Room cooler with blower on high......

[tcassavaugh]

I keep my summit fan all the time as it helps circulate and move the air from the basement to the upstairs, or seems to anyway. upstairs small jotul has no fan but I have a ceiling fan in every room that are always running on low to help circulate the air upstairs

 

[HotCoals]

Its does make sense the secondaries would go out sooner as its how well the temps stay up in the upper part of the stove. Its the temps that make secondaries fire.

Well that's understood.
I still find it hard to believe that a fan would cool the inside of the firebox that much.
But so be it.
I'm just glad that it has no effect on my cat stove that I can see.

 

[thechimneysweep]

Over the years, many visitors to our website have asked some variation of the question: "Why doesn't the manufacturer of my wood stove include a more powerful blower?" So I asked around. Turns out Huntingdog1's point is a valid one. Forced air cools the outer surface of the firebox, increasing the transfer of heat through the shell as described by Hot Coals. Non-catalytic stoves need to maintain around 1100 degrees in the secondary burn area to burn the exhaust from the primary fire and extract the heat. If the airflow from the blower causes too much temperature drop, the secondary burn area can fall below lightoff temperature prematurely, resulting in reduced heat production. I'm told this is why manufacturers limit the blower's maximum airflow, typically to somewhere between 80 and 160 cfm. In some circumstances (say you're burning a relatively low-output wood species on a low draft setting, for example), even the blower selected by the manufacturer might cause the internal temperature to drop below lightoff temp, resulting in the exact complaint voiced by the OP. The operator can compensate by regulating the blower speed to correspond with fire intensity.

Catalytic converters cause the exhaust from the primary fire to ignite and burn at lower temperatures (around 600 degrees) than are needed in non-cats. This might explain HotCoals' observation that blower speed seems to have no negative effect on the heat output of his catalytic stove.

 

[HotCoals]

Over the years, many visitors to our website have asked some variation of the question: "Why doesn't the manufacturer of my wood stove include a more powerful blower?" So I asked around. Turns out Huntingdog1's point is a valid one. Forced air cools the outer surface of the firebox, increasing the transfer of heat through the shell as described by Hot Coals. Non-catalytic stoves need to maintain around 1100 degrees in the secondary burn area to burn the exhaust from the primary fire and extract the heat. If the airflow from the blower causes too much temperature drop, the secondary burn area can fall below lightoff temperature prematurely, resulting in reduced heat production. I'm told this is why manufacturers limit the blower's maximum airflow, typically to somewhere between 80 and 160 cfm. In some circumstances (say you're burning a relatively low-output wood species on a low draft setting, for example), even the blower selected by the manufacturer might cause the internal temperature to drop below lightoff temp, resulting in the exact complaint voiced by the OP. The operator can compensate by regulating the blower speed to correspond with fire intensity.

Catalytic converters cause the exhaust from the primary fire to ignite and burn at lower temperatures (around 600 degrees) than are needed in non-cats. This might explain HotCoals' observation that blower speed seems to have no effect on the heat output of his catalytic stove.

Good read.
The last line is just a little misleading.
I do notice more heat output with the fans on because of heat transfer but the fans don't seem to stall out the converter. Cheers!
I see the edit...thanks for clearing that up.

 

[thechimneysweep]

Thanks HC, I edited the last line so it says what I meant to say.

 

[HotCoals]

Thanks HC, I edited the last line so it says what I meant to say.

While you're here there is a related deal being talked about lately that the fans can cool the flue right at the stove to the point that the draft seems to slow for some...that the fans actually cool the stack.
Have you seen this much?
Do you think that those with the problem if they went to double wall that it would help?
I don't think it's a prob on my stove but not sure.

 

[Lumber-Jack]

I have a different view on blowers and fans.
I have never noticed any significant difference in burn times with my blower going, and I can't see how cooling the metal surface of the top of the stove would have much effect on the fire chamber area that is located below the insulated baffle. That is basically the whole idea of the baffle in modern stoves, to contain the fire in a more confined space to create higher temps and inject oxygen via the re-burn tube for a more complete burn and create extra heat that would otherwise be lost. All of that is suppose to happen in below the baffle, not above the baffle next to the metal surface of the stove.
There is no question that blowing air over the top surface cools the metal surface, but that is not where combustion is suppose to be going on. And there is no doubt that blowing air over the top surface of the stove cools the exhaust gasses, this could lead to more creosote accumulations in the flue (especially with wetter wood), but it would also lead to getting more heat out of the stove and into the house, which, after all, is kind of the goal of heating with wood. If our prime concern was getting the most efficient burn and least amount of creosote formation in our chimneys, stoves would have double insulated walls, no glass, and radiate very little heat. But that is not the goal, we are actually trying to heat our homes, and that means we are actually trying to extract as much heat as is reasonably possible from the combustion before it is lost up the chimney.
If you are not using a blower or fan on your stove to extract heat from the metal surface, then much of that heat simply going up the chimney and leaving your house, this means you are wasting wood fuel and your overall wood burning effiency goes down, not up.

(broken image removed)

Edit; I just thought of a better way to explain it. Think of the combustion chamber below the baffle as the engine in your car, the area between the surface of the stove and above the baffle as the exhaust manifold on the engine, and the chimney as the exhaust pipe. Cooling your exhaust pipe or exhaust manifold on your engine might create more carbon build up in these areas, but it's not going to have any effect or influence on the actual engine performance or running temperatures.

 

[thechimneysweep]

While you're here there is a related deal being talked about lately that the fans can cool the flue right at the stove to the point that the draft seems to slow for some...that the fans actually cool the stack.
Have you seen this much?

We've tinkered with this concept on our test flues with various models over the years, with varying results. By and large, we found a considerable increase in flue gas temps when the secondaries kicked in, and a slight decrease when the blower came on. I should note here that our over-the-counter probe thermometers weren't exactly registering test lab quality results. I should also note that we've never witnessed a wood stove blower, at any speed, cooling the firebox to the point where the secondary flame extinguished.

 

[thechimneysweep]

I can't see how cooling the metal surface of the top of the stove would have much effect on the fire chamber area that is located below the insulated baffle.

Lumber Jack, you seem to be making the point that cooling the outer surface doesn't have much affect on the temperature within. Using your car engine analogy, it doesn't seem to me that we should be looking at the exhaust system as having the same affect on internal temperatures as a blower does on a wood stove. Automobile manufacturers incorporate an air or water cooling system to perform that function. An air-cooled engine might be the best comparison: the airflow promotes extraction of the heat produced inside the cylinders in much the way that the airflow from a wood stove blower promotes the extraction of heat from both the primary and secondary fires. The result is a drop in internal temperatures, however pronounced. Given that wood stove manufacturers limit the maximum flow rate on their blowers, cooling the firebox below lightoff temperature is a rare occurance, but reports we've received over the years indicate that it is possible, so I don't discount the OP's experience.

 

[DougA]

I just have to agree with Lumber Jack on this one. Until the OP actually takes a thermometer and tests his theory, I going with moving air that feels cooler.

The real surface temps of a stove are not going to vary enough to make a difference just by putting a normal blower on. I use a heat powered fan that sits on the stove top and have a digital probe plus an IR gun and there really is no difference. To be fair, I've got a cast iron wood stove and even with the fan on, you really can't feel any difference from 10' away. Personally, I think the fan makes me feel better just by knowing it's supposed to be on. Placebo effect. However, the graphic I found says otherwise. So, in the end, it can't hurt. You will always have some air movement in the room, even if there is no fan. Hot air rises, then falls down as it cools and gets replaced by more hot air. A fan just makes this happen faster.
link to graphic is here: http://realgoods.com/media/catalog/...25d08d6e5fb8d27136e95/1/7/17-0180_-812b-4.jpg

Are there air cooled car engines anymore? In a car, the fan is used to pull air through the rad when you are going slower. At highway speeds, some fans that are electrically driven will turn off as it's not needed.

 

[Lumber-Jack]

Lumber Jack, you seem to be making the point that cooling the outer surface doesn't have much affect on the temperature within. Using your car engine analogy, it doesn't seem to me that we should be looking at the exhaust system as having the same affect on internal temperatures as a blower does on a wood stove. Automobile manufacturers incorporate an air or water cooling system to perform that function. An air-cooled engine might be the best comparison: the airflow promotes extraction of the heat produced inside the cylinders in much the way that the airflow from a wood stove blower promotes the extraction of heat from both the primary and secondary fires. The result is a drop in internal temperatures, however pronounced. Given that wood stove manufacturers limit the maximum flow rate on their blowers, cooling the firebox below lightoff temperature is a rare occurance, but reports we've received over the years indicate that it is possible, so I don't discount the OP's experience.

It's true that automobile analogy isn't exactly the same, because engines have a separate cooling system, but that is because they are deliberately trying to cool the moving parts in and around the combustion chambers, mainly to keep lubricant and metal parts temperatures within designed working parameters. However, my point is still valid, in that cooling the exhaust pipe or exhaust manifold will never have any significant effect on the combustion temperatures or performance of the engine itself, and the same goes for wood stoves, as you seem to have attested to in your previous post. In wood stove we aren't worrying about lubrication and moving parts, and for the most part we are just trying to maintain higher combustion temperatures within the actual combustion chamber.
But the biggest point I was trying to make is that running a fan will cool the top metal stove surface and cool the exhaust gas, that goes without saying. But that heat is being transferred into the house, and that is the ultimate goal is it not? If we are not transferring that heat into the house then where is it going? Up the chimney right?
If we are losing heat up the chimney then we are ultimately not getting as much heat out of the stove as we could be, and that means lower overall efficiency and wasted wood fuel.
When it comes to actual cooling of the combustion chamber, we cool the combustion chamber in wood stoves significantly more by having a glass door then we do by running a blower. If our prime concern was to keep combustion temperatures up we would be far better off having a insulated metal door (no glass), but we go with the glass door and the cooler combustion because, first of all, we want the extra heat to be radiated out into the house, and second, we like looking at the fire.

 

[HotCoals]

I should also note that we've never witnessed a wood stove blower, at any speed, cooling the firebox to the point where the secondary flame extinguished.

I find it hard to believe that it would happen also..yet at least one person on here says it does..I dunno.

 

[Lumber-Jack]

I keep my blower off. Reason being is shown in the pic on the right. I get the heat upstairs in my house better with the blower off. I figured this out 3 years ago then I saw these pics recently that showed me I wasnt crazy. LOL


First pic is with fan on and second pic is with fan off..



(broken image removed)(broken image removed)

What these picture are showing me is that the first picture with the blower seems to be doing a lot better job of heating the room than the second picture with no blower.

 

[Huntindog1]

What these picture are showing me is that the first picture with the blower seems to be doing a lot better job of heating the room than the second picture with no blower.

Your correct, I am heating the upstairs better with the pic on the right.

 

[Lumber-Jack]

Your correct, I am heating the upstairs better with the pic on the right.

Where is the picture of the upstairs???

 

[Huntindog1]

Here is the pic of down stairs

 

[Kosmik]

Well that's understood.
I still find it hard to believe that a fan would cool the inside of the firebox that much.
But so be it.
I'm just glad that it has no effect on my cat stove that I can see.

Wondering if have effect on cooling the secondary air inlet, not perhaps the firebox. Since there is not firebrick in the secondary, it seems that preheating channel would cool off sooner... Exposed to the back.
When the secondaries are running, it seems that on full no problems, but when I choke down, just feels like the stove wants the fan a little lower. I know there is the heat shield before the blower, but when it's pulling all that air?
But part of that may be not always getting a good ditch through the coals to the back of the firebox. (seems to be the biggest reason for me to modify the broken shovel that serves as the all-in-one tool {making anyone nostalgic})
Probably be all fixed up and on high when I get my thermo's in. Probably just running it a little too low, being conservative.

I think they should be focusing on user-friendlyness for mass adoption, instead of lower emissions. Everyone who is on this site, would be in the 'early adopter' category (to some extent)...Showing motivation to seek out the information and make informed decisions...
Most of America isn't like that.
Same reason full dampers on stoves don't kill N.Europeans nearly as much as they would Americans.

 

[madison]

Here is the pic of down stairsView attachment 125463

Where's the psychedelic posters?

 

[madison]

Oh, that picture was not an actual image , haha

 

[Lumber-Jack]

Here is the pic of down stairsView attachment 125463

Is that an un-insulated basement?

 

[BurningBrutus]

So after reading all of these post I decided to do a real world test. Currently i have been running my fan on HIGH to HIGHEST on my Pacific energy Super Insert for the last 3 months. I personally figured running on high would make my house hotter. I decided to see if running on MED to LOW would make my room hotter. Well guess what, i was WRONG. Running on med to low has increased my room temperature by 4 to 5 degrees. I wish i would have tried this months ago! I am actually amazed, i guess running on high cools the air more than i thought. So there you have it, turn your blowers down. Thanks for starting this post.

 

[BrotherBart]

You have been pulling cold air from every corner of the house, and some from outside the house, toward the stove room.

Our couch used to sit between the kitchen and the old insert.. The cold draft coming up over the top of the couch to get to the stove when the blower was on high would give ya frostbite on the back of your neck.,

 

[HotCoals]

i guess running on high cools the air more than i thought

The fans can't cool the air but maybe they can cool the stove to the point the secondary's are effected. That's whats being discussed .
I don't think one cycle or one day can be conclusive due to outside temps and wind and whatever else.
But for you if it works that is great! Cheers!
BB just made a great point also.

 

[Lumber-Jack]

Wondering if have effect on cooling the secondary air inlet, not perhaps the firebox.

I think what you are trying to say is that the blower might cool the secondary air so much that it retards the secondary flames. If so I believe that makes more sense than any cooling of the top of the stove (exhaust manifold) would have.
I actually ditched my blower in favor of a little wall fan that blows down on an angle over top the stove. The wall fan moves more volume of air than the the blower did and heats up the room much faster (assuming the stove is sufficiently hot), but it doesn't blow past the secondary air inlets at the back of the stove. It just removes the heat from the top surface of the stove and a little on the bottom part of the flue. Even so, I've never had a problem with diminished secondaries when I use to run the blower.

 

[BurningBrutus]

The fans can't cool the air but maybe they can cool the stove to the point the secondary's are effected. That's whats being discussed .
I don't think one cycle or one day can be conclusive due to outside temps and wind and whatever else.
But for you if it works that is great! Cheers!
BB just made a great point also.

You could be right, but a few points. Its been consistently cold here, extremely cold for the last 2 weeks, so i have a base line i feel. I have never reached the temps that i have for the last 2 days now, and im using that exact same wood. Another thing i am noticing is my hot peak temp is staying put for at least 1 extra hour during my burns. I wish someone else would try this and see there results.