Extra heat from blower use?

It's my first season heating with coal. I'm heating about 1200 sf of a drafty old house with a Harman Mark I. After several hours of the stove operating at a steady and stable burn, if I turn on the stove blower, the room where the stove is will warm by several degrees within about half an hour. The top of the stove, under which the blower blows, feels much cooler when I put my hand near it. So it seems like the blower is extracting a lot of heat from the stove, which otherwise would just go up the chimney. What puzzles me is, the stack temperature changes very little when the blower runs compared to blower off. I would expect to see stack temperature drop significantly if the blower is really reclaiming what would otherwise be wasted heat. Also the room cools down fairly fast when I turn off the blower. Does the blower really extract extra heat from the stove, or does it just move the heat around differently?

The stove will radiate a given amount of heat fairly consistantly. What is changing is the air temp around the stove because with the blower the air moves faster. By doing so it mixes much more room temp air with the same given heat off the stove. The surface temp of the stove probably changes very little too in this deal.

The slower moving air will pick up more BTUs than the faster moving air. Just put your hand on the stove with and without the blower. See, not much difference.

Thanks, coaledsweat. My neighbor's kid said he would eat a flat dried frog off the road if I would give him five dollars. Maybe I can get HIM to put his hand on the stove for the test.

Seriously, though, I THINK what you said is that the stove will give off the same total heat either way, with the blower on or with it off. Yes?

Correct. You simply change the effect, not the output with the blower.

If I can jump in here..This is my first year using a blower on my Harman TLC2000 (a jacketed stove) & what a heating difference I have seen! I think what is happening here is that, while the stove may be putting out a consistant amount of heat (regardless of a blower) a blower allows you to utilize that heat much more efficiently.
Example:
My home's central furnace is a forced warm air (by natural gas) unit. I would venture to say that when the gas burners are on the furnace puts out the same amount of heat regardless of the furnace blower fan. Without the blower fan on ( sending heat through the ducts) however, it would be pretty useless in terms of heating the house.(the heat would merely pool above/near the furnace & not distribute itself through the house)
Similarly, a blower on your coal stove distributes the heat much more efficiently & that is what we are all trying to do....Heat the house.

It would seem that lowering the surface temp of the stove, by drawing the heat away with a fan, would cause the cooler steel to suck up more heat from the fire. I would think this would reduce the amount of heat going up the chimney. And transfer more heat into the room.

Yes, xackley and Devil..., that's kind of what I thought. There's radiation of heat, and there's conduction of heat. Seems like the forced air blowing over the steel would carry off heat by conduction. And I'm sure that is happening. But because the stack temperature does not go down much when the fan runs, the available heat must be radiated if it is not conducted, so I have to conclude the net effect of the fan is minimal. But it still feels good to stand in that hot fan blast when you come in from the cold.

rberq wrote:Yes, xackley and Devil..., that's kind of what I thought. There's radiation of heat, and there's conduction of heat. Seems like the forced air blowing over the steel would carry off heat by conduction. And I'm sure that is happening. But because the stack temperature does not go down much when the fan runs, the available heat must be radiated if it is not conducted, so I have to conclude the net effect of the fan is minimal. But it still feels good to stand in that hot fan blast when you come in from the cold.

I think what we are all saying is that while the blower fan's effect on the heat being created (& lost up the chimney) inside the stove is minimal, its effect on the amount of heat being transfered from the stove to the room is actually quite critical. The "Heat lost up the chimney" is actualy not changed much but the heat lost (to the room) by mere radiation (lacking the fan's ability to conduct the heat to where it's needed) is significant.
I think the only device actually designed to reclaim some of the heat being lost up the chimney is one of those heat reclaimers (forget the actual name) that connect to the outgoing stove pipe just above the stove b4 it goes into the chimney. As I understand it (having never tried one of these devices) there are clogging up issues with them as well as their draft effect due to the lowering of exhaust gas temps.

I have to preface this post with I know I am a girlie man and have no business in the manly man thread... but I do have something to add to the discussion.

The Magic Heat type air to air heat exchanger works great for coal stoves. It has an ash remover that slides in and out and keeps the heat tubes clean. If you wait for a day with extra draft when the baro is open you can hold it shut and slide the cleaner back and forth and see the fly ash go right out the chimney!

I have a Magic Heat on each of my coal stoves and after over a year of operation have not had any issues with loss in effiency. I run the units continuously (rather than with the internal snap disc rated at 140*F) and control the speed with a rheostat. I find that on average running the unit at full blast reduces the flue gas temp (measured inside the flue directly in the path of the flue gas) by around 15% on average. Although the reduction appears to be non-linear and I have not really checked it at all flue temps.

Hi Matt:
We never said "manly" men were smart, we're just "manly"!
Your comments are always welcome, and helpful.
John C.

Well I guess as we all learn together there may be less distinction.

Girlie man = Democrat, correct? Lemme at the Governator, I show him who's a girlie man.

Ok I will Just add one thing to the term Manly-man It really started out as Real-man vs. Girlie-man somewhere along the
way it was changed I would suspect it was one of the Girlie - Man That might have change it So lets please use the correct Term Real-man in the future when talking to Real-man Hand - Fed Stove Operators Thank you and have a nice night

I too would like to add comment. Correct me if I'm wrong. it's been a while since I looked. On the Harman Mk-1 ,11 , & 111 , the circulator fan blows heat up through channels on the back , and across the top of the stove , but not around the smoke outlet. So , you would be correct when saying the fan takes heat off the steel , and more heat goes to the cooler steel. That would be why the stack temp changes very little. On my HITZER stoves , the air channel does go around the smoke outlet , pulling heat from the stack also. My uncles Harman MK-111 runs a lot hotter stack temp than my HITZER 50-93. And I can feel the difference standing in front of the two stoves. The HITZER throws more heat with a lower fire. We go through the same amount of coal each winter , while I'm heating more than twice the square footage. That being said , My uncle really likes his Harman.

so if it is "real men" I guess the correct term is "fake man" not girlie man.

Doesn't sound quite as bad as girlie... so fake man it is!