Charles, Dave: you are both right . X10Pro support at first gave some conflicting advice on this but then retested and yes it reverts back to the previous state it was on. Any brand/model # on the 24 volt latching relay and 120 volt coil?
Thanks.
Lest we've confused you about this: The relay we're talking about for your application will be a regular DPST-NO (Normally Open) relay with a current and voltage contact rating sufficient for your Air Conditioner but with a coil designed to pull in with 24 Volts. It is NOT a "latching" relay, but a normal relay wired so as to keep itself turned on once it is actuated by a momentary contact and as long as the power is on. A lot of suitable relays will have DPDT contacts, which is fine. The 120 V coil Dave mentioned was for a different application.
BTW, this assumes that your Air Conditioner runs off 120V single phase. If its a 230V unit you would normall want to switch both hot leads to it, and would therefore require a THREE-pole relay.
There are lots of relays that will fill the bill; the usual problem is how to connect to them and how to enclose them so someone won't get zapped. Quick connect insulated connectors that you crimp to the wires usually work well for relays which have those terminals.
Take a look at Magnecraft W92S7D22-24 in their catalog page at
http://www.magnecraft.com/products/e104_sec1_pg40_42.pdfIt's got 30 Amp, DPST-NO contacts and a 24VDC coil. Quick connect terminals and a mounting flange. It's listed in a July 2005 Mouser catalog I have as Mouser stock number 528-92722-24, $8.74 + S&H. (Price is probably different now - check on-line at
http://www.mouser.com) You'll still need to put it in an enclosure of some sort and acquire a 24VDC wall-wart power supply and a UM506.
Disclaimer: I suggested a part out of a catalog which looks OK to me, but I'm NOT a licensed engineer or electrician and it may be totally unsuited for your application. If you're not familiar with wiring and safety practises for power line work, please consult a licensed electrician or someone with experience.