Combiner breaker tripped mid day

[Greendream]

Today the 63a output dc breaker at the combiner box tripped. The calculators I've ran on my array showed 54A max output. I saw the charge controller with upwards of 60A when i last saw it before it tripped. Is there an explanation for this that I can troubleshoot? We have 120ft of 4 awg cable running from the combiner to the charge controller.

I have 4 strings of 5 panels on my array. It was really hot today and our wire is not buried (just in pvc conduit) so if heat could contribute?

 

[Bud Martin]

What is the spec of the panel?
What is make and model of the SCC?
Combiner box make and model?
Does the combiner box have the circuit breaker/fuse for each string?
Pictures?

 

[Greendream]

What is the spec of the panel?
What is make and model of the SCC?
Combiner box make and model?
Does the combiner box have the circuit breaker/fuse for each string?
Pictures?

Heres the info

Eco worthy 195w panel


Magnum PT100 SCC

Combiner box is eco worthy 6 string -

6 String PV Combiner Box with Lightning Arrester & 10A Rated Current Fuse & Circuit Breakers for On/Off Grid Solar System | ECO-WORTHY

ECO-WORTHY 6 String PV Combiner Box is suitable for photovoltaic grid-connected and off-grid power generation systems. 6 String Configuration, Max current of single PV input array is 10A. Each String Continuous Duty Rated at DC 250V. Single PV input array installs with high voltage fuse, its...

www.eco-worthy.com

Here the breaker that tripped


Thanks

 

[Bud Martin]

Panel Imp is 10.84A as shown on the stciker so 4 strings in parallel = about 43A so it should not trip 63A breaker since 63A is the holding current, it will trip at higher than 63A, so something is not adding up.
BTW, the RED and BLUE wires are really 4AWG wires? They look small.
The box is rated at 60A max but they put in 63A breaker.

 

[Greendream]

Here's a picture of the whole combiner from the website. The internal wires look like 6 awg to me maybe 8. I have 4 awg copper running out to the PT100.

The array was harvesting 3.4Kw when it tripped at 13:18.

 

[MisterSandals]

I have 4 strings of 5 panels on my array

21.6Voc x 5 = 108Voc
11.89Isc x 4 = 47.56A
10.84Im

6 x 10A breakers sounds like maybe an issue? Not sure how this would affect the 63A breaker though...

We have 120ft of 4 awg

A little high for voltage drop (3.13%) for the 4 awg to the SCC but not drastic

 

[Bud Martin]

Do you clamp on DC Amp meter to check the total panel current?
I wonder it may be crappy circuit breaker.

 

[Hedges]

11.89 Isc x 4 = 47.6
NEC calls for wires/breakers 1.56x higher which would be 74A

But we don't expect so much current. Do you have funny illumination, partly clear partly cloudy?
You saw 60A, but that's output of an MPP charge controller? Into what voltage battery.

Do you know what the calculators took into account to come up with 54A?

Wires getting hot [edit: in conduit] would have nothing to do with it.

Troubleshooting, if you have a clamp DC ammeter, measure current from combiner and current of each string.

Picture is combiner on vendor's website. How about a picture of yours?
They show 6 fuses. Any chance you have 4s5p array not 5s4p? That would push it to the limit.

I wonder it may be crappy circuit breaker.

You don't think?
I googled the part number and the only hits I got in English said, and I quote: "Cheap DC breaker"

But I've had issues with my Square-D AC breakers.

I think this type is magnetic-hydraulic, which might not be affected by heat.
But check insulated wire next to breaker, see if it gets hot. Check body of breaker for heat.

 

[Greendream]

Do you clamp on DC Amp meter to check the total panel current?
I wonder it may be crappy circuit breaker.

I have another breaker i bought to build a cutoff switch for the array. I can try it in there if it happens again. First time its happened but the system is only up for 2 weeks now. Still working out the kinks. This was a big problem though and I wanna address it asap.

11.89 Isc x 4 = 47.6
NEC calls for wires/breakers 1.56x higher which would be 74A

But we don't expect so much current. Do you have funny illumination, partly clear partly cloudy?
You saw 60A, but that's output of an MPP charge controller? Into what voltage battery.

Do you know what the calculators took into account to come up with 54A?

Wires getting hot would have nothing to do with it.

Troubleshooting, if you have a clamp DC ammeter, measure current from combiner and current of each string.

Picture is combiner on vendor's website. How about a picture of yours?
They show 6 fuses. Any chance you have 4s5p array not 5s4p? That would push it to the limit.



You don't think?
I googled the part number and the only hits I got in English said, and I quote: "Cheap DC breaker"

But I've had issues with my Square-D AC breakers.

I think this type is magnetic-hydraulic, which might not be affected by heat.
But check insulated wire next to breaker, see if it gets hot. Check body of breaker for heat.

I will get a picture tomorrow during daylight of my combiner box.

I am in a canyon in Colorado no trees or obstructions cloudy at times usually sunny.

Definitely 4 parallel strings of 5 panels to the box as the other 2 strings on the combiner are empty.

I checked the breakers for heat after I detected the problem. I estimated the breaker tripped about 30 min before I discovered it. The whole box was very warm on the outside and all the internal breakers were quite warm too. It was also 95F outside temps.

Heres the array calculator i ran on magnums website

 

[Greendream]

We have 48v lfp batteries. The 60a was read on the SCC so that may have been incoming and outgoing amps?

I will check tomorrow with clamp meter.

 

[Hedges]

6 x 10A breakers sounds like maybe an issue? Not sure how this would affect the 63A breaker though...

"Max Input Current of Single PV Array: 10A"
Fuse holders is what I see, and based on current rating his panels ought to have 20A fuses but label doesn't mention.

We have 48v lfp batteries. The 60a was read on the SCC so that may have been incoming and outgoing amps?

I will check tomorrow with clamp meter.

Assuming SCC is MPPT, it would be outgoing amps.

At full output, 90V 43A from panels I calculated 65V 60A at battery. But that's above LFP max charge voltage, so lower voltage at battery and lower current from panels. Even less reason to trip breaker.

A PWM SCC would have same current in and out, but no current boost.

Can't think of any way for the array to deliver enough current to trip a good breaker. Bad breaker or poor contact with wire heating it, if they are thermal breakers.

I had a 100A QO breaker that was tripping well under 70A. Maybe it had degraded from prior operating conditions.

I got a 63A transfer switch (interlocked 2-pole breakers) from an eBay vendor out of China, but it started buzzing and I didn't trust it, replaced with a Square-D interlocked breaker box.

I've got some Schneider 63A DIN mount breakers that haven't given me any trouble, but I haven't stressed them.

 

[SpongeboB Sinewave]

Maybe the 63A breaker is defective ? Maybe you had an edge of cloud event that temporarily raised the power much higher momentarily and the PT100 took time to respond to that ?

Another but more rare possibility is that the PT100 back-fed the array from the battery ? I do think the PT100 is basically a synchronous buck converter which would be capable of doing this in a perfect storm. Less likely but possible.

 

[Greendream]

Here's a picture of the cable I'm using for the PV run off the combiner to the SCC. Bought online on Amazon, Windy Nation supplier -

Amazon.com

Here's the inside of my combiner box -




Here's a spare breaker I bought -

 

[Hedges]

Polarity of your 63A breaker ...

Polarized DC breakers can only interrupt fault currents at full voltage successfully in one polarity. I believe that is with the positive source connected to the terminal labeled with "+".
But what can you do about bidirectional current??
In normal operation, PV panel positive is more positive than SCC and battery positive. Vendors have said to connect PV positive to the "+" terminal of polarized DC breaker.
If PV array was shorted, and SCC was faulty so backfeeding from battery, that would be opposite current flow direction.

What I haven't heard of was the magnetic trip of a breaker behaving differently for different polarity (just interruption of current being poor when used backwards.)

Maybe the direction of current flow in your circuit causes breaker to trip below its rating?
Yours is backwards from what's shown in vendor picture. Did it come with breaker already installed?

 

[Hedges]

You have fuses to protect individual PV strings, which is better than polarized breakers.
What fuse rating?

6 installed, but can see two MC connectors not connected.
Minor improvement suggestion - you have all four PV connections on left. Three feed current into left side of busbar, then there is wire to 63A breaker, then one PV connection to right side of that wire. Suggest moving one of the 3 connected strings on left to the right. That way, 20A fed from left and 20A fed from right, instead of 30A from left. Reduced current through cross section of busbar.

That's the red positive wires. Trace the blue negative wires, possibly rearrange order in busbar to match order of MC connectors so they also follow same current distribution.

 

[Hedges]

Spare breaker is a different brand. Good chance it behaves differently. First guess is bad breaker.
When using it, note its + and - are in different location.

 

[Greendream]

Polarity of your 63A breaker ...

Polarized DC breakers can only interrupt fault currents at full voltage successfully in one polarity. I believe that is with the positive source connected to the terminal labeled with "+".
But what can you do about bidirectional current??
In normal operation, PV panel positive is more positive than SCC and battery positive. Vendors have said to connect PV positive to the "+" terminal of polarized DC breaker.
If PV array was shorted, and SCC was faulty so backfeeding from battery, that would be opposite current flow direction.

What I haven't heard of was the magnetic trip of a breaker behaving differently for different polarity (just interruption of current being poor when used backwards.)

Maybe the direction of current flow in your circuit causes breaker to trip below its rating?
Yours is backwards from what's shown in vendor picture. Did it come with breaker already installed?

The whole combiner box was pre-wired with the breaker in it's correct position. We initially had some problems with our cutoff switch (doesn't work or wrong rating? It never worked.) and during the troubleshooting we found that flipping the breaker and disconnecting the cutoff in-line got the voltage to the SCC. It's been that way ever since, and suspected the breaker may be defective.

I did move one of the strings from the left side to the right. I've been watching the PT100 like a hawk this morning. Partly cloudy but seeing ~44A max pulling from the panels with 2.2Kw around 88-90V.

Tonight when the sun goes down I am going to shut off everything and remove the old breaker and install the new one, then back to watching like a hawk until I can trust the setup.

Unfortunately the only clamp meter I have is AC current only, so I have to run to the hardware store and see if they have a DC clamp meter, otherwise it may be until next week to have one delivered.

Here is a picture of the fuse up top and the breakers below for the strings -
(EDIT: Those white 20A breakers are all very warm to the touch)



Some pictures of the PT100 tt's at around 11AM, full sun


Parallel box for 3pc Llama 48v batteries - Guessing that's AMPS inbound since it seems to have that offset based on the amp draw from the inverter powering AC loads.


Thanks for everyone's help and suggestions. If there is anything else to look for I am all ears.

 

[Hedges]

Home Depo and Lowes have Klein, maybe Fluke. The Klein in stock at home depo didn't do DC amps, one on website did.
I bought the Harbor Freight 1000A model. Price was $100, resolution was 0.01A not 0.1A like some, better for reading PV strings when they are producing low current.

Moving string connections won't address this issue. I just like to feed a busbar from both ends, minimize current through its cross section.

Those aren't 20A breakers, they are fuse holders for up to 20A fuses.
They should not be getting hot at half rated current.
They are touch-safe, but not for interrupting current. With 63A breaker off, they can be opened.
Two are not connected to PV, so you can open them right now. See what fuse is inside. Any documents for PV panels recommending maximum fuse size? My math came up with 18.5A minimum per NEC.
It may have been shipped with 10A fuses in 6 fuse holders. If so, on the hairy edge of blowing, and might explain temperature rise.

The black things are anti-backfeed diodes (not breakers). I don't believe there is usually a need for diodes. But if polarized breakers were used (which can't interrupt current when backfed) the diodes would protect them. With fuses, I don't believe diodes are necessary or beneficial.

Flipped breaker shouldn't have made a difference in continuity. It does affect ability to interrupt current at higher voltage - there are videos of breakers catching fire when used backwards. Yours should only see current one direction unless SCC fails and backfeeds from battery, into a PV array which is shorted (two independent faults would be necessary.)

It is possible breaker will carry more current without tripping if oriented as originally delivered. Depends on how "magnetic" works in those things.
I would try putting it back in original orientation.
Other thing to try is the other brand breaker.

Magnum displays both PV and battery parameters - nice!
2400W PV at 84.5V = 28.4A

Battery voltage agrees with Llama. Kind of low at 2.9V per cell, guess you're drawing current?

 

[HRTKD]

The polarity of the breaker caught my eye too. Switch it around and see if that takes care of the problem.

 

[SpongeboB Sinewave]

Yes, polarity can sure matter if it is not a non-polar breaker.