Device to Auto Power 208V Equipment Based on Temperature?

All of the portable units I have seen have temperature control - just set the trip point to above the normal room temperature. They also generally do not autostart if power is lost and restored - so a thermostat in the supply line would not be effective.

Some continue to run the room fan when the desired temperature has been achieved. The power consumption drops to around 50W or less under those conditions- possibly not a significant amount to worry about. However, if it was of concern, a thermostat could be fitted in the unit to stop the fan, or the fan could be disconnected and reconnected to the internal vent fan supply - so it would only operate when the heat pump plant was operational. Unless the unit does have an auto-start on power resume facility, *it* would have to be modified and not the external supply.

Having worked around several mission critical areas, we usually had at least one spare A/C unit installed and ready to use. Like Sue said, just set the second unit to a slightly higher temperature so it doesn't run unless needed. You can add a relay to give a dry contact signal that the emergency system is in use before it can fail, too. if you don't do this, you can be running on the backup system for a long time before anyone notices.

Since this is a server room, you should be able to monitor the room temperature and failure signals, then transmit a message to your maintenance people. You also have extra capacity for extended periods of higher than normal outdoor temperatures.