Our installer told us to run our air blower on manual and continuously. During the winter months, it seems to make the house "drafty" by pushing unheated air through the system when the furnace is not running. He also said that the cost of running the blower would be negligeble. What are the benefits and disadvantages of this situation. Could anyone provide advice. The furnace was installed approx. two years ago. Thanks.

How old is the furnace?

I would leave the furnace blower on auto but not on manual.

The newer furances have a blower that has multi speeds and the blower will run on low speed when the burner is not on. This is supposed to keep cold spots out of the house. If your furnace only has a one speed blower then I would not keep the blower on manual. It will keep cooling down the house and making the furnace run longer.

Thanks for your reply. The furnace is just two years old. I don't know if the fan is multi-speed as you suggest.

If it has a multi speed blower then you will feel a different velocity of air coming from the vents at different times of the heating cyle. If you only feel one velocity of air coming from the vents then you may have a one speed blower. You should have an owners manual that should tell you if the furnace is a one speed or a multi speed blower. See what the owners manual has in it.

Most people leave the fan on auto. Most blowers have a range of speeds the installer selects to make it run the most efficiently. That is nearly always a slower speed for heating than cooling. Usually the furnace is wired to give the higher speed on continuos.

If you find the continuos fan drafty and uncomfortable, try turning it to auto and see how you like it.

I have seen no tests showing which one is better. I have read that running the fan on a windy day reduces air infiltration, but do not know if the guy had any proof. Many opinions have no facts to support them.