Safe to run circulation fan all night?

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Hello,
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?
Thanks,
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It's suggested to run the fan all the time during the heating season, this eliminates the high and low temps when the system is cycling on and off. Run it. Mark
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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.
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John Gilmer wrote:

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.
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HeyBub wrote:

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.
nate
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Nate Nagel wrote:

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).
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to the AC even if its cool because of its humidiy, but every house is different.
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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 bill.

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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..
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It might be safe but it could also be more expensive.
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I've always wondered how much it would cost to run the fan 24/7... Never did investigate much as I don't have a "Kill-A-Watt" or clamp on ammeter.
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wrote:

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 going on-line.)
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 considerable.
I may think twice before switching the system from AUTO to ON next time.
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When I turn the fan to on the fan runs at the lowest speed. I would need to find the manuals but this may draw a lower wattage.
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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.
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It IS safe, but also costs a bit more since the blower motor runs continuously. For me, it's worth the minimal, added cost.
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Jim Redelfs wrote:

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.
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On Tue, 27 May 2008 15:10:22 -0700, M wrote:

It's harder on a motor to turn it on/off than it is to keep it running. Also starting a motor takes more power. If you find it OK to run during daylight, why wouldn't it be OK to run at night?
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M wrote:

Safe? Sure.
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.
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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.
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In article

Yes.
I will often set the fan to ON - it runs continuously - to accomplish exactly what you describe: Even/balanced heating/cooling throughout the home.
The operation manual that came with my new WeatherKing (Rheem) system, installed 2 years ago, mentions - and allows for - running the fan continuously.
Of course, running the fan continuously will require more frequent filter changes. Good luck.
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