Fan on/Off

Stack temp on my 50-93 was about 175* today. Power went out for almost two hours. Stack temp never went up. Power has been back on for about 2 hours, stack temp never went down. So much for the theory of 50-93 loosing lots of heat up the chimney when the fan is off. Before today, I never paid close attention. Ya know, heat does naturally rise up the back channel, and out the front. The fan simply helps it along.

I have been watching my 30-95 flue temps closely with the fan on and off. I don't like the noise of the fan and will leave it off under conditions where I am not wasting heat.

With a low to medium hot fire and no to low wind conditions, I see little to no flue temp rise with the fan off.

With a hot fire like 350*+, and/or winds above about 15mph I do see a flue temperature rise when I turn the fan off. I am using a baro. damper but stll see the affect of wind. Above 20mph wind the WC on the manometer will raise above the set of .04 inches.

Quite frankly if I had it to do over, I would buy the model without fan. That model doesn't have the double wall top and back construction. Therefore heat will radiate more efficiently from the non-fan stove than it will from the fan model stove with the fan off.

One can always place a box fan behind any stove to wash more heat off the stove and circulate it if needed. A large box fan will move a lot of air at the low setting, much more quietly than the fan set at any speed that comes on the Hitzer 30-95.

I am confused. Why would you expect to see a rise in the stack temps if you have a barro on your stove? Am I missing something? Doesn't the barro, which doesn't need electricity, control the draft which controls the airflow and determines the temps on the stove? Why would a distribution fan change anything except maybe the temperature in the farthest corner of the room? Just asking because I lost power too yesterday. In fact I often run my stove without the distribution fan on and it never occurred to me that not having it on would increase the heat exiting via the pipe. That's what the barro is supposed to stop. I certainly haven't noticed any difference with or without the fan. Of course I'm running a Harman but it sounds like it has the same basic set up that Oliver described. Lisa

lowfog01 wrote:I am confused. Why would you expect to see a rise in the stack temps if you have a barro on your stove? Am I missing something?

When the blower quits that blows air around the stove, it stops drawing heat out of the stove body and into the room. That will increase the stack temp as it isn't losing as much to the room as with the circulation blower running.

coaledsweat wrote:

lowfog01 wrote:I am confused. Why would you expect to see a rise in the stack temps if you have a barro on your stove? Am I missing something?

When the blower quits that blows air around the stove, it stops drawing heat out of the stove body and into the room. That will increase the stack temp as it isn't losing as much to the room as with the circulation blower running.

To add to what coaledsweat said, On a HITZER, the air channel goes around the smoke outlet. In theory, it should wash heat from exhaust before it goes up the chimney. I don't have a baro damper on my stoves, and seen no temperature change with fan on, or off.

Ok, I see the rational now. Thanks for filling me in. I'm filing all this information away for the next time I buy a stove. Lisa

lowfog01 wrote:Ok, I see the rational now. Thanks for filling me in. I'm filing all this information away for the next time I buy a stove. Lisa

Yes Lisa, I can tell you've been filing away information by reading some of your replies to other posts. You've been paying attention.

I can't disprove your theory, as I don't have a stove with your exact exchanger design.
One thing that contradicts it though, is the testimony of many form members who say that the stove puts out considerable more heat with the blower on than off.

Pete69 wrote:I can't disprove your theory, as I don't have a stove with your exact exchanger design.
One thing that contradicts it though, is the testimony of many form members who say that the stove puts out considerable more heat with the blower on than off.

Yes Pete69, with the fan on, the stoves does put out much more heat. Here's what else I notice; With the fan on, heat is taken off the stove faster, which also opens the bimetal operated draft much more often, producing more heat. What I was saying is that my stack temp didn't change at all between when the power went out for almost two hours(no fan), and two hours after it came back on. I always assumed the fan took heat off the exhaust stack due to what others have said, along with the back air channel going around the exhaust pipe. In theory, it makes total sense. In reallity, not enough heat is taken off to change my thermometer at all. I'm talking about the 50-93 stove. With the 30-95, Grizz does see a difference in stack temps while running at higher temps. I always figured the 30-95 was a little less efficient. They each take about the same amount of coal at tending time.

To say that the stove is as efficient with the fan off as it is with the fan on, all other things must be equal. But if the combustion rate must go down, by the bimetallic damper not opening as often, for the stack temp to stay the same, that is not a fair comparison.

Pete69 wrote:To say that the stove is as efficient with the fan off as it is with the fan on, all other things must be equal. But if the combustion rate must go down, by the bimetallic damper not opening as often, for the stack temp to stay the same, that is not a fair comparison.

Pete69, you're thinking too hard. We are talking coal stoves, not rocket science. I mentioned how my stack temp didn't change the reading on my thermometer. That goes for fan on or off. That also goes for back air vent open or closed. I am saying that if the fan is on, the bimetal air draft does open and close more often. That's because the fan is blowing accross the finns in the heat exchanger, taking heat off the mass of the stove body quicker. Heat from the mass of the stove is what operates the bi-metal spring, which opens the back draft on a HITZER. Still, it did not change my thermometer, which is on the stove pipe. HITZER, being the well engineered stove it is, also has manually operated air vents in the ash pan door. If set to operate harmoniously with the back vent, the combustion air is never completely shut off from the fire.

Nobody has ever accused me of being overcritical before

Pete69 wrote:Nobody has ever accused me of being overcritical before

Yes, fun site isn't it? Keep up the good work pete69.