Solar PV controller - automatic fall back to mains

RobertAndrew

I have a small Solar PV installation with an MPPT, two batteries and an inverter supplying my office. All is well but with the bad weather there have been occasions when the batteries run out as there is insufficient solar to charge them. When this happens the Inverter cuts of nd the office has no power. I would like to have an arrangement such that when the solar power runs out the system fall back to the mins with no break in supply to the office. Clearly this could be achieved by a fall back to a supply (from the mains) to feed into the MPPT; or charge the batteries; or a supply to feed the inverter; or a supply to take over from the inverter output (when it cuts out).

I have been looking at Solar PV control systems and there re many that fall from the mains (grid) to solar PV with batteries, but I can't find any that fall from the solar PV installation (supply) to the mains (grid). Can anyone help by suggesting a suitable design and supply for the necessary kit?

graememk

I've a way to do it.

Basic option, just a 4p 2nc2no contactor.

Solar keeps the contactor enabled if that power fails, it falls back to the grid, almost instantly.

More advanced, the grid keeps the contactor enabled but another smaller contactor (nc, normally closed) interrupts this and keeps the contactor off until the shed solar fails.

Example contactor

https://www.electricalwholesaler.ie/Products/SwitchgearFuses/SwitchgearDistribution/ModularContactors/EatonModularContactor24884925A4P2NO2NC/

Wiring diagram from the sofar me3000sp where I got the idea from.