which speed to run furnace on

[jay2000]

Hello, I would like to know if it's better to run my furnace on low or medium fan speed? I'm not sure if the fan speeds has any bearing on the comfort or efficiency of the system. Any advice would be deeply appreciated.

[Hube]

In the heating season, running the fan on low will certainly be more efficient. When the systems burner and fan finally shut off on a cycle, unless there is air movement, this build-up of heat just "lies" in the unit and goes nowhere. IF you have a "low" speed fan that kicks in when the regular heating speed fan shuts down, it will circulate this semi warm air thru the ducts,etc and do some good. Normally your system should have 3 speeds. LOW, MED or Regular heatspeed, and a HIGH or Cooling speed . To provide good circulation, and efficiency,a lot of air system fans always run on low when the heat cycle is complete. Hube

[jay2000]

Hi Hube and thanks for the info. I guess I'll set the blower to low and see how it performs. It was set at the factory on med. In reading your post, I'm assuming you are referring to the low speed fan that kicks in when the heating cycle is over. My system doesn't have that feature and the only time the fan runs is doing the heating cycle. Could you briefly explain why low speed is more efficient than med speed on a standard furnace blower setup? One other thing is that the system cycles every 10 minutes (10 on 10 off). Is this normal? It seems excessive to me. Thanks ahead for any post.

[Hube]

The furnace's Heating speed is the most efficient when in the HEAT cycle, but once THIS CYCLE IS FINISHED, UNLESS you have a "LOW speed to kick in, the blower will stop running. Thus wasting fuel because there is still heat in the unit that just lies there. IF you ONLY have 1 speed to this furnace now ,LEAVE IT ON THIS PRE_SET SPEED .If you have TOO SLOW a speed when in the HEAT cycle, your furnace will kick out on the HIGH limit.... The motor on these blowers are SPECIAL in order to obtain these various speeds. It seems your motor is NOT equipped to do this. Get a TECH to change to a VARIABLE SPEED motor. As to the short cycling, it depends on the type of system ,thermostat,outside temperature, house layout,etc. With no info one could not advise from here. Good luck,Hube

[jay2000]

Thanks for the advice Hube. I agree, at this point it's a good idea to have a tech come in and evaluate the systems performance and possibly replace the motor. I'll post the progress. Jerry