http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=3191&item=3190828174&rd=1

With a 24V power supply through the switch on the above controller and to this valve:http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=20598&item=3191254859&rd=1

The prices on ebay for these items are quite cheap.

Jacob

: : Do these valves open/close based on temperature? Could you point me to an exact valve. I can't find anything in the link you gave me.

: You use controller with a temerature sensor that you attach to the line you want to monitor. How you attach the sensor depends on the type you buy. It could be a surface mount or immersion probe. Depends on how much you want to spend, how large the system, and how critical is the accuracy of the probe.
: My thoughts for you, provided you want to do this yourself, is to go to a HVAC supplier like Johnstone. They would have everything you would possibly want for this system.

: Go to this site for a location near you.

: http://www.e-johnstonesupply.com/main/selectstate.asp