Pv combiner box keeps throwing 80amp breaker

[Jazzmonger]

One of my combiner boxes keeps throwing the breaker. It's happened multiple times now.



Brand new install - I have 3S4P config on Canadian Solar 420 watt panels. I see the current touching 80amps from time to time. The breaker says
In-80A, I'm assuming that's the trip value. Solar Assistant shows 80A peaks, but not at the time it tripped. Im sure there's a delay in the reporting of values. It's too bad there not a table of max/min values for each stat.


Options:
I could move one of the parallel strings to my second combiner box to reduce the input current. The other box has the same number of panels but only shows 2/3 the current as the overloaded box for some reason - that's a topic for another thread.

Any other ideas?

Jeff

 

[sunshine_eggo]

You need a 100A breaker.

 

[Supervstech]

It looks like inverter 2 has the high amps, but you show inverter 3's voltage input.
What is the voltage input at inverter 2?

 

[Supervstech]

420W panels should output around 6A max, if 4P is giving 80A, something is wired wrong...

 

[Supervstech]

What size fuses are in the input slots?

 

[Hedges]

420W panels should output around 6A max, if 4P is giving 80A, something is wired wrong...

Or 80A breaker is on output of SCC, in which case program SCC for 64A max.

 

[Supervstech]

Or 80A breaker is on output of SCC, in which case program SCC for 64A max.

Why would there be 4 SCC'S tied to a combiner box like that?

 

[Hedges]

I meant 4p PV strings x 6A each, 24A into an SCC and 80A out is more plausible than the strings tripping 80A breaker themselves.

But I can't follow the wiring well enough to be sure if the breaker is array disconnect, or is separate circuit for SCC to battery.

 

[Hedges]

Looking closer, it appears each breaker is 2, 500V poles in series for 1000V, and is fed by a pair of wires from the two electronic boards. Output is a single wire.

80A is high but not impossible for breaker poles that size. Some brands combine two in parallel; if this was meant to be used that way and isn't, it would trip at 40A. But I think it is meant to disconnect both positive & negative.

Display shows 80A, which I think is SCC output.

Other devices in box say surge arrestor, not GFCI (which is something else that can trip.)

 

[Jazzmonger]

Those graphs are both inverter 2. Each line into the box shows 15-20 amps at full sun so it is hovering at 80amps total.

 

[Jazzmonger]

420W panels should output around 6A max, if 4P is giving 80A, something is wired wrong...

3 panels in series, then 4 of those strings in parallel. That's what 3S4P means as I stated in my opening description.

 

[Jazzmonger]

You need a 100A breaker.

On standard PV wire?? I don't think that's a good idea... However, I'm thinking of running 6 awg to the inverters or 2 pv wires each on +/- to the inverter.

 

[Jazzmonger]

Or 80A breaker is on output of SCC, in which case program SCC for 64A max.

That wouldnt maximize my solar production tho... I'm using all of it as it is.

 

[Jazzmonger]

Why would there be 4 SCC'S tied to a combiner box like that?

3S4P solar panels tied to the combiner box, not charge controllers.

 

[Supervstech]

3 panels in series, then 4 of those strings in parallel. That's what 3S4P means as I stated in my opening description.

Yes... 3S doesn't affect amps, only volts, so 4P is the only factor in amperage, and shouldn't exceed 25A

 

[Jazzmonger]

Yes... 3S doesn't affect amps, only volts, so 4P is the only factor in amperage, and shouldn't exceed 25A

Correct. but the breaker is rated for 80A...

 

[Supervstech]

Correct. but the breaker is rated for 80A...

And it is tripping... which means there is a problem with the wiring.

 

[Hedges]

We see 4 wires into the box.
Does each wire have one PV string? Or multiple strings joined with "Y" cables?
You said each line into box 15 to 20A, which is awfully high for one string.

 

[Jazzmonger]

And it is tripping... which means there is a problem with the wiring.

"with the wiring".... actually i would rephrase. The wire is fine... "How it's wired" is the issue. I think I need to move one parallel string to a different combiner box to balance the loads. The "way" it's wired is causing too much current to flow through the breaker, thus tripping it.

 

[Jazzmonger]

We see 4 wires into the box.
Does each wire have one PV string? Or multiple strings joined with "Y" cables?
You said each line into box 15 to 20A, which is awfully high for one string.

Each wire has one string. No Y cables.