setback thermostat with freeze protection program

We are looking for programmable setback thermostats for our radiant hot water heating system in our building. Freeze control is the real driving requirement, as the rads are on the outside cold wall of the units, and have a tendancy to freeze solid with the resulant mess in winter.
To prevent that, a program that temporarily cycles the heat on is needed (for instance 1 out of every 30 minutes), in addition to the normal freeze control program that is based on ambient air temp. The heater control is a normally closed (NC) circuit, where an open circuit causes the valve to open and hot water to circulate.
Can anyone point me to programmable thermostats with all of these features?
Any help much appreciated.
Barry
Cross posted to alt.hvac
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