I have a Dunkirk oil-fired boiler, with 2 heating zones. My question is regarding the temperature. I have been doing a lot of reading on this forum and it seems that a temperature over 190°F is rare. Well, my boiler always heats up past that, to about 210 or 220. The pressure is always consistent, around 16-18 psi. Recently, sometimes after someone takes a shower, popping inside the heating pipes can be heard, which I thought was odd because the hot water pipe does not make noise. The aquastat (L8124) is set at 160/180 with a 20° differential. Is any of this incorrect? Thanks.

 

Some overshoot is normal due to residual heat after the burner shuts off but 30-40º is a bit much IF the gauge is accurate & many are not. If you have access to an accurate themometer attach it to the heating pipe as close to the top of the boiler as possible & insulate well. You can also use an infrared. After the burner has been off for a few minutes compare your thermometer to the boiler gauge.