Hi Ho: We have a Bryant 90 plus (350MAV) to which we recently added an electrostatic filter. Everything works well, but I don't know if the 4-speed motor has a really slow speed which I can leave running. I have the red wire (I think is low speed) plugged in so that turning the blower from auto to on runs on this wire. The problem is that there is very little difference between normal heating (about 8.5 amps) and the on position (about 7.2 amps). Is this really the lowest speed? Is there a simple way to get the motor to run slower i.e. use less power?

Thanks, Dirk

Check the diagram to be sure, but I think you will find the motor speed selections, from highest to lowest, are black, yellow, blue, and red. The "cool" terminal on the circuit board is only powered with a thermostat input to "G" and "Y" at the same time. The "heat" terminal is powered during heating cycles, or when only "G" is powered (with thermostat fan selector switch set to "on"). If using the low (red) motor speed for heating, check the temperature rise of the furnace to assure airflow is sufficient. Values are given on the unit rating label.

The red is usually the lowest speed. Check the wiring diagram on the back of the blower door.

There is no cheap way to get a blower motor to run slower without causing damage. There is a way but the units cost 400.00 to 500.00. They make the motors variable speed with auto ramp up control.

Hi Ho: Thanks guys for the replys. Kind of what I expected, but I am still amazed that a 4-speed motor has so little difference between speeds. I assume the variable speed with ramp-up is like what the Trane system uses. Is there an after-market variable speed system that would work with the Bryant 90 plus?

Thanks again, Dirk

Yes there is a variable speed product but it is not sold to retail customers that I am aware of.

Hi Ho: Thanks again for the quick response. Is that a Bryant system that you have in mind, and if so, what do they call it? I would assume that the controller would also have to be changed? I'm not concerned with having access if I know that it will do the job.

Dirk

It is a after market setup.

FanHandler.com

If you have to worry about the blower speed for your filtering system to work right, you bought the wrong filter system. They make a cartridge filter with a very high merv rating and works better than the electrostatic filter at any speed.

Hi Ho: Many thanks HVAC1000. Just what I needed. The reason for reducing blower speed is not that the system won't work at high speed. It is just noisy, drafty and uses more energy than needed.

Thanks again, Dirk