# Current of central heat fans

• posted on December 4, 2009, 3:34 am

Can anyone tell me the general draw of a squirrel cage fan in the plenum of a heating/ cooling system in one or both speeds? I'm trying to decide if this fan is cost effective (I'll do the math) for distributing the heat from my wood stove. I have always contended that every use of it defeats the purpose of burning wood. TIA Chuck
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• posted on December 4, 2009, 4:01 am

I get my wood for free this year so I'm using the fan to distribute the heat from my heatolator fireplace in the family room thruout the house.
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• posted on December 4, 2009, 4:14 am

In my 5-ton A/C, 100,000 btu heating system, the blower is about 10 A, mebbe a little more. But this is a big-azz blower, ballpark about 1 foot long by about 1 foot diam squirrel cage.
10 A, at a power factor of 1.0 (purely resistive) is 1200 watts, a good sized heater in itself. Which is something you should consider, that technically, this electric cost is "returned" in the form of heat, altho not "free" heat, as in chopped wood. Of course, this "return" of heat is undesirable in the A/C mode.
I'd guess that the blower suitable for a wood burning stove would be much much smaller. For example, the blowers in kitchen hoods are considerably less than 5 A, some less than 2 A, gleaned from a GE Profile sheet on their designer hoods.
I think a current draw of 2-3 amps would increase the effective heat distribution of a wood stove so as to be well worth the electric cost. Ceiling fans also do well along these lines, and draw very low power.
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EA

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• posted on December 4, 2009, 8:29 am

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You probably have a dual speed fan. Low speed for circulating hot air and high speed for circulating cool air. The current draw is listed on your specific models motor data plate, or you can just use an ammeter.
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Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
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• posted on December 4, 2009, 10:50 am

Look at the nameplate on the motor and it will give the amps for running.
The biggest drawback of a wood stove is the lack of air circulation. To be effective in the entire house, you must move the air somehow. If you don't use the blower from the heating system, run a box fan to blow the heat out of the room to the rest of the house. You can get some natural convection, but in 99% of houses, it is not adequate.
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• posted on December 4, 2009, 12:47 pm
C & E wrote:

Won't running that fan draw some smoke into the house that might otherwise exit via the chimney?
Lou
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• posted on December 4, 2009, 1:09 pm
Yes, very possibly. Some heat systems run a duct (4 inch dryer vent tube would be good) from the return air to outdoors. So, the system pulls in some outdoor air. Helps pressurize the building, too. Push the smoke out.
I remember the one time I was helping install a furnace. The family decided it was a good day to kindle a fire in the fireplace. The house was airtight enought, that the fireplace was sucking air down the chimney (flue) for the furnace. The smoke started to fill the cellar. Really bitter, and miserable smoke, too. I took a plastic bag and taped it over the open flue. And then opened a cellar window to let fresh air in.
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Christopher A. Young
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• posted on December 4, 2009, 4:59 pm

if the stove has a air input from outside the house there is no problem. My fireplace, which is a heatolator type, draws air into the firebox thru a 4 inch diameter hose which goes directly to the outside through a dryer exhaust like pipe and hood and screen on the side of the house. The heat exchanger is a blower that blows air around the outside of the fire box itself. There is no air interchange between the outside air being drawn in for combustion and the air blowing around the fire box.
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• posted on December 5, 2009, 2:24 pm
hr(bob) snipped-for-privacy@att.net wrote:

I see said the blind man to his deaf wife!
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• posted on December 4, 2009, 2:24 pm
Well.... a typical furnace blower is 1/4 to 1/3 HP, some are larger. A HP is 748 watts, or maybe 746. Can't remember.
My prediction is that using the furnace fan helps keep the other rooms much more comfortable. Cuts down on complaining. And helps filter ash and dust out of the air. All of those, are valuable.
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Christopher A. Young
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• posted on December 4, 2009, 4:37 pm
I have a Trane XR 80 furnace for my house. Looks like a standard size furnace. I remember when I borrowed a friends Amprobe, I saw about 5.5 amps for the blower.
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• posted on December 4, 2009, 10:09 pm
Stormin Mormon wrote:

My furnace fan has surprisingly little effect on circulating heat from my insert. Run for a couple hours when the living room is up to 70, the other rooms might rise from 60 to 62. It probably depends a lot on where you cold air returns are. If they are right next to the stove, it'll probably work better.
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• posted on December 5, 2009, 8:44 pm

Just looked at the plate of my old dual blower for kitchen vent, hellified blower. 1/20 hp!! mebbe 1/2 A? wow....
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EA