Discharge Air temp vs Blower CFM

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
Nov 15, 2018
21
NWNJ
Looked for similar threads but couldn't find anything so apologize if this was discussed before.
I spend a lot of time tuning my stove this year and adding in ductwork to recirculate air and believe it's close to optimal. The stove is enclosed in a small 8x8 room pulling in air from above living area through ductwork, releasing it at floor level next to the stove. A fan mounted in the ceiling (the floor of the area above) blows s hot air from the ceiling, through the floor joists, under a large kitchen center island which is vented on 4 sides. Kitchen is tile and can get a nice 80+degrees which is amazing for radiation and walking around barefoot.

Question I have is what's the relationship between discharge air temp and how much voltage is applied to the blower motor? I would think there's no need to reduce blower voltage because it only reduces CFM, albeit at a higher temp. To me, running 150 CFM @ 180f out is no better than say 200 CFM @ 170f and I would think the more CFM output the better, even though discharge temp lowers.

I know the "system" is pretty good because I can have a discharge temp of 180f, the living area above at 80f, yet the temp at mid level in the stove room barely gets above 80f while foot level is 70f and ceiling level is 120f. Weird having cold feet and a hot head when walking in there and I assume not much wasted heat heating up the stove room. I always run my blower @ 100%, regardless of feedrate/airflow setting and wondering if there's a benefit of reducing it to get a hotter discharge temp. If not, why is it even adjustable?
 
I always run my blower @ 100%, regardless of feedrate/airflow setting and wondering if there's a benefit of reducing it to get a hotter discharge temp. If not, why is it even adjustable?

The only reason I can see is to make the stove quieter for a particular situation. I've been know to turn the blower down to make it easier to hear a conversation or TV program. I do agree that you'll extract the most BTUs with the distribution blower on the highest level.

YMMV,

Hugh
 
The more airflow the more btu's you are pulling from the stove.
 
  • Like
Reactions: ABMax24
In "in-between" weather, I will turn blower off, so stove still puts out heat, instead of cooking me out, or stopping and starting. Stove is in upstairs, livingroom/kitchen. And, being a Harman, if stove gets too hot, it will turn the blower on, for a bit. It's usually called "fireplace mode".
 
  • Like
Reactions: Washed-Up
You can have the blower off while burning pellets?
I always thought these pellet stoves overheat since they are not made as tough as woodstoves.
Thx for that clarification
 
You can have the blower off while burning pellets?
I always thought these pellet stoves overheat since they are not made as tough as woodstoves.
Thx for that clarification
Not all stoves are built the same, nor have the same features.