For some people, running the blower fan 24/7 is very practical.
I've been doing it for years. In the past 10 years, my blower fan
has been turned off only when I'm working on the system and
have to kill the power. I find that this lowers the operating cost
of my somewhat undersized AC unit. It also maximized air
flow through the furnace filter system, which provides allergy
Furnace blower motors are well designed and intended for a long
service life. The only problem with running one 24/7 is the fact
that you MUST oil them frequently. Once a year is an absolute
minimum. I prefer 3 to 4 times per year. On my furnace, the
entire process of removing the fan assembly, oiling both oil ports,
and reinstalling the fan assembly only takes 5 minutes. I also
oil the fan motor in the AC compressor box a couple of times
By the way, you are asking the question, "does running 24/7
reduce fan motor life?" The more important question is, "does
running 24/7 significantly increase the chance that the motor will
fail before the furnace is replaced?" Generally, the answer to the
second question is "no".
BE wrote in message ...
Just a question regarding the blower motor on my furnace. I just had the
evaporator AC coil replaced. I mentioned to him that even before it went
bad the home does not seem to stay cool for long. He told me to leave the
fan switch on the thermostat to on so that it blows 24/7
Well needless to say that makes a huge difference as the compressor isn't
needed as much.
My concern is will this shorten the life of the motor? And, is it ok to
leave the fan on 24/7 for 2, 3, 4, 5 days? My thinking is to leave it on
for whatever the duration of the heatwave. Correct?
Thats what most of us in the trade do. The motor will normally last much
longer this way.
If you have poor air circulation, you will notice it more since you are
helping to move the air that is called stagnated air around more.
Mines been on 24-7, other than when I am servicing the unit every 6 months,
for the past 4 years, and its not going to be cut off any time in the
The motors that we replace the FEWEST of, are the commercial applications
that the fans run 24-7. We have some that have been on for over 9 years
without a problem.
Depending on your airflow situation, you may even find that with the added
electricity that is being used, that your power bill may drop, due to
reduced compressor run times.
I gotta agree with Stretch about the humidity issue. Whenever a customer
calls about humidity being too high, the first question they are asked
is "Do you have the fan in the on position?" If so, as soon as the
compressor shuts off, the system converts from being an air conditioner
to an evaporative cooler. We have a policy that if we are on a call, and
find the fan in the on position, to let the customer know this, advise
them of the possibility of getting mold in the ducts, then note it on
the invoice and have them sign it. We also find besides air circulation,
some people will run the fan continuosly for the constant noise, which
they get used to, rather than having it on and off-- especially people
with infants sleeping. (Usually these are upflow units in a hall closet
close to the bedrooms) Larry
Now this is an interesting one.
Not flaming you man, but what you say just went against everything in IAQ
that has been taught by better than you and I.
Mold on ducts? Evap cooler?
The water left on the evap coil should be gone in a few minutes AFTER the
condensor shuts down, due to drainage and like you say, evaporation. Water
is not being poured over the coil as in an evap cooler, so you have a min of
water that is being added back to the indoor air.
The water in the pan, well, if the units installed right, there will be none
left after about 10 -15 seconds of off time...provided its trapped, (if need
be) and the unit, (and hence the pan included) is installed correctly.
The fact that the air is being filtered, and not allowing to become stagnant
in some areas would inprove indoor air quality, and not hurt it.
Should you find a home where the pan is full of water, or the coils covered
in mold, then, a good tech would suggest that the lines be cleaned, the unit
be set correctly, and the coils cleaned. The addition of a UV-C band unit
would be a strong suggestion as well.
The water that is being pulled off the coil and being evaporated by the
cooler, dryer air that the unit just treated, would be minimal in a
situation where the unit is sized and operation of the unit is correct. I
doubt seriously that you would even get a 1%RH raise after the blower has
moved enough air over the coil and pan to evaporate the remaining water.
The mere fact that the water is being removed rather quickly from the coil,
removes one thing that mold needs to grow, and remove the water, you remove
one thing that mold needs out of the three to grow. Mold needs water, dark,
and a food source.
Pans that are allowed to sit there with water in them, sure...those units
will grow mold. Units that are oversized, and only cool the air, and not
remove enough water from the air, those will tend to grow mold as the air
left in the ducts and home is laden with excess moisture. Units that have
poor drainage qualities to the pan due to incorrect level or poor drainage
of the condensate they willl grow mold as well.
IAQ is normally, assuming the unit is sized correctly, the ducts are
installed and sized correctly to the unit, and home, improved by running the
If not 24-7, the addition of a Honeywell stat with circ capabilities that
will cycle the fan X number of times per hour is a good addition as well.
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