Should the furnace blower motor fan be set to auto or on? Which is best for the home? For the motor?

Very Controversial question. Some say yes, some say no. Here is my take on it. If you have a newer furnace which has an ECM blower motor, keep the air on all the time. ECM motors run on a lower voltage and are variable speed so they use much less power than a direct drive AC blower motor. If you have an older furnace, use the Auto cycle or your electric bill will shock you.

Just a follow up to my previous comment to therinnaiguy.

ECM motors are only efficient to operate at low torque, this means low speed and static pressure. In other words since an ECM motor is a constant airflow motor, if it is supposed to be moving 2000 cfm, and the filter or ductwork is too restrictive, the motor will get up around to 700 or 800 watts, same as a capacitor run motor.

There are a lot of new thermostats that will alow you to program the blower to run more often, thus increasing air quality when using high efficiency air cleaners/purifiers, and balancing the temperature inside the house without such a drastic change in power consumption.

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Originally Posted by therinnaiguy

Very Controversial question. Some say yes, some say no. Here is my take on it. If you have a newer furnace which has an ECM blower motor, keep the air on all the time. ECM motors run on a lower voltage and are variable speed so they use much less power than a direct drive AC blower motor. If you have an older furnace, use the Auto cycle or your electric bill will shock you.

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Please forgive my ignorance, but what does ECM stand for? The furnace is practically new (3 yrs. Old) and the blower motor recently quit running. Had to have it replaced, but I do seem to recall the repairman when he was diagnosing the problem say at first that it might be the capacitor and not the motor.

Well, an ECM motor ( electrically commutating motor ) does not have a capacitor, so that may answer the question.

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Originally Posted by NorthernHeat

Well, an ECM motor ( electrically commutating motor ) does not have a capacitor, so that may answer the question.

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So to answer my original question, having the blower motor constantly ON rather than Auto will give me better air circulation and heat distribution but will cost me more in electricity, right? Having the motor set to ON is better but more expensive, I'll get what I pay for . Is that correct? Thanks for your help.

Only about a few dollars more per year and is worth the cost to keep on.

A few dollars more per week.

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Originally Posted by NorthernHeat

A few dollars more per week.

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NorthernHeat,
You are the heating expert, what is your blower set on? AUTO or ON? If on, are the benefits worth the extra $. Will it affect the longevity of the motor? Pros ~ Cons?

My ductwork is in a cold attic so I don't runn it in the winter, but I do at times in the summer. Flex ductwork doesn't have the best R factor so I don't wish to hurt my fuel efficiency by picking up any extra cold air. I strongly suggest if you run a blower continuous you have a high efficiency air filter in place. Also beware of pleated fiters, they are good at trapping dirt but are restrictive on airflow and doesn't take much dirt to plug them up. It is my opinion, but I wouldn't live without an Aprilaire Space guard filter. Of course when installed everything must be tight and sealed, including inside the blower compartment. To often I see these units poorly installed and dirt is pulled into the evaporator coil and blower wheel through the door, bottom and penetration holes of the furnace.

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Originally Posted by Tim M

Should the furnace blower motor fan be set to auto or on? Which is best for the home? For the motor?

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AUTO all the time in the cold season, ON to check it out , check power supply, and maybe summertime cooling if you have a cool basement.