Need to Reduce solar voltage!!

[vashkoproimage]

This is unhelpful, but when I went back and saw 535W panels were being used, I thought, "This is really a Great power / Great responsibility situation; if you want to use things that big you should also do big investment in planning & researching up front." Vs the safety of numbers of using standard normal residential sizes (and by extension voltage/currents) like 400W +/- 50W.

#10 was also the wrong choice if starting with the cell size with 13A I_mpp and a non-trivial probability of going to parallel strings.

I have close to 20kw of these panels for future setup when house is built. I’m just trying to use this 6kw hybrid inverter with 145v max because it’s been collecting dust for about a year now. The 6kw output works for me for a temporary setup. Just trying to get the solar input to the max I can safely.

 

[Jet]

I can’t do 3s2p. The distance is too far and the voltage will be too low for my 10 gauge wire. I need the voltage to be on the higher side to keep amps down to get away from running long distance. That’s why I went with 2s3p. If I was to running 3s2p then I will have to run 8-6 gauge wire to be under the 3 percent voltage drop.

The difference in voltage drop between 94V and 142V is insignificant. The main determining factor in voltage drop is amperage. If you add another PV circuit (2s3p/3 circuits) you will have the same average per circuit as 3s2p. It might be cheaper to buy a higher voltage mppt then the wire depending on the run length assuming you sell the other one. Unless you have an all in one inverter/mppt (unless it's a modular one ex: Outback Solar).

 

[zanydroid]

I have close to 20kw of these panels for future setup when house is built. I’m just trying to use this 6kw hybrid inverter with 145v max because it’s been collecting dust for about a year now. The 6kw output works for me for a temporary setup. Just trying to get the solar input to the max I can safely.

To summarize my contributions to the thread

2s1p to comply with NEC Isc limits on #10

2s2p if you don't care about that and just care about not smoking the MPPT

 

[Zwy]

Hello everyone. Need to reduce solar voltage on my temporary system. Running 2 sets of (3) 535 watt panels. Controller voltage is 145 max. I hitting that mark. On warmer days I get around 139-140v. This week was colder so I hit the 145-150v mark. I need to drop voltage by 5-10v before going into controller. Any ideas? For now I unplugged 1 panel off each array. Running 3 sets of 2 panels is out of question because of the distance between controller and arrays. View attachment 179235View attachment 179236

Purchase the EG4 48V charge controller. I run a pair and they work very well after updating the firmware. I did review this unit on Youtube both before and after the firmware update. Have worked flawless since the firmware update. It will take 5.5Kw at up to 450V operating voltage.

 

[740GLE]

The difference in voltage drop between 94V and 142V is insignificant. The main determining factor in voltage drop is amperage. If you add another PV circuit (2s3p/3 circuits) you will have the same average per circuit as 3s2p. It might be cheaper to buy a higher voltage mppt then the wire depending on the run length assuming you sell the other one. Unless you have an all in one inverter/mppt (unless it's a modular one ex: Outback Solar).

He never said how had the panels wired up from say a combined box or mc4 splice to the SCC.

I think assumption was 10awg for his home run from splice/combiner box to the SCC.

 

[vashkoproimage]

To summarize my contributions to the thread

2s1p to comply with NEC Isc limits on #10

2s2p if you don't care about that and just care about not smoking the MPPT

I’m not running the entire system on only (1) set of 10 gauge wire bro. I’m running 2 sets of wires (3 panels) 160ft and second set of wire 100ft distance. And that’s total lengths including positive and negative runs. More than sufficient for 2s3p.

 

[Hedges]

2s2p or 3s2p.
Orient strings differently so the don't all make max current at the same time.

10 awg 90 degree C wire actually has ampacity 40A; it is only the code police who say 30A.

Code says Isc x 1.56, but that's related to nuisance tripping of thermal breakers.
Magnetic-hydraulic breakers don't need the second 1.25x for nuisance trip. That leaves just 1.25x for cloud edge effects (not 1.56x).
Anything beyond that is code writers, not physics or engineering.

Or buy a higher voltage charge controller, as suggested, and let that charge the battery feeding your inverter.

 

[740GLE]

So

I’m not running the entire system on only (1) set of 10 gauge wire bro. I’m running 2 sets of wires (3 panels) 160ft and second set of wire 100ft distance. And that’s total lengths including positive and negative runs. More than sufficient

How do the two strings of 10awg connect to the SCC?

 

[Jet]

2s2p or 3s2p.
Orient strings differently so the don't all make max current at the same time.

10 awg 90 degree C wire actually has ampacity 40A; it is only the code police who say 30A.

Code says Isc x 1.56, but that's related to nuisance tripping of thermal breakers.
Magnetic-hydraulic breakers don't need the second 1.25x for nuisance trip. That leaves just 1.25x for cloud edge effects (not 1.56x).
Anything beyond that is code writers, not physics or engineering.

Or buy a higher voltage charge controller, as suggested, and let that charge the battery feeding your inverter.

2s2p is 4 panels and 3s2p is 6.

 

[Jet]

So



How do the two strings of 10awg connect to the SCC?

2 sets of wire is two strings not three.

 

[vashkoproimage]

So



How do the two strings of 10awg connect to the SCC?

2 Y Branch Connectors before controller. Then single wires through pv breaker then to controller. From Y connectors to controller it’s about 6 feet of total wire. That’s 26 amps running at 126v at normal operating conditions through 6 feet of wire.

 

[740GLE]

So string #1 had 3 panels, string #2 had 3 panels.

Is there any way you could convert string #2 to a 2s2p with a y junction at the panels, same 10awg back to your SCC, then where string 1 and 2 combine up that 6 foot run to #8 or something larger?

2s2p is perfectly fine for 10awg.

 

[kendive]

I can’t do 3s2p. The distance is too far and the voltage will be too low for my 10 gauge wire. I need the voltage to be on the higher side to keep amps down to get away from running long distance. That’s why I went with 2s3p. If I was to running 3s2p then I will have to run 8-6 gauge wire to be under the 3 percent voltage drop.

You need bigger wire... Go 6ga or go home.

 

[vashkoproimage]

To summarize my contributions to the thread

2s1p to comply with NEC Isc limits on #10

2s2p if you don't care about that and just care about not smoking the MPPT

I think it’s a misconception that a ssc will start smoking if supplied over-voltage. My controller personally will not supply any charge with overvoltage. It just cuts pv input off when over 145v. Can’t say this about all scc are this way.

 

[vashkoproimage]

You need bigger wire... Go 6ga or go home.

Sarcasm? Lol Explain why I need thicker wire with running 2s3p setup I have?

 

[Jet]

So string #1 had 3 panels, string #2 had 3 panels.

Is there any way you could convert string #2 to a 2s2p with a y junction at the panels, same 10awg back to your SCC, then where string 1 and 2 combine up that 6 foot run to #8 or something larger?

2s2p is perfectly fine for 10awg.

A lot of building codes require the wire to have circuit protection 1.56 times ISC. 10 AWG solar has a maximum of 30 amp SP if ran outside. This makes the maximum panel IEC 9.61A when paralleled (19.22 total). Panels above 350 watts (sometimes less sometimes more depending on number of cells and the resulting voltage) often exceed 9.61 amps. This restriction doesn't apply to 8 awg. You 55 amps at 75C or 17.62 ISC per panel. With a 50 amp breaker you can have 16.02 ISC panels.

 

[zanydroid]

I think it’s a misconception that a ssc will start smoking if supplied over-voltage. My controller personally will not supply any charge with overvoltage. It just cuts pv input off when over 145v. Can’t say this about all scc are this way.

I’m only aware of MidNite HyperVoc feature that guarantees a cushion above its max VOC cutoff.

For any hypothetical SCC, how would the controller protect itself if say the input FETs are rated to 150V? Or FET based BMS. It’s somewhat counterintuitive to analyze the voltage across a FET in these kinds of conditions.

Any SSR automatic disconnect would potentially need to be rated to the higher voltage as well as able to carry the current density… in which case maybe those FETs inside should have been used as the power FETs in the first place

 

[vashkoproimage]

This is the setup I had issue with over voltage. 3s2p

 

[zanydroid]

A lot of building codes require the wire to have circuit protection 1.56 times ISC. 10 AWG solar has a maximum of 30 amp SP if ran outside. This makes the maximum panel IEC 9.61A when paralleled (19.22 total). Panels above 350 watts (sometimes less sometimes more depending on number of cells and the resulting voltage) often exceed 9.61 amps. This restriction doesn't apply to 8 awg. You 55 amps at 75C or 17.62 ISC per panel. With a 50 amp breaker you can have 16.02 ISC panels.

Where is the 30A limit listed in code? I have been confused about 30 vs 35 because there is no need for OCPD, and often #10 is allowed to carry 35A circuits on 75C terminations in cases where OCPD over 30A is allowed

I would say the majority of new 400W panels sold today are in 12A+ range due to the prevalence of 54 cell in the inventory. Which is why I’ve suggested #8 for hauling back from an array if there’s a decent chance it might be expanded…

 

[Bluedog225]

Why not run additional wire for the higher amps?

 

[timselectric]

I think it’s a misconception that a ssc will start smoking if supplied over-voltage. My controller personally will not supply any charge with overvoltage. It just cuts pv input off when over 145v. Can’t say this about all scc are this way.

It hasn't yet. But, it's just a matter of time before your luck runs out.

 

[vashkoproimage]

It hasn't yet. But, it's just a matter of time before your luck runs out.

Lol Did you even read the post? I already disconnected 1 panel of each array. Total of 4 panels running now in safe zone. Trying to find a solution to lower voltage down 5-10 volts for previous setup.

 

[740GLE]

A lot of building codes require the wire to have circuit protection 1.56 times ISC. 10 AWG solar has a maximum of 30 amp SP if ran outside. This makes the maximum panel IEC 9.61A when paralleled (19.22 total). Panels above 350 watts (sometimes less sometimes more depending on number of cells and the resulting voltage) often exceed 9.61 amps. This restriction doesn't apply to 8 awg. You 55 amps at 75C or 17.62 ISC per panel. With a 50 amp breaker you can have 16.02 ISC panels.

How much current would be pushing in a 2s2p set to his y combiners?

2x isc, that’s still well under 10awg of the 100‘ or 165’ run back to his SCC.

 

[740GLE]

This is the setup I had issue with over voltage. 3s2p

And those wye connectors are near the SCC right?

 

[timselectric]

Lol Did you even read the post? I already disconnected 1 panel of each array.

That was an earlier post. I was replying to the last post.

Total of 4 panels running now in safe zone.

But you said that it wasn't going to be enough production.

Trying to find a solution to lower voltage down 5-10 volts for previous setup.

You will be much better off spending money on the right equipment. Rather than a bandaid, for the current mistake.