Combiner panel troubleshooting

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GrizzlyAdams

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Marion Illinois
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Solar installation
We have 2MW site that keeps tripping 2 breakers on the combiner panel. I have been trouble shooting this issue for years. The top 2 breakers in the panel trip during spring and early summer. We have swapped the breakers around and confirmed the issue did not follow the breakers, We also moved the breakers up in the panel to create separation from the bottom 8 breakers to try and dissipate heat. I have checked all the wiring and terminations and I cannot find anything of concern, I even repulled new wire from one of the inverters. The last time we were there, we did an infrared scan and noticed B phase on the 2 breaker that keep tripping and wires are hotter than the other phases. I am hitting a mental road block on what could be causing the issue. Any recommendation on troubleshooting would be appreciated. We have another combiner panel onsite with the same number of breakers and and in the same conditions and it is not having any issues.
 
Total guess, but consistent with the information provided: damage to the B-phase bus at those two locations, so the breakers there aren't making a sufficiently low resistance connection to the bus?

Cheers, Wayne
 
I'm assuming this enclosure is outside and exposed. When I have seen this before a logging temperature recorder was used to record the temperature inside at the top of the enclosure at the level of the tripping CBs and compare that to the CB trip times. The trip times correlated to high temps in the enclosure. Leaving the enclosure door open and rigging a shade over the enclosure stopped the tripping. The long term fix was AC in the enclosure and no more approving single vertical columns of CBs in exposed enclosures.
 
Tripping in spring and early summer would suggest it is a combination of high inverter current and high ambient temp, not just primarily ambient temp. Can you confirm that from any monitoring data? Is there any difference between inverters? Did you try moving the inverter conductors to a breaker lower in the panel to see if it follows the inverter (if the wiring will reach)? If it follows the inverter, instead of being related to the breaker position, maybe it is an issue with the inverter. And what conductor sizes and material, and what inverter output current rating are we talking here?
 
Thank you all for the re
wwhitney said:
Total guess, but consistent with the information provided: damage to the B-phase bus at those two locations, so the breakers there aren't making a sufficiently low resistance connection to the bus?

Cheers, Wayne
Click to expand...
I thought that as well, but we have moved the breakers on the bus bar and the issue followed the breakers/inverters.
 
pv_n00b said:
I'm assuming this enclosure is outside and exposed. When I have seen this before a logging temperature recorder was used to record the temperature inside at the top of the enclosure at the level of the tripping CBs and compare that to the CB trip times. The trip times correlated to high temps in the enclosure. Leaving the enclosure door open and rigging a shade over the enclosure stopped the tripping. The long term fix was AC in the enclosure and no more approving single vertical columns of CBs in exposed enclosures.
Click to expand...
Yes, outside and exposed. This is where I was leaning since the issue does not follow the breakers when I moved them around. We will look into rigging up a shade cover or adding manufacture approved vents to the combiner panel.
 
solarken said:
Tripping in spring and early summer would suggest it is a combination of high inverter current and high ambient temp, not just primarily ambient temp. Can you confirm that from any monitoring data? Is there any difference between inverters? Did you try moving the inverter conductors to a breaker lower in the panel to see if it follows the inverter (if the wiring will reach)? If it follows the inverter, instead of being related to the breaker position, maybe it is an issue with the inverter. And what conductor sizes and material, and what inverter output current rating are we talking here?
Click to expand...
All of the inverters are maxing out right around 66KW no real difference between inverters. After looking at the specs here, I think this may be the issue. They are 60K inverters, programmed to max out at 66KW. The output at 66KW is 80amps. We installed #1AL wire which is rated at 100 amps (75 degree). 80*1.25= 100amps for continues use. It does not look like we derated the conductors for temperature or more than 3 current carrying conductors as we do no see over 104 degrees often and each inverter has its own conduit. I am guessing it is reaching over 104 inside the combiner when they are all producing max and we are seeing 95 degree temperatures with direct sun shining on the enclosure all day. We have moved the inverters and breakers around and it seems to stay with the top position breakers. We are going to try and shade and vent the combiner panel and see if that works.
 
GrizzlyAdams said:
I am guessing it is reaching over 104 inside the combiner when they are all producing max and we are seeing 95 degree temperatures with direct sun shining on the enclosure all day. We have moved the inverters and breakers around and it seems to stay with the top position breakers. We are going to try and shade and vent the combiner panel and see if that works.
Click to expand...
Keep in mind that CBs are listed using 40C as the maximum operating temperature, go over that and the trip setting of thermal/mags need to be derated. If it's 40C outside ambient then it's a lot hotter inside the closed combiner in the sun. You can get the temperature derate curves from the CB manufacturer and find out what the actual trip setting on those CBs will be at higher temperatures.
This is why I recommend logging both the temperature inside the combiner and the current through the CB using a logging meter setup to find out if there is a connection to the tripping.
 
GrizzlyAdams said:
All of the inverters are maxing out right around 66KW no real difference between inverters. After looking at the specs here, I think this may be the issue. They are 60K inverters, programmed to max out at 66KW. The output at 66KW is 80amps. We installed #1AL wire which is rated at 100 amps (75 degree). 80*1.25= 100amps for continues use. It does not look like we derated the conductors for temperature or more than 3 current carrying conductors as we do no see over 104 degrees often and each inverter has its own conduit. I am guessing it is reaching over 104 inside the combiner when they are all producing max and we are seeing 95 degree temperatures with direct sun shining on the enclosure all day. We have moved the inverters and breakers around and it seems to stay with the top position breakers. We are going to try and shade and vent the combiner panel and see if that works.
Click to expand...

It wouldn't surprise me at all if they were tripping on temp. Once I had a panel in a greenhouse and it was hot in there. They were having issues with breakers tripping even though nothing was loaded past 80%. As a temporary measure we put some washers under the panel cover to space it off and put some fans on it and that took care of it. Another time, in a grow room inside, I had a lighting panel I designed and installed that had like a dozen three pole breakers for grow lights and they were loaded right at 80%. I never did have any tripping, but boy it must have been close, that panel got hot. IF I could go back I would get a larger panel and leave a space between each breaker. I thought about punching a few 4" holes for ventilation and putting a screen over them, but like I said nothing ever did trip so I never did.
 
pv_n00b said:
Keep in mind that CBs are listed using 40C as the maximum operating temperature, go over that and the trip setting of thermal/mags need to be derated. If it's 40C outside ambient then it's a lot hotter inside the closed combiner in the sun. You can get the temperature derate curves from the CB manufacturer and find out what the actual trip setting on those CBs will be at higher temperatures.
This is why I recommend logging both the temperature inside the combiner and the current through the CB using a logging meter setup to find out if there is a connection to the tripping.
Click to expand...
Understood, thank you.
 
Top position in the panel will be the hottest from convection and also closest to any constant heating from a main above them.

You said you created space below. Perhaps space above would work better? Among other things it could provide better ventilation to carry away the heat from those breakers.
 
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