Correlation Between Furnace Blower Speed and Coal Usage?

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Kungur
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Post by Kungur » Thu. Jan. 29, 2009 5:26 pm

I was wondering today if there is a correlation between the speed,or cfm of the furnace blower, and the amount of coal the furnace uses? My thought goes something like this. If I run the blower at a low speed then it takes longer for the thermostat to be satisfied therefore the furnace runs longer.
Comments??
Thanks
Maybe I have too much time on my hands!

 
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WNY
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Post by WNY » Thu. Jan. 29, 2009 5:48 pm

Yes you do! But that makes sense, also, your stove could get really hot if the speed is not high enough to wash the stove off.

 
KLook
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Post by KLook » Thu. Jan. 29, 2009 5:55 pm

I would contend that the slower speed would increase the temp being blown and negate the effect. Some people think moving air feels warmer(higher speed) and some think it feels colder. Set it to how you like it and enjoy! :D I bet some of our heat scientist will have the real answer though.

Kevin

 
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Black_And_Blue
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Post by Black_And_Blue » Thu. Jan. 29, 2009 7:49 pm

I am sure there is a correlation, especially dependent on many variables like the location of the demand thermostat, engineering of the return air system and overall air handler system.

My thermostat is located in a converted garage, this is now my main living room. Three outside walls, 12 foot ceilings, two windows and a door. This is the coolest room in the house and needed the most air exchanged to maintain a steady 70 degrees. I run the circulation fan continuous at 1/3 to 1/2 speed and burn about 60-70 pounds/24 hrs heating 2,000 sq ft of area when outside air temps range 15F-30F.

When outside air temps go below 10F it will require more fan speed to maintain that rooms average temperature and I will burn 10 pounds more coal due to heat loss etc.

To balance the rest of the house, I methodically reduced each vent registers output and measured the changes in each room with a infrared pyrometer.

I am currently revisiting and experimenting with the fan limiter switch settings after reviewing my last electrical bill, seems like the continual blower used a fair bit of power.


 
btrowe1
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Post by btrowe1 » Sat. Jan. 31, 2009 8:55 am

140's and other type stoker stoves, are all about experimenting till you find the correct setup that works for you, I've been doing it for 3 years and I still have ideas :idea: about little changes to try to see if this or that work better. I seem to usually come back to my 1st findings.

Thats the fun :D of coal burning, you can try something and if it doesn't work then you can go back to the way it was and come up with a new idea.

 
pconn171
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Post by pconn171 » Wed. Feb. 04, 2009 4:36 pm

I'm going to have to say that the higher the cfm, the more heat you'll remove from the stove. The air temperature exiting the registers won't necessarily be as hot, but the BTU's will be higher. Temperature does not equal heat. A light bulb is white hot while on, but the thing won't heat a room (unless it's a really really small room). The coefficient of forced convection is proportional to velocity and velocity is proportional to cfm based on the fixed volume of heat exchanger area in the stove/furnace jacket. Having said this, I can tell you that a higher cfm blower will wash away more heat.

 
Kungur
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Post by Kungur » Wed. Feb. 04, 2009 5:33 pm

Thank for that explanation. It makes sense to me. When I install my belt drive blower I will play with the pulley sizes to adjust my cfm.

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