Hey folks. I've been beating my head against the wall for months on this problem. I have a small commercial system with 2 3ph 208v SolarEdge 43.2k's installed. The type with 3 inverters plugged directly into the Solaredge head unit through their own cabling. I don't think my issues are SolarEdge related, but rather heat related. The entire setup is located inside a semi conditioned electrical room inside a building. It's always warm in here, but it's also never 100deg ambient, it shares a small Mini split with the maintenance closet next door separated by a thin wall.
There are 2 of these inverters feeding a 400a SquareD MLO Load center, each inverter on it's own 150a breaker. 1/0 copper conductors to each inverter, about 5-10 feet from the load center. Load Center is being fed by a fused AC disconnect w/ 350kcmil, to a CT cabinet, eventually going to the point of interconnection on lugs in a GE meterbank extension. Never had any issues at all with any equipment south of the Disconnect, it's just the inverters behind the load center that are tripping breakers. There are 0 other devices other than the inverters installed in the load centers.
Every time the system really ramps up and starts producing, one of the inverters trips one of the 150a breakers. It only does it when the systems are both producing at max or close to it. I thought it could have been undersized AC Conductors, but the 1/0 @75deg C should have enough to handle a 120a max continuous load. I've tried replacing one of the breakers. I've moved the breaker within the load center to a new spot on the bus bar to create more space between 150a feeders. I had a local breaker shop test the breakers and they seem to bench test fine on the instantaneous trip curve, however they couldn't test temp related tripping. I thought about upsizing conductors and moving to a larger ampacity breaker, but the load center is maxed out on a 150a branch circuit breaker so I'm stuck with 150. I've tried isolating the issue to one inverter, I've tried isolating the issue to one specific breaker, none of it seems to follow any pattern. I've disassembled the lugs on the breakers and cleaned everything and reassembled. I've meggered the PV AC conductors and they're in great shape. Looking at SolarEdge logs the voltage/current/frequency all look great, until one of the units just shuts off. I've contacted Solaredge tech support and they've looked at the same logs I am and are also stumped.... everything looks great until the breaker just trips. I even got them to replace one of the head units, which didn't effect the issue at all.
Struggling for answers I've turned to thermography. I just picked up a decent handheld IR Camera and tested looking for temp deltas anywhere in the equipment. The system overall was producing about 30% of capacity at the time because of clouds and it being December... but the conductors stayed rock solid at just barely over ambient for as long as I let both inverters run. I'm positive the system will stay on for months in December because it's not producing enough current to heat up the equipment. I'm sure it will tell a different story when it's producing closer to max power, but it was pretty defeating not seeing a smoking gun or really any sort of temp deltas anywhere in the system. The control board was the hottest item in the whole equation at about 90 degrees, so clearly when I was testing heat was not an issue.
Everything in this reads undersized AC conductors to me.... or a high resistance connection somewhere. I just cant find it. I haven't replaced the AC Conductors yet, that may be the last step before throwing up a real hail mary and possibly replacing the load center. FYI I'm using a 1 hole compression lug for AC conductors at the inverter, crimped with a 10ton crimp tool. If it had been a torque or a crimp issue I think I would have seen it on the IR gun.
Anyone have any other ideas at all? I'm totally at a loss here.
There are 2 of these inverters feeding a 400a SquareD MLO Load center, each inverter on it's own 150a breaker. 1/0 copper conductors to each inverter, about 5-10 feet from the load center. Load Center is being fed by a fused AC disconnect w/ 350kcmil, to a CT cabinet, eventually going to the point of interconnection on lugs in a GE meterbank extension. Never had any issues at all with any equipment south of the Disconnect, it's just the inverters behind the load center that are tripping breakers. There are 0 other devices other than the inverters installed in the load centers.
Every time the system really ramps up and starts producing, one of the inverters trips one of the 150a breakers. It only does it when the systems are both producing at max or close to it. I thought it could have been undersized AC Conductors, but the 1/0 @75deg C should have enough to handle a 120a max continuous load. I've tried replacing one of the breakers. I've moved the breaker within the load center to a new spot on the bus bar to create more space between 150a feeders. I had a local breaker shop test the breakers and they seem to bench test fine on the instantaneous trip curve, however they couldn't test temp related tripping. I thought about upsizing conductors and moving to a larger ampacity breaker, but the load center is maxed out on a 150a branch circuit breaker so I'm stuck with 150. I've tried isolating the issue to one inverter, I've tried isolating the issue to one specific breaker, none of it seems to follow any pattern. I've disassembled the lugs on the breakers and cleaned everything and reassembled. I've meggered the PV AC conductors and they're in great shape. Looking at SolarEdge logs the voltage/current/frequency all look great, until one of the units just shuts off. I've contacted Solaredge tech support and they've looked at the same logs I am and are also stumped.... everything looks great until the breaker just trips. I even got them to replace one of the head units, which didn't effect the issue at all.
Struggling for answers I've turned to thermography. I just picked up a decent handheld IR Camera and tested looking for temp deltas anywhere in the equipment. The system overall was producing about 30% of capacity at the time because of clouds and it being December... but the conductors stayed rock solid at just barely over ambient for as long as I let both inverters run. I'm positive the system will stay on for months in December because it's not producing enough current to heat up the equipment. I'm sure it will tell a different story when it's producing closer to max power, but it was pretty defeating not seeing a smoking gun or really any sort of temp deltas anywhere in the system. The control board was the hottest item in the whole equation at about 90 degrees, so clearly when I was testing heat was not an issue.
Everything in this reads undersized AC conductors to me.... or a high resistance connection somewhere. I just cant find it. I haven't replaced the AC Conductors yet, that may be the last step before throwing up a real hail mary and possibly replacing the load center. FYI I'm using a 1 hole compression lug for AC conductors at the inverter, crimped with a 10ton crimp tool. If it had been a torque or a crimp issue I think I would have seen it on the IR gun.
Anyone have any other ideas at all? I'm totally at a loss here.