Care and Feeding of Inverters
Recently I posted about an inverter issue in which my voltages on the DC side were fluctuating wildly. A bad inverter was ruled out because I could see the fluctuations on either inverter.
The problem corrected itself with no effort on my part, exactly what I did not want to happen. I wanted to have the problem remain so as I went through the process of trying to determine the cause I would know what was making the fluctuations happen.
Since the problem related to the DC voltage fluctuating from a relatively low reading, up to one in excess of the limits and back, with each up and down cycle only taking a second or two the concensus was a bad terminal or connection relating to the cables to and from the batteries. I spoke to several people who are experts and it was agreed the inverters were not defective, but the issue was somewhere in the maze of cables and connections relating to the house battery bank.
In addition to experts from Liberty, I also spoke to Dave Gusdorf (505-938-4095) from Santa Fe who enjoys a reputation as the go-to guy for inverter repairs or rebuilding. I learned a lot.
The most important thing I learned is our inverters need good clean tight connections to and from the batteries. That includes the grounds. I started at the chassis ground post and removed the cables, wire brushed them and the post and removed all the white corrosion that had accumulated over 13 or 14 years of the bus's life.
I did the same thing at the disconnect switch / circuit breaker panel and found that while no connections are what I would describe as loose, they also were not as tight as they could have been. I ended up at the inverters (which are not so conveniently located under the bed) and tightened the connectors where the inverter cables and the cables to the disconnect panel join on a terminal block. They also were not as tight as I would have liked, but they were not loose either.
The final step was as a result of a recommendation by Dave Gusdorf. I opened the inverters and cleaned them out. They both had an accumulation of dust throughout. I expected to see that based on what Dave said. All our inverters draw in fresh air for cooling and over time the dust, lint and airborne particles in the air collect in the inverters. I blew and vacuumed the dust and dirt out and was surprised at how much was actually inside the inverter.
In our conversation Dave recommended I do nothing to the inverters if they are working. Don't replace parts, don't rebuild them, just keep them clean. He did suggest however that I look at what he finds to be the most commonly replaced parts and that is the relays which transfer power through the inverters when connected to shore power. In the case of my inverters they are Potter Brumfield relays, readily available so I now know I can service the most likely service issue with an off the shelf component.
I inspected the contacts on the relays and they looked clean so I buttoned up the inverters and put the bedroom back together.
The probability of doing an inverter repair other than fan or relay replacement is slim. The cost of the boards is $700 to $900 so even if I do the work myself when I use up my replacement boards if one fails I am going to replace inverters. Xantrex is pricing repair parts so high they are pushing people to replace rather than repair.
I have logged my inverter cleaning and I am adding that to my maintenance as a 4 year item. If you can easily access your inverters and can get the cover off easily you may want to consider vacuuming and blowing compressed air on them to get rid of the accumulation of dust and dirt, especially if the bay they are located in has a fresh air supply from the outside and can pick up dust and dirt off the highway.
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