Friday, February 27, 2009

What is "Main Air Circulating Fan"

The new stimulus bill has a tax credit for "main air circulating fan" accourding to Energy Star web site. Well what does that mean. The answers are not clear yet. It looks like congress got ahead of the HVAC industry manufactures. This rebate has not been cleared up yet. But if you look at the original 2009 and 2007 Energy Tax credit that meant if you buy a furnace with a ECM (Electrically communicating motor) blower you got $50. More commonly the ECM motors are known as "variable speed" furnace.

What is benifit to V.S. motors?

The average furnace in your home has a motor that is typically 45-50% efficient. So meaning every dollar you spend to run the furnace fan you waste 1/2 of it. The average VS motor will be 95-98% Efficient. So you only wast 5 cents out of every dollar you spend. A typicall 2000 Sq Foot home in Minnesota running there furnace fan in the "On" position on the thermostat will spend about $200 per year in electricity. If you have a VS furnace that will drop to about $45-60 per year. It is not uncommon to save $150/year. The cost savings will go up to $225-275 per year when you get into a larger home around 3500-4000 Sq Foot.

Why should you run the furnace fan 100% of the time?

  • better air quality because you are always filtering the air as it goes through the furnace filter
  • more even temperatures from room to room in your house or even more even temp from one floor to another

What is down side of running fan 100% of time?

  • cost more money if you don't have an ECM motor
  • worse dehumidification in the summer time when cooling

So now, what does this new tax credit mean for the Stimulus Bill?
No body knows yet. (nice answer, I must be in congress) The way it currently reads accourding to Energy Star if you buy a qualifying furnace with ECM motor you will get a 30% tax credit with a max payout of $1500. That is a great deal if it turns out that way. Currently I have talked with multiple manufactures like Trane, Bryant, Amana, Goodman, and UPG(York) and they are all trying to get clarification from the IRS on this. So far it is looking like a good deal.

Ok, one more catch. There is one know fact but not talked about with having an ECM motor in your furnace. If you have a poorly installed duct system you may not save as much money as you should. Furnace duct systems are rated by Static Pressure. It is like your blood preasure, the higher it is the worse. If you have a poorly installed heating or cooling system this will easly double the design static pressure which will then drastically increase your electrical use. The Static Pressure should be tested regularly on your HVAC system, but unfortinatly only about 10-15% of heating contractors even know how to do it. It is easy, and doesn't cost much. A quality HVAC contractor will test static pressure every time they are servicing your system or installing a new one. There are many ways to save money in energy use, it just takes the right heating and cooling profesional to help you.


  1. Just guessing, but I think a "Main Air Circulating Fan" actually refers to what's called a "Whole House Fan" which is typically installed in the attic to draw stagnant heated air out of the attic and draw cooler air into the house during the summer months.

  2. It is definitely referencing the furnace fan. This is the same term used in the 2006-07 tax credit that paid $50 for variable speed furnaces. Also the EPA web site references GAMA as the regulating company, which they rate gas appliances.

    Attic fans are another subject. Be careful, they can commonly waste a lot of energy.

  3. The IRS is suppose to release there interpretation of the tax credits by the end of March 2009.