Need to Reduce solar voltage!!

[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.

 

[Hedges]

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.

Open junction box and move PV wire connection over one diode-bypassed section. That is, leave off 1/3 of the cells in one panel.

But consider 2s3p, with multiple orientations. That may fit within specs and physics, if not code, and make use of all cells.

 

[Jet]

Is that before or after you derate the wire? Anyway, it's not particularly unsafe and with that long of run wire is expensive. That's why you're getting the voltage dropped though. 10 AWG is your standard size/smallest typically used on houses solar wire. 535 watt panels are some big panels.

 

[740GLE]

Open junction box and move PV wire connection over one diode-bypassed section. That is, leave off 1/3 of the cells in one panel.

But consider 2s3p, with multiple orientations. That may fit within specs and physics, if not code, and make use of all cells.

He has two arrays currently 3s and 3s, each with a 10awg decently long “home run” to within 6 feet of the SCC, not sure if he can rig up one array to hold 4
panels.

 

[vashkoproimage]

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

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

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

So does it make sense to buy a 20kw solar inverter for my future setup and use it for these 6 panels? That’s how much panels I have when house is built. Why run a new 20kw inverter when all I need 6 panels while building house. Does not make sense until larger setup is needed. This is just a temporary setup and will be torn down once new one is up. My current 6kw works just fine for what I’m using it. All I’m trying to do it connect as much as can for temporary setup. If I have extra equipment laying around why not just use what I have if temporary? Make sense to you?

 

[vashkoproimage]

He has two arrays currently 3s and 3s, each with a 10awg decently long “home run” to within 6 feet of the SCC, not sure if he can rig up one array to hold 4
panels.

 

[vashkoproimage]

And those wye connectors are near the SCC right?

Yes. 6 feet from controller.

 

[timselectric]

So does it make sense to buy a 20kw solar inverter for my future setup and use it for these 6 panels? That’s how much panels I have when house is built. Why run a new 20kw inverter when all I need 6 panels while building house. Does not make sense until larger setup is needed. This is just a temporary setup and will be torn down once new one is up. My current 6kw works just fine for what I’m using it. All I’m trying to do it connect as much as can for temporary setup. If I have extra equipment laying around why not just use what I have if temporary? Make sense to you?

If you just need a temporary solution.
Then hedges gave it to you.

Open junction box and move PV wire connection over one diode-bypassed section. That is, leave off 1/3 of the cells in one panel.

Do this to one panel in each 3s2p string.

 

[vashkoproimage]

Open junction box and move PV wire connection over one diode-bypassed section. That is, leave off 1/3 of the cells in one panel.

But consider 2s3p, with multiple orientations. That may fit within specs and physics, if not code, and make use of all cells.

Leaving 1/3 cell might actually work.? never took off the junction box and messed with it. Any tips on this?

 

[Hedges]

You can use it until it dies.
Our recommendation is to ensure voltage, even in cold, does not exceed SCC or inverter spec.

Leaving 1/3 cell might actually work.? never took off the junction box and messed with it. Any tips on this?

Designs vary. Some have 3 small boxes. Others one with a screwed on lid, others glued.

Disconnect from other panels in the string before messing with it! (shut off to stop current before disconnecting.)
If you can get in there, either move the PV wire or just short out any one bypass diode.

 

[pollenface]

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.

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.

So are you doing 2s3p now? Problem solved?