Can I wire together panels in 5s2p together with a 5s?

[AV!611]

I am looking to wire up the above panel configuration. The voltage of the 5s2p string would be the same as the 5s string, correct? If this does work, how would the wiring look if the panels were laid out physically as in the attached picture? Also, I have been trying to find an online tool that will let me enter the number of panels in parallel and series and show me how the wires would be laid out and connected to the combiner box and then to the charge controller. Thank you.

edited for content: Oh, yes. The front of the house faces east. There is a big oak tree in front of the house and one behind the house.

 

[Bud Martin]

You are asking about 5s3p, correct?
If all 15 panels have the same spec, and all 3 strings (each string has 5 panels in series) connected in parallel, 5s3p, then yes each string will have the same total Voc.

 

[BentleyJ]

All 3 strings will have the same Voc. However, Since 2 strings are on the West facing roof while 1 string is on South facing roof the actual voltage and current will not be the same throughout the day. To maximize output it would be best to use 2 charge controllers, one for the 5s2p array on the West and one for the 5s array on the South. There are 2 advantages with above. 1) You get more overall production because the MPPT SCC will maximize for each orientation based on the sun angle and the string will not degrade performance. 2) You shouldn't need a combiner box, use a "Y" connector for the 2 West roof strings and the South string wires directly to the other SCC, this simplifies your installation. What you save on the combiner box can be put towards the second charge controller.

 

[Hedges]

SMA did a test (report no longer on-line) and found separate MPPT per orientation yielded 2% more power.
The penalty of paralleling two strings of different orientations is minimal.
I believe the watts per dollar is improved, due to more hours of good production from the charge controller.

Where performance is poor is when one string has large percentage of panels shaded. Then, the still illuminated panels in that string deliver nothing, whereas on a separate MPPT they could (if voltage still within MPPT range.)

Fuses an Bentley said, when 3 or more strings in parallel.
No need for anti-backfeed diodes, however. Zero current will leak back (because what little light they do see still produces sufficient Voc.)

 

[AV!611]

All 3 strings will have the same Voc. However, Since 2 strings are on the West facing roof while 1 string is on South facing roof the actual voltage and current will not be the same throughout the day. To maximize output it would be best to use 2 charge controllers, one for the 5s2p array on the West and one for the 5s array on the South. There are 2 advantages with above. 1) You get more overall production because the MPPT SCC will maximize for each orientation based on the sun angle and the string will not degrade performance. 2) You shouldn't need a combiner box, use a "Y" connector for the 2 West roof strings and the South string wires directly to the other SCC, this simplifies your installation. What you save on the combiner box can be put towards the second charge controller.

I am actually planning on buying this:

EG4 6.5kW Off-Grid Inverter | 6500EX-48​

I understand it has dual 60 amp mppt's in it.

 

[wattmatters]

I am actually planning on buying this:

EG4 6.5kW Off-Grid Inverter | 6500EX-48​

I understand it has dual 60 amp mppt's in it.

No issues, just connect 5s2p into one MPPT and the south string 5s into the other MPPT. No need for a combiner box for the west array.
Just use Y-connectors to parallel the two strings.

 

[AV!611]

View attachment 100845

No issues, just connect 5s2p into one MPPT and the south string 5s into the other MPPT. No need for a combiner box for the west array.
Just use Y-connectors to parallel the two strings.

How hard a limit is that 500 Voc rating? I'm looking at a panel setup that tops out at 508.

 

[wattmatters]

How hard a limit is that 500 Voc rating?

Very hard. Above that definitely risks damage to the charge controller.

Keep in mind panel Voc increase as temperature drops so you need some safety margin.

 

[Hedges]

How hard a limit is that 500 Voc rating? I'm looking at a panel setup that tops out at 508.

Based on PV panel data sheet (for 25 degrees C)?
Assume 16% increase in voltage (508V x 1.16 = 589V) until you've calculated a more precise figure.

 

[AV!611]

Okay, so I found some panels that I think would work perfectly with my roof size and layout as well as maximizing the EG4 6500EX-48 charge controller/inverter. Santan Solar has some new in box 390 watt Canadian Solar HiKu panels with a VOC of 44.1 and Isc of 11.38. https://store.santansolar.com/wp-content/uploads/2022/03/document.pdf I am planning on putting 5 of them on the south roof wired in series. So, 5 * 44.1v or 220.5 total volts and 11.38 amps. On the west roof I would wire 10 panels as 5S2P keeping the voltage for those 10 panels at 220.5, but increasing the amps to 22.76. So, Y connecter to connect the 5S2P together and send that power to PV input #1 on the EG4, and a second wire to send the power from the south array to PV input #2 on the EG4.

I believe the two 60 amp mppt's in the EG4 can handle 4,000 watts input each. Please correct me if I'm wrong. For the time being, the west array would send 3,900 watts to mppt #1 and the south array would send 1950 watts to mppt #2 for a total of 5,850 watts. If I later added another 5S string to the south array, the voltage on the south array would remain at 220.5, and the amperage would increase to 22.76 for a grand total of 7,800 watts at 441 volts (the EG4 states max Voc is 500) and 22.76 amps each to mppt #1 and mppt #2. Thoughts?

edited for clarity: Please ignore the Voc and Isc in my diagram. They are for a different panel that won't work for me.

 

[wattmatters]

So, Y connecter to connect the 5S2P together and send that power to PV input #1 on the EG4, and a second wire to send the power from the south array to PV input #2 on the EG4.

Yep.

I believe the two 60 amp mppt's in the EG4 can handle 4,000 watts input each. Please correct me if I'm wrong. For the time being, the west array would send 3,900 watts to mppt #1 and the south array would send 1950 watts to mppt #2 for a total of 5,850 watts.

The MPPTs are not rated for 60A input. That's the battery charging current limit. When I looked up the model you posted earlier the MPPT solar PV DC current limit is 18A.

The MPPT inputs will clip current to their rated 18 A, so the parallel arrays are unlikely to generate right up to their max rated capacity under perfect solar conditions. The MPPTs however will have a fair bit of voltage heardoom though to extract what it can from the clipped current.

This clipping is not going to be a lot or often, so it's rarely going to be an issue. Perfect Summer day early afternoon perhaps. Nothing wrong with such a design.

If I later added another 5S string to the south array, the voltage on the south array would remain at 220.5, and the amperage would increase to 22.76 for a grand total of 7,800 watts at 441 volts (the EG4 states max Voc is 500) and 22.76 amps each to mppt #1 and mppt #2. Thoughts?

I'd be surprised if the MPPT voltage limit was for both MPPTs combined. It should be a 500V limit for each MPPT.

Check the specs or confirm with EG4.

 

[AV!611]

I e-mailed Signature Solar tech support. He confirmed that the Voc limit is 450v per MPPT. So, 450v each.