is 1 ohm per 1000 feet so a 600 foot run wit be 1.2 ohms (round trip).
You expect to run 5 amps so your voltage drop will be 6 volts or about 30 watts.
Keep in mind this loss is less significant under lower current conditions (less sun) so it has less impact when you really need more power.
For me it is far more economical to just add more PV power than thicker wire.

 

[sunsurfer]

I would consider that to be impractical especially if, as you say, the cabin has minimal needs. You would be better off to have a setup at the panels to charge up a portable power unit that you can than power the cabin with maybe two of them that can alternate being charged

I probably should not of used the term minimal...lol. It will have a 5,000 BTU window unit running in the summer which will need 450watts continues plus a small fridge.

Your idea would work good otherwise.