Blower speeds and heat output

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Old 12-22-10, 05:37 AM
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Blower speeds and heat output

We have a woodfurnace with a 4 speed direct drive blower. Normally we would have the blower set at high around 1400 cfms, but the air would be cooler. Lower fan speeds will increase the heat output at the register. What is more efficient and effective? A higher blower speed with cooler register temps or a lower blower speed with higher temps?
 
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Old 12-23-10, 10:56 AM
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Anyone have any ideas? I can't find anything about it online.
 
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Old 12-23-10, 11:11 AM
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blower speed

I'm no pro, but I would think that higher speed and lower temperature would not be very comfortable. I think a lower speed and higher temp would not feel so drafty. I do know that you have to be careful not to exceed the temperature rise specified for your unit. Too low fan speed increases temp rise.
Steve
 
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Old 12-23-10, 03:13 PM
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Sdodder is absolutely correct. Other downsides to a high blower speed are increased electrical usage & increased noise.
 
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Old 12-23-10, 04:51 PM
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I'll throw out one more thing. We have 10' ceilings both downstairs and upstairs. Having a lower blower speed, will the heat circulate properly? Its a 1400 CFM blower with 4 speeds, Low, Med-Low, Med-high and High. We had it on high, and moved it to med-high. Then recently I moved it to Med-low and had warmer heat from the registers. We have been able to produce 105* heat from the registers, but wasn't sure about lower speeds. If the high setting is 1400 and ideas of the other settings?
 
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Old 12-24-10, 12:53 PM
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Only 105º? What is the source of heat?
 
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Old 12-24-10, 04:54 PM
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Its a wood furnace. If I lower the blower more, I would get higher temps. The temperature on the limit control shows 150-175 but thats within inches of the heat exchanger. It's rated for an overage output of around 70,000 btus, and a max of 104,000. The air temps can go as low as 85 before the blower shuts off.
 
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Old 12-24-10, 07:41 PM
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Any chance that you have stack tempture gauge on it ?? if reading low then expect the whole thing will be at lower tempture on air.

What kind of wood ya burning ?? if very soft woods I will not go that route get hard woods types they are hotter and they will last much longer per load.

And watch the stack tempture gauge to make sure you are not underfireing { this will cause alot of soot in chimeny }

You may need a speed slector switch one at med low and one at med high depending on the way the tempture rise on the stack and furnace itself.

If you going to run on low fire mode then hit the speed slector on med low that will give you most useable of heat there.

Merci.
Marc
 
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Old 12-25-10, 05:47 PM
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Its a EPA certified wood furnace. The fire temperatures are at least 1200 degrees to promote full combustion, probably higher. We maintain secondary combustion till the coaling stage. My stack temps are around 300 at the furnace, so its extracting alot of heat. We burn all hardwoods thats seasoned. Even on cottonwood we can go overnight in the fall or spring when the temps are in the mid 30's to 40's. I want a speed selector, but I'm not sure what type of switch I need, if you know send me a link. Thanks and Merry Christmas.
 
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Old 12-25-10, 06:08 PM
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I suggest you visit a local electric supply house & I don't mean a big box store. Tell them what you want to do & have things like voltage & amp draw handy. It shouldn't be hard but will require some re-wiring of the furnace which will likely void its safety certification.
 
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Old 12-26-10, 11:22 AM
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Ok thanks. The manual states that you can choose any speed needed. The problem is removing the rear panel to access the distribution block. Having a switch will make things alot easier.
 
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