It has been a long time coming, but I finally pulled the plug on the power co-op. I have long had enough solar power and more than enough inverter power, but battery was lacking and so was buried copper. Then there was the matter of the Round Tuit. I finally got around to it.
Batteries came to me last year. 3000-4000 amp-hours is a good place to be, but for how long? The batteries are strong, but they are about 8 years old. I am hoping for 15 years, but will be ever vigilant for battery opportunities.
There is all kinds of stuff buried in my yard and I am doubtful I can cut another trench without cutting some of the existing pipes and cables, so I sought to repurpose some of what I had. One cable, good for about 100 amps, was bringing DC power into the Zero Export Grid Tie experiment. That had been a successful project, but it just did not go far enough. That freed up the cable, some hardware and 16 golf car batteries.
Ok, remove the 2kw solar feed at the Solar Shed and install a 6 gauge jumper to the AC power bus. That end was done! Now, how to get the power into the house? I do not enjoy crawling under houses or boring holes through walls and floors, so maybe I could use an existing cable. Yes, I could!
Because in an earlier life I was running most of my house on a 5kw inverter, I had installed a lockout so that only one of the two central air units would run at a time. That left a 30 amp line from an external disconnect to the breaker box. With the aid of a very clever mechanism, shown below. I was able to turn my main breaker and that a/c breaker into a transfer switch. All I needed now was a 12′ whip cable to go from the a/c disconnect to the auxiliary power (aka “Generator”) disconnect. Pre-made cables are 6′, so I had to make a trip to Home Depot.
Some of you who are paying attention might note that I only have a 30 amp circuit here. To run the whole house? Nope. Having said that, though, the idea of Code making you put in service capacity of 200 amps and up is overkill.
Another breaker in the main panel has long gone to an “essential services” transfer switch. The load here started out with all the lights and the kitchen. (This was initiated while the house was under construction and a hurricane left the lines down for 4 days. The initial setup was a Trace PS2524 and 8 golf car batteries for backup. No solar.) A few outlets have been added so the TV and other paraphernalia , like a freezer and two more refrigerators can operate. This was all done on a 40 amp circuit, with ease. The two a/c compressors have no connection at all to the house or breaker box, powered directly from the solar shed. Inside, about the only things not on the essential line were the electric range, the air handlers and the laundry room. The only chance of popping the breaker on the new line would come if clothes were in the dryer when the stove was running on all burners. So far, so good. I just have to be careful about asking my wife NOT to cook. If it becomes an issue, I can bore some holes, crawl under the house and pull in a bigger cable.
Another issue to watch in the coming months is inverter capacity. In addition to the house loads, the shop is charging 3 electric vehicles, running power tools and, in the Man Cave, there’s a home theater and more air conditioning. I have two power systems in parallel. A pair of SMA Sunny Island inverters producing 12kw is running the whole house and is the only inverter available to the new transfer switch. Another transfer switch in the Solar Shed lets me connect either the Sunny pair or a homebrew10kw inverter to the essential line. If capacity is an issue, I can run BOTH inverters, one to each circuit, for a total capacity of 22kw. If that should fail, there’s an automatic Kubota diesel generator and a manual Honda generator. The Honda will be living in the space vacated by the old grid tie system. Oh, yeah, and I can always flip back to the grid.
Would I recommend such a screwy setup for you? No. Why do I have such a screwy system? Because it is an accumulation of things that have happened over 30 years, rather than the result of a plan. Capacity increased. Goals expanded. The next phase of work will be to clean it up and make it a bit more conventional.
What I would recommend to most anyone, is to have a transfer switch and generator circuit professionally installed. Make it 50 amps or better. That makes it easy to connect a conventional generator or your new and ever growing solar generator.
Something you need to do if you have solar or a generator is to make use of safety placards. The fire department does not like to spray water on a house full of live electrical conductors. I made some up with a home printer. You can get decal paper or use regular paper and weatherproof it by spraying with clear coat. Something like “House is Equipped With Automatic SILENT Backup Power Generator, Pull Disconnect Around Corner on Generator Shed.” is appropriate for my house.
Two weeks in, I have not needed to reconnect or use the generator. There are compromises in how we operate, such as charging vehicles and drying clothes only during the daytime, but things are going well. I’ll write another time on compromises and you’ll see some of that in other articles, as well.