Why do I hear my oil furnace running if it's summer and the heat is off?

Question

My water is not heated by oil, and the furnace gets hot although none of the heaters around the house give off any heat.

Answer 1

My gas furnace turns on the fan to circulate air through the house if the temperature gets too high. It could be just the fan and its not actually burning any oil to produce heat.

Answer 2

If it also heats your water, it will go on to maintain the hot waters' temperature.

Answer 3

If you are SURE it isn't heating your hot water (a "summer-winter hook up"), then it is probably just maintaining a boiler temperature so there will be less of a lag when the heat does come on.

If that's the case, shut it off for the non-heating season and save very expensive oil!  There's probably a switch near the unit, sometimes a red-plate switch away from it somewhere, or just switch the breaker off.

There's one piece of caution about unpowering a heating unit - if you have a programmable thermostat, it may sip power from the thermo line to keep its backup battery charged; so eventually that could die and you'll have to reprogram the thermostat.

Answer 4

Some have a  fan on switch. It may be just the fan running.