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
relief.

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
per year.

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".

Good luck,
Gideon

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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?

Thanks...