I put together a few simple devices to turn the A/C back on in the event of a power loss. It persistently tries to turn the A/C unit on, and won't stop until it sees that the A/C unit is turned back on.
Parts you'll need:
Christmas light day/night timer - $15
MK111 interval timer - $15
12v dc power adapter - $?
12v dc buzzer - $3
spare wire - $?
You'll also need some basic soldering skills to put the MK111 interval timer kit together and solder a few extra wires in the remote control, and the Christmas light timer.
Step 1: Hacking the Lighting Timer
This is your typical "Christmas Light" timer. It has a "Dusk to Dawn" feature. When it senses there is no light, it will power the plug at the bottom, and when it sees light, it turns the plug off.
First I ripped out the light sensor (photocell) and soldered an extension for it so I could attach it to the A/C unit. The other reason to rip is out was that I needed to isolate it from any outside light.
Then I taped the photocell to the "cool" LED on the A/C unit. This LED light is only on when the unit is on. I used black electrical tape to make sure it could only see light from that LED. Then I used the stickiest tape that I could find, and taped over that. I also taped the wire down for a short distance in case somebody snags on the wire.
Once that is complete, this circuit will only turn on if the A/C unit is turned off. And once the A/C unit is turned on, the plug will turn off.
Next is the device that turns the A/C back on.
Step 2: Making the Interval Timer
I bought it from www.cs-sales.net. The model nubmer is MK111. $6 for the kit, and $7 shipping.
This kit has an adjustable 555 timer in it that can click 2 wires together anywhere from 2 - 60 seconds. It's powered by 12v dc. It comes disassembled, and you'll have to solder it yourself. I took a 12v dc power adapter from an old set of HP speakers to power the device.
Next we need to wire the interval timer to the remote control.
Step 3: Wiring the Remote Control
Then take the other end of those wires and insert them into the relay portion of the timer.
Step 4: Putting It All Together
Now when the power goes out, the Christmas light timer will see that the LED on the A/C unit is turned off, and will activate the interval timer circuit.
The interval timer circuit continuously hits the power button on the remote control.
Once the power comes back on, the remote will turn the A/C unit on.
When the photocell sees that the LED light on the A/C unit is on, it will turn the interval timer circuit off.
A couple days after I finished putting it all together I realized that I can put a 12v buzzer in the system. I picked up a 12v 15ma 75db buzzer from Radio Shack. Now when the Interval timer circuit turns on, it makes an annoying buzz to alert me that it is running.
Step 5: Possible Problems and Future Plans
The batteries in the remote could die. Just make sure you have a fresh pair every now an then. I would have wired the relay switch directly to the power button on the A/C unit, but I would have to void the warranty on the A/C unit. I figured it would be easier to unsolder the wires off of the remote, should I ever need to get the A/C unit replaced under warranty.
And finally, if the photocell were to fall off or get pulled off, and it was dark in the server room, it would turn the A/C unit on and off every 60 seconds. Probably not a good thing for the unit, so make sure it is secured well! I installed the buzzer because of this reason. I would like to get the interval timer to go off every 10 minutes instead of every minute.
If anybody knows what component of the Interval timer I can adjust / hack to get the time longer, please let me know in the comments! I assume you 'up' the resistance in the potentiometer, but I'm not 100% on that.