Not sure how long this has been doing this, but I just noticed that the Taco circulator pump on my home oil boiler is constantly running even though *none* of the 4 zones (3 heating and 1 domestic hot water tank) are calling for heat.

The boiler was just cleaned last week, but I can't say it has been running since then, or if this started prior to the cleaning.

Either way, I would expect the circulator pump would stop running if no heat is being called for, and the water tank is not calling for heat.

Any thoughts on what the problem might be, or is this normal behavior?