:. Project / Dorm Thermostat

Welcome to Towers dorm at Georgia Tech.  This is the oldest dorm on campus and, at the time, was dorm that hadn't been renovated in the longest.  Each room had a heating/cooling unit, but this aspect was somewhat centrally controlled through a unique system, very much like a radiator as illustrated below.

Here the brown represents the building, the gray represents a hall and the blue represents water pipes.  Hot or cold water (depending on the current weather) was piped around the outside of the building.  The wall "air conditioning/heater" units simply had a fan that turned on to various settings, blowing air past these pipes to heat or cool your room.  A few fortunate members of the hall were lucky enough to have fully functioning wall units.  However, ours only had an "on" (full on) and an "off" (full off).  If it was cold in your room and you left it on (essentially high heat), in the morning you would be sweating.  If it was warm and you left it on (essentially full AC), in the morning you would have icicles mounting on your eyebrows.  Something needed to be done, and there were engineers in the room to get the job done.

We bought a thermostat online for about $10, and a DC power supply and relay at Radio Shack for about $10.  A double pole throw switch was pulled out of some old electronics.  The thermostat was run through this switch to determine heat/cooling settings and was run on to the relay.  This kick started the fan if the temperature dropped too low/got too high (again, depending on the throw switch).  It was a rather effective way to maintain a pleasant temperature, and well worth $20.

Here you can see the thermostat up against the wall on the right, running into the wall unit.  And here's a close-up of the unit

After the year was over and it was time to clean up and leave, we just snipped the wires, shoved them back into the wall unit, and it returned to normal operation.