Last time I wrote of dealing with one of two recent issues that have come up in my system. Michael C. wrote to me regarding an alternative to the water heater dummy load to test or calibrate inverter power. He pointed out that the air handlers—the box in the hall closet– of heat pump and a/c systems usually have a big resistive heating coil built in. When systems get replaced the air handlers get chucked, except maybe the A coil, which contains copper. An old air handler or two could make a dandy air-cooled dummy load and maybe even for free! Add the power controllers from ebay and an ammeter and you are ready to burn some kilowatts. Thanks for the idea, Michael.
The other problem I mentioned was that the slave inverter of my pair of Sunny Island 6048 inverters was slamming off and on when the temperature got around 27 degrees or below. These were bought at auction with no warranty, so I am on my own, here. Intermittent problems can be maddening. When I worked in computer service I might drive across 3 states or fly across the country only to find things running just fine when I got there. You can’t fix it when it ain’t broke.
To that end, I’d try to break it. Computers used to be real fussy about temperature, so I might hose down the circuit board with freon or a heat gun to see if that would affect it. Or maybe start wiggling cables. This is where I started on my inverters.
After being disappointed by a lack of error codes in the built in diagnostics, I pulled the covers on both inverters. The inverters are in a cabinet that barely allows the covers to be removed, so it involves a prybar to deflect the cabinet a wee bit. Naturally, the power was disconnected as I looked for dark spots on the circuit boards and took a wrench to the huge DC power cables coming in from the battery bank. No problems there. I unplugged and replugged every connector to exorcise any minor corrosion that might be there.
Something was missing, though. It appears that there are components on the back half of the chassis and it looks like you can only access this side if the entire inverter is removed from the cabinet. While I admire the packaging effort that DC Solar went to in designing this system, it has some maintainability issues. I am NOT going to take those inverters out unless they are stone cold dead. I noted that the circuit boards have 2 connectors marked FAN and I suspect that neither fan is working on the master unit. The fans are on the back side, naturally. There is a hot smell when the generator is running to equalize batteries, I suspect as a result of no fans.
I can deal with that to some degree with external fans. Furthermore, the unit derates itself if it gets too warm, so it isn’t hurting anything.
As for the principal issue, 27 degrees does not happen a lot in Florida. I think we have had 2 nights at or below that, so for now, I will just toss a shipping blanket over the outer cabinet to hold in the self-generated heat a bit or even put a small heater in the cabinet…even a light bulb.
I know that sounds like a cop out, but there’s the old adage, “If it ain’t broke don’t fix it.” Yes, I know it is broke, if only a little bit, but it could be a lot worse. The oft-ignored motto of the medical profession is, “First, do no harm.” Getting those mostly working inverters out of that tight cabinet would provide all sorts of opportunity to do inadvertent harm and those are really expensive inverters. In the meantime, I will keep watch on the forums and see if someone comes up with a solution. Sending the inverter to the factory with a note that says it won’t work below 27 degrees will not likely result in a fix and will result in lots of postage for a heavy package that might get even physically broken in shipping.
So let’s modify the old adage. If it ain’t really, REALLY broke, don’t fix it. (Unless it is under warranty.)
–Neal
