From an email:

''Hello, purchased old home, hot water heat from old radiators, honeywell round thermostat, need some advice. Heat wont shut off, happend last year, worked after changing thermostat, turned up the heat from 65 to 70 but is higher and doesn't shut down, I switched off breaker disconnected the two wires at the thermostat put breaker back on and still turning on and off - I then left these disconnected and disconnected the red wire at the relay and the unit did not come back on until I reconnected the red wire to the relay. HELP PLEASE. Dont know if this matters but my hot water maker by amtrol runs off the furnace also. I am sorry to bother but it is cold, i am broke and I have a little one at home. Please help.

It sounds to me like the relay is sticking. Try giving it a rap with a screw driver handle while the heat is on. If it kicks off, replace the relay. You should also check the thermostat on the hot water. It could be stuck on.

There are other here that maybe able to give a better answer than I can.