I have central air and a gas furnace for heating, and I believe one
system controls the air circulation. When it gets hot out, the a/c
doesn't cool the upstairs well. My thermostat has the option to keep
the circulation fan on all the time, not just when the AC (or heat)
turn on. I believe this will help a great deal, but hubby says it
isn't built for that and we will break something. Is it safe to run
the circulation fan all night, or should I save that for more
conventional house fans?
Believe it or not, the circulation fan (if it's a standard 3-speed) uses a
fair amount of electricity.
When the heat is off but the fan is on you are blowing about unheated air.
I just don't see how that helps anything.
In the summer you definitely don't want to run the fan all the time. When
the compressor cuts off there is still a little water on the coils. If you
keep the fan running, this water is evaporated and inceases the humidity of
the living space.
Summer or winter, the fan does consume some energy.
The blower is, what, 1/4HP? That's about 200 watts. Running for ten extra
hours in a day is 2 kwh. At 15c per, that's thirty cents a day, $9.00 a
month. To keep the temperature relatively constant.
Plus, keeping the temperature constant via continued circulation doesn't
make you think you're going through the hot flashes of menopause. Peace of
mind is worth something.
In my house the basement is consistently cooler than the second floor.
Keeping the fan running makes both more comfortable. Certainly beats
running the A/C cost wise. I left the fan running when I left for work
this AM and it was close to 80 degrees out when I got home. The house
was about 70 degrees inside, had the A/C set for 77 degrees, so
obviously it never kicked on all day. (I must admit that it was cool
last night so the inside temp. was about 66-67 degrees when I left,
because I'd had the windows open and a big window fan running to cool it
off before I went to bed.)
I'm sure that if I *hadn't* had the fan running it would have been at
least 75 upstairs if not higher - I can say this because I didn't have
the central A/C last year and just had a mercury thermostat with no fan
switch, so I didn't have the option of leaving the fan running.
replace "roosters" with "cox" to reply.
Right. You have a basement that acts as a heat sink, storing up coolness
which you can pipe to the rest of the house.
We don't have basements where I live: the city sits on 500 feet of mud
(well, clay - same thing).
You are assuming the motor is fairly efficient. These three speed motors
aren't designed for efficiency. The 1/4 or 1/3 hp rating is what's deliverd
to the fan.
If you have a well balanced system, the most heat is delivered to the rooms
that have the most heat loss.
The air you circulate when the furnace is off will be a room temperature.
All you fan is doing is creating drafts.
I don't see how creating drafts would bring much peace of mind. Folks
with gas heat typically pay less than $100/month for electric in winter.
So your "peace of mind" is adding 9% (using your number) to you electric
I have a ridge vent on a roof that was installed in late 01 along with
the 3 existing gable vents. They all went through 3 hurricanes in 13
months. No problem..
If anything, one of the gable vents had some wind driven rain come in.
Fema solved this with a vent shutter..
About $24/months. (wow) Read on...
One horsepower equals 746 watts.
Of course, according to my engineer/friend, that is given 100% power
factor and other mumbo-jumbo.
Also, a typical blower motor is 1/2-horsepower. In any case, I'll use
that in my calculation as I have always wanted to estimate the CO$T of
running my blower 24/7.
My friend said he was being generous when he claimed my motor might be
delivering at 80% efficiency. I asked him to guesstimate a WATT amount
for my motor: 500. OK. We'll use that.
Now, how much for the electricity?
Omaha Public Power District's highest residential rate is 8.66-cents per
kWh. I *LOVE* my "cheap" power!
(I feel sorry for you poor slobs that are - and always will be - paying
for a brand new nuke that was decommissioned mere days prior to its
OK. 10-cents/kWh is a good rate to use.
How often would a system CYCLE (turn on-then-off) in a 24-hour period?
Just for the sake of our little calculation, let's say the system would
cycle and run for 1/3 of the time.
Using the above figures, the 24/7 blower would cost $1.20/day.
The cycling blower would cost 40-cents/day.
The difference is 80-cents/day time 30 days = $24.
$24 EXTRA per month to run the blower continuously.
Hmmmmmm... That's somewhat more than I had expected. It is
I may think twice before switching the system from AUTO to ON next time.
During hot spells, I always leave the fan on. Last year when I checked
with my amprobe, I think the fan used about 6 amps@110V amps. My CAC
compressor uses 14 amps@220V.
So thats 660W vs 3800W. Big difference. You obviously save more
electricity running the fan more and the CAC less.
Our system has a continuously variable blower and the specs require that the
fan switch on the thermostat be left in the "On" position all the time.
Then the board on the furnace controls everything to do with the fan.
There might be times when it goes completely to off, but most of the time it
is always turning at a low speed.
Break something? If that were a common event, the manufacturers wouldn't
give you the opportunity to do so. Their motors honor the "fan" setting of
the thermostat, don't they?
If you want to save money, equip your bedroom with a ceiling fan.
If you REALLY want to save money, get a window unit for the bedroom. You can
probably get a completely servicable one for less than $200 that will pay
for itself in less than a summer.
It is fine to do that, but another option would be a t-stat that has a
"circ" option for the fan, where it runs the fan around 30% of the
time to even out the temp throughout the house. The Honeywell
VisionPro has the option, and I'm sure others do to.
I will often set the fan to ON - it runs continuously - to accomplish
exactly what you describe: Even/balanced heating/cooling throughout the
The operation manual that came with my new WeatherKing (Rheem) system,
installed 2 years ago, mentions - and allows for - running the fan
Of course, running the fan continuously will require more frequent
filter changes. Good luck.
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