Series or Parallel 9 panels on a pole mount

[sdold]

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

In the US, underground conduit is considered a wet location and you'd need something with a "W" (wet) like THHW. I think most THHN is dual-listed THHN and THHW anyway. Welcome to the forum!

[Sean Montana]

Just want to say you're all good people for helping others out! And not making them feel dumb because their learning. THANK YOU : )

[jflorey2]

If I recall, MPPT controllers are more efficient than PWM type controllers?

In most cases, yes.

[littleharbor2]

MPPT, watts in = watts out, minus a few percent.
PWM, x amps in @ any voltage = x amps out @ battery voltage. The bigger the voltage differential the more loss of efficiency.

[Ampster]

[QUOTE=littleharbor2;n439670]

That's a 125V limit.
......,. Being a PWM type controller you want to wire your panels in a 12, 24 or 48 volt nominal voltage configuration.

If it were me, I would do some scenarios to see where the tradeoff would be to buy a MPPT controller that could run a higher voltage so I could use smaller wire on those long runs. The saving in wire might pay for a new controller. If I recall, MPPT controllers are more efficient than PWM type controllers?

[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..

[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.

[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.

[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)

[Sean Montana]

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

[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.

[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?

[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?

[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]

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.