Xantrex Grid Tie Inverters Work Intermittently
I have an 8.5 year old 8kW system with 2 Xantrex GT 3.8 Inverters (3.8kw). One inverter was replaced after about 6 months of use but has been fine since. The installer is no longer in business. I am very handy and have an Electrical Engineering degree but I don't have much experience in this area. The whole array is on the same surface with the same sun exposure in Phoenix, AZ.
Lately I have had noticed that the system is working intermittently. Sometimes one inverter is online producing 2500-2800W (fairly normal value) and the other is "Inverter Offline." Then sometimes the other system works and the other is offline. Sometimes they are both working. Today it was sunny all day, they were both off until around 2pm when one of them started working. The other never did.
Here is what I have determined so far:
1. There are no faults displayed by the unit
2. Both units show ~300Vdc coming in from the solar array on my DVM whether the inverter is online or not. I think this rules out array or wiring issues to the array.
3. Fuses in both units are fine.
4. I have not yet removed the cooling fins to inspect behind those components.
5. I have tried switching them on and off
Any ideas? I find this to be really a peculiar failure mode, and I'm really surprised that it affects both units.