Hello Neil, YES, indeed! It does sound like it's operating correctly . I don't think I'm explaining myself correctly. Let's see, I'm looking at a aquastat that only has a high limit wheel, no operating range. It's got me talking to myself. Boiler temperature does not go higher than 120*. I remove the circulator from the circuit and hook it up manually to 110V. Now, with the circulator out of the circuit, the boiler temperature reaches high limit. Ok, I run the circulator manually and the temperature drops to 120* (ok) but it stays there. Hmmmm. I want the circulator to turn off at the set point on the thermostat and I want the burner flame to stay on until the limit is met. Eventually I want to circulate 190* water. He only gets 120* water.