HVAC Question

I have a (to me) weirdness in my heater/air conditioner system. I live in a high-rise building, which is about 3 years old and my apt. has forced air HVAC. Everything seems to work as expected but there’s this one thing….

Every so often, say every 2-4 hours (it’s so “random” I’ve never tried to time it), the fan will fire up. The fan will operate for 10 seconds or so and then shut down. This happens in summer and winter (i.e., it appears to be independent of whether I’m using AC or heat). Since my apartment rarely varies much in temperature (good insulation?) I rarely use the HVAC system which is why I notice this.

Here’s what makes it weird: it happens when the thermostat is turned off. Every domicile I’ve ever occupied only uses the fan when actively heating or cooling (some folks, of course, set the fan to always run, not I). With the thermostat off, there shouldn’t be any activity, right?. If the thermostat is on then of course the fan fires up to heat/cool but how come it comes on sporadically with the thermostat off?

Any HVAC folks have a SWAG? Is it some kind of code issue where the air has to be shoved around to insure it doesn’t get stale? The water heater (a really big mother) is in a utility closet within the apartment so maybe the architect was concerned with CO2?

I installed systems for 5 years, a long time ago.

lemme see…theres on/auto/off and heat/cool…so off would be OFF=nothing running.

A few things it might be.

Energy Management, from power company.
ECU for hot water.
Electrostatic Filter.

All these have some low voltage wiring to the System and could be faulty if just the Blower is running intermittent.

All I can think of is a timer that is bypassing the thermostat. Or, the low voltage wires are getting pinched by something some where.

There is no reason the Fan should Blow when it is clearly the whole system is supposed to be OFF.


Apparently there is a reason. Thanks for the response; I think I have the answer.

Heat for the apt. (as well as for showers, etc.) is supplied by a HUGE (for a studio) water heater. Every so often the fan is triggered, even with the thermostat off, so as to cool some parts of the system. That’s why it’s for a short run only.