making blower fan run 24/7 but on slow speed

ddjjrr

I have an american standard (trane) freedom 95 single stage- model AUH1B080A9421AA. I am getting an air purification system put in and it will work better of course if the furnace fan runs all the time. From what I understand this model of furnace has a 4 speed blower motor. Currently with the thermostat I can have the fan run all the time but it is on the same speed as when the heat is on and I would like to know if it is possible to have the motor run 24/7 on low and when it needs to kick in for heating then run on high or med high as it is now? Is it a matter of getting a better thermostat? Is it even possible?

Jamie Hall

I don't have access to the wiring diagram for that blower -- hopefully someone else here does. However, yes it should be possible to do that, and you shouldn't need a different thermostat. However, depending on exactly how that blower is wired you may need at least one extra relay...

Paul S_3

I believe the homeywell visionpro 8000 can do that....or you can do it with simple 24v coil relays....is this a standard 4 speed psc motor? Or ecm variable

ddjjrr

Thanks Jamie.

ddjjrr

Thanks Paul, the motor is a standard 4 speed motor, not ecm.

SWEI

http://www.icmcontrols.com/FAN-BLOWER-CONTROLS-Prodlist.html may be helpful

John Mills_5

Has to be done in the furnace. Heat is normally medium low, not much difference between medium low and low, hardly worth the effort to rig up relays. If you were to get a ECM upgrade kit, they would have a 1/2 speed constant fan, plus the heat & cool speed and save you quite a bit of juice over running a PSC motor 24/7.

ddjjrr

Thanks John, Do you know if there is such a thing as a ECM upgrade kit for this furnace? I was wondering about that but the furnace is only 5 years old so I guess it would depend on how much it costs. Is it just a blower upgrade or does the control module have to be upgraded also?

John Mills_5

There are several manufacturers that make these. Genteq's Evergreen EM is probably the biggest seller. Just get the HP you need. It has 5 speeds, you choose speed by sending 24v to the 5 taps. You wouldn't have to change the furnace control, just the motor itself. Easy for a technician to do, a very handy HO probably could do it. Looks like low is 1/2 of the highest speed for a better constant fan and use very little juice.

MARS makes the Azure motor that's like it. It wires similarly and works the same with 1/2 speed constant fan. It has a replaceable surge protector standard which is great since most ECM failures are electrical that blow sacrificial thermistors.

ddjjrr

Thanks John, I appreciate your help. I have seen some information on the evergreen motors and they look pretty slick.
I will check out the Azure motor also.
I am waiting for a quote from a furnace company and I will decide what to do then.