Solar Systems

[Lightspeed]

Cheers Nix,
I forgot you are an Alarm specialist.

Currently the whole thing is powered from 220v through a switch mode PSU down to 12v. The main control unit having its own internal backup nicads that will keep it live for 6 hours or so in event of mains power failure. Using an 5 in relay in the mains driven supply line, I'll be able to set it to fail-safe to the 12v PV system. So, while we have mains power the alarm runs from that. Only of we suffer a power cut will the PV derived backup power kick in. If we go grid down for an extended period, we'll wheel out additional generating capability to keep supply and demand balanced

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Oops that reads wrongly.

The relay will be powerd by 12v that comes from the PSU. If that voltage fails the relay drops out, connecting 12v from the PV storage batteries. When mains power is restored, the relay is reenergised and power to the alarm automatically switches back to the mains driven source