Hello -

I live in a condo and have what I believe to be a single pipe hot water heating system. For a week now I've noticed that no matter what the thermostat is set to, the temperature is a constant 21ºC. Also, one always hears the water circulating through,w hich I normally just hear when the heat is turned up.

The thermostat is an old style one, so just a small square box with a thing at the bottom that you push from one side to another. When you open it up, there's a glass bulb with mercury in it and a red and yellow wire, eaach connected to a screw. I've managed to get the screw for the yellow one off, so have disconnected that wire, but a few hours later the heat is still on.

Any other thoughts or suggestions? Let me know if there's additional info that I might be able to provide as well.

Thanks,
Barbara

I've now disconnected both the red and yellow wire. You can see a photo of my current thermostat (Honeywell) condition here:
https://picasaweb.google.com/lh/photo/N-LcHLpS6EVAculyZ6J-oTSLUyA92p5P_LrvrbX6AAY?feat=directlink

I've now disconnected both the red and yellow wire. You can see a photo of my current thermostat (Honeywell) condition here:
https://picasaweb.google.com/lh/photo/N-LcHLpS6EVAculyZ6J-oTSLUyA92p5P_LrvrbX6AAY?feat=directlink

Ok, in efforts to kill the heat, I've taken the entire thermostat off the wall. The water is still running though and no signs of it cooling down yet.