Series or Parallel 9 panels on a pole mount

[Sean Montana]

Hi all, I have 9, 310 watt panels to be put on a pole mount about 200ft away from the off grid house. Should they be connected in parallel or series? Also, would 10awg be the size wire I should use for the 200ft run?
Thank you!

[J.P.M.]

Assuming you're running the house on 120 V AC, wire and string size depends on how and where you convert from DC to AC and the particulars of the inverter(s) - string or micros - you're using as well as where the inverter(s) is/are located. See local codes or tables for min. safe/required wire sizes as f(wire length, max. line voltage) and don't forget to take min/max ambient air temp. into account when estimating max. panel voltage.

[Sean Montana]

Thank you JPM. Yes 120 v ac & will be converted from dc to ac at the cabin. Its string and not micro. I will find out the rest. Thank you again!

[SunEagle]

Hi all, I have 9, 310 watt panels to be put on a pole mount about 200ft away from the off grid house. Should they be connected in parallel or series? Also, would 10awg be the size wire I should use for the 200ft run?
Thank you!

If you are worried about voltage drop (AC or DC) then wiring the panels in series should get you the highest DC voltage. You didn't mention if you are using an inverter or battery charger to convert to AC and where that is being done. So to really answer your question will require a little more information on your system.

[bcroe]

At that distance you need a series setup, to get reasonable
efficiency with reasonable size wire. Run the figures on the
resistance of 400 ft loop of 10ga and see why. Bruce Roe

[littleharbor2]

Hopefully your inverter will accept high dc voltage. If not, the only option I see with 9 panels would be 3s3p. This would likely yield too low of voltage and a higher current than you want to push that distance.

[Sean Montana]

Thank you everyone! There's a Midnite Solar Inverter at the cabin appx. 200ft away & a Midnite solar tri star charge controller. I don't have the inverter model info just yet.

[littleharbor2]

Do you mean Morningstar Tri Star charge controller? Do you happen to have a model number or system voltage of the Midnite Solar inverter?

[Ampster]

The charge controller will determine the maximum voltage which is a hard limit. Be sure and use the lowest temperature in your area to correct the maximum voltage from your panels. It may be a trade off between a new controller to be able to run nine in series or the cost of heavier wire to run one third lower voltage on a 3P3S configuration, Voltage loss is less of a concern with high voltage DC, than utility AC voltages which often have a tighter spec and the AC devices may have less tolerance for voltage sag than a 400 volt DC charge controller. What is the VOC of your panels and what is the lowest temperature in your area?

[Sean Montana]

The Solar Controller is a Tri Star TS-45 by Morning Star.
There is also a black MidNite Classic
Inverter is a Midnite Solar Inc. Conext -SCP by Schnieder Electric
The is also a Conext SW by Schnieder Electric.

[Sean Montana]

This is connected in series to 8 6 volt deep cell batteries

[Sean Montana]

Electrician that put this in originally moved away & the new electrician isnt up to speed yet on solar. I'm learning & trying to make sure its done right. Thank you everyone I appreciate your wisdom & time!
Q: Biggest question is can we use 10awg thhn in conduit underground to run the 200ft to the system?
Q: If the panels are grounded at the pole, is there a need run a ground with the wire the 200ft (Im learning if its a dumb question lol)

[Ampster]

.........
Q: Biggest question is can we use 10awg thhn in conduit underground to run the 200ft to the system?
.......

What is the VOC of your panels and what is the maximum voltage of your charge controller? That will help answer the quesiton because voltage drop varies by voltage. The original question about series or parallel depends on those variables.
If it is 200 feet in DC you should figure 400 ft to calculate voltage drop.

[jflorey2]

The Solar Controller is a Tri Star TS-45 by Morning Star.

That's a 125V limit.

There is also a black MidNite Classic

There are several classics. There is a 150, 200 and 250 volt version. The 150 is the most common.

So what you will be doing is adding up panel voltages at the coldest temp you might see and seeing how long a string you can connect without overvolting anything. For examle if you have Silfab Solar SLA-M310 panels, their OCV is 40.3 volts. You will likely need to go to 45 volts or so for cold in your area - but you must calculate this for yourself. With those you could do a 3s3p on the Classic if it's a 150. You could do a 2s4p on the Tristar. But of course with the lower series numbers you will need heavier gauge wire.

Once you know all that you can calculate the wire you need based on NEC tables and based on the loss you want to achieve. You cannot go thinner than NEC tables but you can go thicker to reduce loss.

[littleharbor2]

[QUOTE=jflorey2;n439663]
That's a 125V limit.

It's that high because of it being a 12/24/48 volt controller. It's not an MPPT controller and you have nothing to gain by putting high voltage into it. Being a PWM type controller you want to wire your panels in a 12, 24 or 48 volt nominal voltage configuration, matching the system voltage..