BeGreen said:
Thanks for the tips and advice. I have discussed the shutdown issue with the electrician. Seems that once the main has been isolated from the grid, that the system could be tickled with a UPS. Would that work?
When I installed my grid-tie system, I had to design it myself because there were no grid-tie kits on the market that allowed grid-down use. Here in NY, to get any New York install-incentives a person is forced to use a NY certified installer - and many are not very skilled and install premade kits only. That was 5 years ago and I assume tech has improved a bit.
In my case, I've got battery backup. That requires the added expense of batteries, and controller-chargers. When the grid goes down, my house and barn automatically revert to the twin inverters powered by the 48 volt battery bank. As soon as the sun is out, the panels charge the batteries, or run my home via the twin inverters, or both. It's seemless. When the power goes down (and it has many times in the past five years) things go on here as if nothing happened.
To install a pure grid-tie only system, all is needed is - panels and inverters. Often those panels are very high voltage and not suitable for ever using with a battery bank. Some are wired up as high as 600 volts DC. If you had such a system, I know of no way to make it truly useful in a grid-down situation. Yes, there are ways to cheat and force the solar DC power to get through the inverters and feed the house AC when the sun is bright. But even so, that wouldn't work early morning, late noon, night, when a cloud came by, or many 24 hour dark days and weeks in the winter.
Solar works by making a lot of power, and sometimes making no power - at different times. So, to work - you must have a way to store the excess when available, and get it back when the sun is gone - to run your house. Grid-tie does that when the grid is "on." Batteries do it anytime as long as they not dead. Our battery bank here can run the house for three days - with total darkness - which has never happened. If it did somehow occur- I have means to use a diesel generator to power a 48 volt battery charger - to prevent the batteries from getting overdrawn.
So, basically - if you are buying grid-tie -but want main components that could be used with battery backup, you ought to keep systems DC voltage at 48, 36, or 12 volts. Note that with a few newer inverter-chargers, 60 volts is also possible. If you buy a bunch of 100 or 200 volt panels - regardless if wired up in parallel or series - it's doubtful you could ever get them to work on a battery-backup system. If you got panels that are no higher then 60 volts each, then it would be possible at a later date.