Not sure if this is the correct forum, as my heating system isn't actually a steam system, just a standard hot water radiator system.

Anyhoo, I have a 6yr old williamson oil fired furnace (single zone). My high limit is set to 180, my low limit is set to 160. Diff is set at 15. There is a hot water coil installed. Now on to the problem (if it actually is a problem):

If no heat is called for, the furnace seems to work as normal, with indicated temperature never exceeding 180, including when we are using hot water (for the dishwasher, shower, etc.). However, if there is a call for heat, the furnace turns on normally, but will continue to burn well past the 180 high limit as long as the call for heat is still on. It will, however, turn off as soon as the call for heat is gone (when the house temperature setpoint is reached and the circ pump turns off, or if I simply turn the thermostat off). I've seen boiler temps as high as 210. Is this normal?