Pv combiner box keeps throwing 80amp breaker

[Bud Martin]

Does the body of the breaker get very hot at full load?
BTW, What is the spec of the panel?
You have 80A breaker and you are pulling less than half of the breaker spec, may be defective breaker, I see that has a link that joint the breaker handles together, I wonder if you can remove the clear plastic linker that join the breaker for the positive and the negative breaker together and see which one will trip.
If you have clamp-on DC Amp meter with peak hold reading then you use it to monitor the current to see what you get.

 

[Jazzmonger]

I'll check tomorrow at peak production... it's on the down swing of production right now - 6:30pm. I'll also measure the actual DC current on each leg of the combiner box inputs at peak product (1pm or so) as well as the output.

canadian solar 420watt panels.

 

[Hedges]

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.

After combining (inside box and outside), wire needs to be heavy enough for whatever you're putting through it.
If 80A delivered, need 100A breaker and wire thick enough for 100A ampacity.

We run higher voltage, lower current, where possible (when SCC tolerates
it.)

Each wire has one string. No Y cables.

But the panels are rated 9A. How do you get 15A to 20A on a wire fed by one series string?

We still can't figure out how four, 9A strings in parallel deliver enough current to trip 80A breaker.

 

[Jazzmonger]

westill can't figure out how four, 9A strings in parallel deliver enough current to trip 80A breaker.

I agree. It's a head scratcher. Let me get some real world, hands on data measurements tomorrow and report back with more info.

jeff

 

[Hedges]

Searching part number of breaker, haven't found same one, but other brand a bit different ratings:

Circuit Breaker - JB1Z-125 DC Mini Circuit Breaker

Appears to be up to 220VDC per pole and up to 125A per pole. 80A is one available. Two poles for 440VDC.

I thought your breaker was supposed to be 500V per pole (so two in series is 1000V), and 80A/pole.
Or maybe that is that 1000V with all 4 poles in series? That's how it is used. Two in series on positive, two in series for negative.
OK, in line with the other I found.

But supposed to handle 80A, apparently tripping near 40A from four strings in parallel.
Can you explain 80 to 100A reported by upper chart? Is that output to battery?
Lower chart MPPT 1 has pulses going as high as 80A. Why does it jump around so much?
I wonder if it has capacitor charged to PV voltage, which it dumps as brief high bursts into battery, possibly exceeding breaker limit. Ought to be smooth.
Can you measure PV string and combiner current, e.g. with DC clamp ammeter?

 

[Jazzmonger]

Can you measure PV string and combiner current, e.g. with DC clamp ammeter?

Will do tomorrow.

 

[Shimmy]

To me it sounds like you have a loose connection on the 80A breaker. Check factory and field terminations on all connections.

3S/4P is going to give you a max of 135V / 38A. Measure your voltage and current at the combiner to validate. You should not be able to measure 20A on any of the incoming PV feeds; if you have 20A then the string is not wired 3S.