I didn’t find any relays for $10 –$ 15 which would delaystart up when all power is out but I did find an Omeron G3VM61A1 solid state two pole single throw relay rated for 60 Vac/dc, 500 ma for $2.15 (Mouser.)The A/C compressor relay drawsless than 300 ma at 27 volts AC, so there is plenty of headroom. I added a snubber circuit for protection fromthe compressor relay coil.

I spent more time I care to admit trying to figure out howto sense a power out condition, when the power was out, without batteries. Thenit dawned on me that all I needed to do was wait until power is restored, have along start up process in a PIC, and then send a pulse to a latching relay. I use the second pole of the above SS relay tolatch it on. When the power goes out,the relay opens, and must wait for a pulse from the PIC to close again. I use 3pins to select the delay time with a jumper, 4, 4 ½, or 5 min.

So far it works fine. It has been tested by 4 actual poweroutages and several 2-3 second power “blinks.”