blower ideas?

Grisu said:

If the engine would be on the passenger seat, it would make only a small difference. Mainly make me warm a little bit faster. The total heat delivered by the engine for a given amount of gas will be the same. A stove is within a shell, not outside like a car engine. If you would not turn on the car blower, the engine will heat the outside air, not the passenger cabin.

It is really not rocket science. Any energy not going up the flue will end up in your home. It does not disappear. A blower will make you feel warmer faster but the total heat delivered over the burn will be the same as long as efficiency is not affected.

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The engine may not be on the passenger seat but the heater core is in the cabin area.

Think of the hot water passing through the heater core. Same idea as the heat from a wood fire passing through to the flue.

I don't understand why some will not concur that the heating efficiency of a wood stove will be higher with fans on.

I hardly ever use my fans because I don't like to hear them. That said when it gets below 10f I do run them at times and they heat my house up to a warmer temp all else being equal compared to them being off.

Why do you think computers have fans..to dissipate heat,plain and simple.

HotCoals said:

The engine may not be on the passenger seat but the heater core is in the cabin area.

Think of the hot water passing through the heater core. Same idea as the heat from a wood fire passing through the flue.

I don't understand why some will not concur that the heating efficiency of a wood stove will be higher with fans on.

I hardly ever use my fans because I don't like to hear them. That said when it gets below 10f I do run them at times and they heat my house up to a warmer temp all else being equal.

Why do you think computers have fans..to dissipate heat,plain and simple.

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I think I read somewhere that fans on a woodstove increase efficiency by 1%in SBI literature. Not even noticeable.

realstihl said:

I think I read somewhere that fans on a woodstove increase efficiency by 1%in SBI literature. Not even noticeable.

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Well I can tell you it's higher then that.

At 10f or below I can raise my house temp at least 5 degrees with the fans on. I'm talking two rooms over and still hold the same temp in the stove room.

If we were to go by what you're saying and or SBI we would have to conclude that fans are just a market tool, profit maker deal and that only fools would buy them.

madison said:

The analogy I was trying to make was for heating the interior of the car, not the exterior engine compartment. So you turn the car's heater blower on to REMOVE engine heat (via the engines cooling system) and warm the interior of the car.

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What are you describing here translates to an outside wood furnace. Of course that needs ducts and a blower to move the heat into the house. Totally different from a woodstove sitting in your living-room though.

Regarding heat lost up the flue, if you remove the heat from the stove exterior more efficiently - i.e. with a blower - less heat would be lost to the chimney.

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Only if the blower affects the combustion efficiency as Owen has already pointed out. Tell me: Would you get more heat out of an electric heater with fan than an electric baseboard when both have the same wattage?

Nonetheless, I do agree with some of your thoughts - just not all of them... No big deal. I'll still continue to use the blower.

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I still use mine, too. I turn it on when the stove is above 600 F and turn it off when the secondaries become weaker again. However, I am under no illusion that the blower will give me more heat. I'll do it to distribute the heat faster and reduce the risk of an overfire. I am also hoping to increase the efficiency a bit but would consider that a bonus. And my insert still heats our home just as well.

Fundamentals of Heat Exchange: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCYQFjAA&url=http://www.aip.org/tip/INPHFA/vol-2/iss-4/p18.pdf&ei=qfZXU8KMNYLNsQSf0oHADQ&usg=AFQjCNEZjE_t8iJuSyd-TYmHgUv43TT3Pg&bvm=bv.65177938,d.cWc

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And where does it say that heat exchange will get you more heat out of any heating system than what is there to begin with?

HotCoals said:

The engine may not be on the passenger seat but the heater core is in the cabin area.

Think of the hot water passing through the heater core. Same idea as the heat from a wood fire passing through to the flue.

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So now we are talking about increasing the efficiency by reducing the amount of heat that goes up the flue?

I don't understand why some will not concur that the heating efficiency of a wood stove will be higher with fans on.

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As I do not understand why someone keeps insisting that blowers on woodstoves negate the first law of thermodynamics. Btw. Morso only supplies blowers with their inserts because the customers want it. As I pointed out earlier, if blowers would make such a difference why does the EPA not demand that stoves only be sold with them?

I hardly ever use my fans because I don't like to hear them. That said when it gets below 10f I do run them at times and they heat my house up to a warmer temp all else being equal compared to them being off.

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Do you then load your stove more often? Plus, with cat stoves that like to run at low and medium temps you may improve the efficiency by cooling them down to get them in their optimal working temp range. Exactly what I had pointed out earlier.

Why do you think computers have fans..to dissipate heat,plain and simple.

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And where would that heat end up if you would not turn on the fan? Disappear in a parallel universe?

Grisu, I think what you're missing is that with the fans on the stoves surface is cooled somewhat. Because of that heat from inside the box can then be transferred faster through the steel of a stove to the surface of the stove instead of going up the flue.

Look at Magic Heat boxes ..they worked so well they cooled the flue pipe to much.

Grisu said:

And where would that heat end up if you would not turn on the fan? Disappear in a parallel universe?

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Well it would not matter because your puter would have died after awhile.

Grisu said:

So now we are talking about increasing the efficiency by reducing the amount of heat that goes up the flue?

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Yep.

BTW..the EPA is only concerned with what comes out the chimney is my thought.

HotCoals said:

Grisu, I think what you're missing is that with the fans on the stoves surface is cooled somewhat. Because of that heat from inside the box can then be transferred faster through the steel of a stove to the surface of the stove instead of going up the flue.

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Yep, and then you cool it too much, your secondary combustion stops working and you lose unburnt gases which are going up the flue. That's exactly what the EPA would not want. Neither would it like you burning more wood and producing more CO2 to get the same amount of heat into your home. I am apparently not alone with my opinion about blowers: http://www.woodheat.org/qa-wood-stoves.html

"I don't use a fan of any kind and I don't promote them. There hasn't been much independent research on the efficiency of fan use, but many years ago I do recall one obscure study that found only a very slight difference in efficiency when the fan was used, and this was on a fireplace insert with small air circulation passages around the entire firebox..."

How many stoves at the Greenheat challenge in DC 6 months ago had blowers? Those stoves were scored on energy efficiency. If you are fighting for the best score in a competition would you not add one of the easiest accessories possible to get an edge? Unless, of course, it would not give you one.

Grisu said:

Yep, and then you cool it too much, your secondary combustion stops working and you lose unburnt gases which are going up the flue. That's exactly what the EPA would not want. Neither would it like you burning more wood and producing more CO2 to get the same amount of heat into your home. I am apparently not alone with my opinion about blowers: http://www.woodheat.org/qa-wood-stoves.html

"I don't use a fan of any kind and I don't promote them. There hasn't been much independent research on the efficiency of fan use, but many years ago I do recall one obscure study that found only a very slight difference in efficiency when the fan was used, and this was on a fireplace insert with small air circulation passages around the entire firebox..."

How many stoves at the Greenheat challenge in DC 6 months ago had blowers? Those stoves were scored on energy efficiency. If you are fighting for the best score in a competition would you not add one of the easiest accessories possible to get an edge? Unless, of course, it would not give you one.

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Well that's his opinion.
As far as the challenge I know nothing about that. Did they even allow blowers?
Look I don't use them much ,only when it's real cold.
But I can tell you in my house they do make a difference.

HotCoals said:

Well I can tell you it's higher then that.

At 10f or below I can raise my house temp at least 5 degrees with the fans on. I'm talking two rooms over and still hold the same temp in the stove room.

If we were to go by what you're saying and or SBI we would have to conclude that fans are just a market tool, profit maker deal and that only fools would buy them.

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This is from an SBI stove manual. 2% not 1%.
When used
regularly, the fan can provide a small increase in efficiency, up to 2 percent.

Fan help heat transfer efficiency but too much will cool off the box and you'll lose combustion efficiency. Together they make up the overall efficiency of the unit. Ideally you have to balance the amount of heat the fan moves off the stove. Maintaining a good secondary burn is important. It's like most things in life it's a balance--Ying & Yang. Upgrading a fan that the mfg. puts in the stove more times then not will lower the overall efficiency, but that doesn't mean no fan at all is better either. Keep the stove in it's sweet spot.

Grisu said:

Yep, and then you cool it too much, your secondary combustion stops working and you lose unburnt gases which are going up the flue.

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Secondary combustion stops? How would you determine what is "too much" for secondary combustion to stop.

If a 130 cfm fan would negatively affect efficiency - following your logic, then the EPA would NOT allow fans to be used as the fans would exacerbate the amount of hydrocarbons exhausted.

Secondary combustion will stop below 540 degrees(NON CAT stoves). It occurs between 540-1225 (roughly) depending on who you listen too. I'd say under 1100 degrees it would start to diminish. The stoves are tested with the fans that the MFG sells them with. I think the fan on the insert the OP was referring to is actually 120CFM. Which should be fine to operate with. IMO if they were to change the fan to say a 200CFM fan the efficiency could diminish.

madison said:

Secondary combustion stops? How would you determine what is "too much" for secondary combustion to stop.

If a 130 cfm fan would negatively affect efficiency - following your logic, then the EPA would NOT allow fans to be used as the fans would exacerbate the amount of hydrocarbons exhausted.

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See this EPA summary: http://nepis.epa.gov/Exe/ZyNET.exe/...ckDesc=Results page&MaximumPages=1&ZyEntry=55

Quotes from pages 36 and 37:
"A general drawback of this general technology is that by removing heat from the entire stove, firebox included, temperatures in the combustion chamber are lowered, which can reduce combustion efficiency."

"Fans are often used on fireplace inserts,.... However, it has not been shown that the fan will increase the net performance of a stove. This is especially true if a fan draws enough additional heat away from the stove to cool the firebox temperature and thereby decrease combustion efficiency."

SBI apparently concurs with the notion that blowers have a negligible impact on total heat output. Thus, I'll stay with my opinion that in general a blower will not help if the stove struggles to put out enough heat to keep someone's home warm.

I don't want to tell you to not use your fan; it's your stove and your home, do whatever makes you happy. I, however, enjoy the silence and the power savings.

Grisu,

Thanks a lot for that link, very interesting reading. Great find! Interesting that it was written in 1986 - which would be before the newer EPA rated stoves. Also of note in the summary on page three they qualify the report with some statements that there is not much data ... Obviously I have only quickly skimmed, but really interesting info.

- The only argument I was try to make and elucidate - which happens to be mentioned in that link on page 36, second paragraph, third sentence - is - paraphrased: that heat transfer is a function of the velocity of the gas over the heat exchanger. And in my personal situation - large volume home - using mainly a convective type stove (pe-t6) a blower does work, albeit with an increase in electrical cost.

-Otherwise, I agree with most of your observations and comments.

Again, very cool link. Thanks

madison said:

Grisu,

Thanks a lot for that link, very interesting reading. Great find! Interesting that it was written in 1986 - which would be before the newer EPA rated stoves. Also of note in the summary on page three they qualify the report with some statements that there is not much data ... Obviously I have only quickly skimmed, but really interesting info.

- The only argument I was try to make and elucidate - which happens to be mentioned in that link on page 36, second paragraph, third sentence - is - paraphrased: that heat transfer is a function of the velocity of the gas over the heat exchanger. And in my personal situation - large volume home - using mainly a convective type stove (pe-t6) a blower does work, albeit with an increase in electrical cost.

-Otherwise, I agree with most of your observations and comments.

Again, very cool link. Thanks

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Thanks, Madison. I was looking for the study mentioned earlier but found this one instead. Agree, interesting read. Since it talks a lot about secondary and catalytic burn I assume it actually refers to modern EPA-stoves. Will have to read through it at some other day, though. However, I think it essentially agrees with my point that at a given air setting there is an optimal temperature (range) for complete combustion. The blower can help avoiding temps that are too high but at some point may become counterproductive when it cools down the stove too much. Probably the reason that modern stoves have relatively "weak" fans. Would be interesting to see a real study with different current stoves models to really judge the impact of the blower on efficiency. But we should not forget that increased efficiency means less heat goes up the flue, which will impact draft. We all advice against "Magic Heat retainers" but then claim a blower is a good thing? Hence, another reason why I not believe it gives you a significant amount of additional heat. The other question I would have at least for a stove: How much does a fan really increase the air velocity over the stovetop surface compared with the convective current that is happening anyway? If it has not been done yet, that would be an interesting area for some basic research to improve the design of modern stoves. Maybe the guys from the U of Maryland would be into that. .

madison said:

Secondary combustion stops? How would you determine what is "too much" for secondary combustion to stop.

If a 130 cfm fan would negatively affect efficiency - following your logic, then the EPA would NOT allow fans to be used as the fans would exacerbate the amount of hydrocarbons exhausted.

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I have never seen my cat go out because of the fans..lol.

Ok,my stove was filled maybe a little better then half last night. Around 8pm. Anyways it was on as low a t setting as it could be.
There was still some wood in there with a nice coal bed. Stove top was 400 mostly all over the top because the cat aint doing much at this point.
I just ran the blower on high for 45 mins. I rechecked the stove top and it's down to 350..yep,the fan really cooled things..lol.
These temps are from a IR temp gun.

Btw,next room over went from 72 to 75f.