Boiler running when thermostat isn't calling for heat

[mfreepelletman]

I'm new to boilers but i have an 05 dunkirk oil boiler that will not let my house drop below 66 degrees. I set my thermostat at 60 when we leave the home for work and it is always 66 or 67 when i return home. Obviously varies a little dependent on the temp out side, but never lower than 66. Like i said in the title the boiler runs even when the desired temp is already established in the house. Is this right or is there something i need to look at? I don'y understand why it runs when it is not called on by the thermostat, making the house warmer than i want it to be.

any help would be appreciated.

Thanks Matt

 

[muncybob]

In my case the boiler will run to keep the 60 gallons of water it contains up to the set temperature on the aquastat. The residual heat escape from the boiler will rise from our basement to the living area above and will keep the temps there over what the thermostat is set at esp. on days when the outside air is above 40*. The only drawback to this is the 2nd story bedrooms are sometimes a bit on the cool side since the thermostat has not called for hot water to run through the baseboards. I guess I could try moving the thermostat if it gets to be a problem.

 

[ohbie1]

My boiler runs from the aquastat like Muncybob's. Just about all oil boilers I've seen run this way. The aquastat keeps the boiler water between two temps that one can set on the aquastat.

If you have zone valves, one may be bad, or stuck in the open position. This would allow a slow circulation (thermosiphon) even though your TT is not (calling for heat) turning on the circulator pump(s).

 

[flyingcow]

A simple thought, probably a little numb. Does your t-stat need to be level? I still have the old style w/ mercury. Got to be perfect or it will vary.