How does this home HVAC system work??

[McLovin]

Can’t figure this out, my Google is weak on this one.

It’s an older system, maybe 15 years or so?

I believe it’s a single system, split between the upstairs and the downstairs (so each can be controlled separately).

Here’s the controls. Pictures are upstairs control, downstairs, and a third box mounted in a closet.

[McLovin]

The issue I’m having is sometimes the blower fan randomly goes on. It’ll run for a while, then shut off. There’s no heat or ac when it does that, just the fan.

There’s no pattern that I can tell.

It seem like the way I have the levers set, the system should be “off” and not do anything.

I even shut off the breaker labeled “A/C” and the blower still does its random thing.

Can’t figure out if I’m doing something wrong, or there’s something broken/wrong in the system.

[notmytarga]

The thermostat box is more than 15 years old. My family home had one 40 yrs ago. The closet box may be a newer communicator - I would think the T-stats would be out of the loop.
My Honeywell wi-fi T-stats do turn on the blower for 'recirculation' 35% of the time and at a lower blower speed - uses little relative enrgy and balances out the room temperatures. Fan settings are Auto - ON - and Circ etc.

The AV breaker will only cut out your outdoor AC condenser unit. The furnace fan is powered by 120V and located separately.

I am glad to answer early - none of what I said is wrong but won't be an helpful as others!

[billybek]

It looks like the Trolatemp Total Zone is a sharing system and should have a damper to direct air to two different zones.
I found the manual online and will try to find it through the honeywell site when I get to work.
Those Chronotherm stats were available when I was doing commercial work over 30 years ago...

[masraum]

Originally Posted by McLovin

The issue I’m having is sometimes the blower fan randomly goes on. It’ll run for a while, then shut off. There’s no heat or ac when it does that, just the fan.

There’s no pattern that I can tell.

Originally Posted by notmytarga

My Honeywell wi-fi T-stats do turn on the blower for 'recirculation' 35% of the time and at a lower blower speed - uses little relative enrgy and balances out the room temperatures.

I'm not familiar with the specific hardware, but my guess is NMT has it. THere are HVAC controls that will tell a system to "move the air around a little bit every once in a while" which is especially useful when there's an upstairs and downstairs (hot air rises). My experience is what NMT says, you can set some systems to circulate the air X% of the time. What that usually means is "even if the HVAC hasn't run, every hour or every 30 mins or every X-time, kick the fan on for . In our old place, that was super useful in the time of year (spring and fall) when we didn't need the AC but without the fan, the upstairs/downstairs temps could end up 5-10º different.