Lets talk about integrated fans

[Poindexter]

Not box fans down the hallway, the fans manufacturers put on our solid fuel burning devices.

Love them, hate them?

Too loud? Subjective I know.

Not effective? What data do you have?

I am going to let this go until a little bit before I answer my own questions. Hopefully Saturday-ish, I have some things coming up. Doesn't matter if you have a 1976 Heatilator or a Jotul made summer 2020, what do you think/know about these things?

 

[Gearhead660]

Having 3 young kids, I prefer the quiet. With an insert a fan is a must. My insert fan is too loud in my opinion. Also not enough cfm for the noise it creates. Tried the fan on the Myriad, decent air flow for the little bit of noise it makes. Think I will only use the fan on it when it gets bitter cold out and need the extra heat.

 

[James02]

The fan on the BK is "meh" at best.. noise doesn't bother me but it isn't bad IMO..

 

[Bad LP]

I have a Jotul insert. I realize the fan is a necessary evil but I'm not understanding why it's so loud. Thankfully it is a variable speed so I run it at about 80-85% and that helps a great deal. I also just turn up the volume on the TV a little and the problem is solved.

 

[firefighterjake]

Jotul dealer suggested that I wait and see if I needed a Jotul fan on my stove when I asked about buying one . . . said if I felt I would need it I could always buy it later. Really respected that dealer since he could have very easily just taken my money. Never did go back and get a Jotul stove fan since I found the floor fan trick worked just fine.

 

[Highbeam]

Any noise is too much noise. I don't run mine unless I think it is needed which is when I let the stove go out and the house got cold so I need more heat output for rapid catch up. I do believe that they are effective but I don't need that effect very often.

I don't know why they are so loud. It's not the rushing air. Engineers should be smart enough to make them quiet.

 

[captrick]

I actually was wondering the same thing...we have a fan on our old wood stove downstairs...we never use it. We've never needed it. That thing puts off a ton of heat. I'm not having an outlet put in where our new Wood Insert is going upstairs...simply because I don't really think we'd use it. I have a ceiling fan I keep on low to push the heat down from the peak anyway...and my real desire for the new wood stove is more about keeping the fire going and producing "heat" where the open fireplace just doesn't. We have a plug right next to the hearth if I feel like I really want to plug it in at some point (comes with the VC Mont II)..

 

[Dataman]

I had BK King. Fans were noisy. And I replaced one of them. Still Noisy. Small fans trying to move large air. I only used them at night and when very cold. Couple box fans in the hall were lots quieter and more effective. I have ceiling fan on low running backwards. Switched to Pellet Stove. The fan in that is lots quieter. (Harmon XXV). On Medium it's not that noticeable.

 

[begreen]

Our stove is in the living room so I like quiet. Fortunately, it convects pretty well throughout our open floorplan, so in milder weather we leave it off. When it gets very cold out though, I turn the blower on, usually at low to medium-low speed which is not silent, but it's still at a very low noise level. Low enough that the TV does not have to be turned up to compete with it. Even on high it's tolerable. I just tested it with a db meter. At 6 ft the room ambient noise was 35db. With it on medium-low it was 41db, and on high it was 48db.

 

[fvhowler]

No fan on my freestanding wood stove. I just don't see the need. I prefer the quiet, radiant heat and let ceiling fans move air around.

 

[WinterinWI]

Any noise is too much noise. I don't run mine unless I think it is needed which is when I let the stove go out and the house got cold so I need more heat output for rapid catch up. I do believe that they are effective but I don't need that effect very often.

I don't know why they are so loud. It's not the rushing air. Engineers should be smart enough to make them quiet.

I'm surprised more effort hasn't been put into this. I'd be willing to pay twice as much for something half as loud. I can't be the only one.

I'm sure it doesn't help that my stove is jacketed. Seems to act as an echo chamber amplifying the noise the fan does make.

 

[begreen]

If everyone wrote to their stove companies and asked for the noise level to be posted on their website under the product specs maybe they would get the message. Our stove is jacketed and at certain times and blower setting they can resonate with the blower vibrations. Or it might be the rear plenum. I have heard this happen with our blower on medium-high. Odd thing is that it may happen after a couple hours of running, or not at all. The fix is just to turn down the blower speed to medium, but it is curious. It may have to do with the mass of the fire? Nikolai Tesla was a master at understanding this stuff. He seemed to intuit the innate resonant frequencies of objects.

 

[Grizzerbear]

If I am home alone.....the fan is pretty loud on high. That being said with three kids in a 1500 sq ft house the fan on my stove has never been the issue of getting peace lol. I can't sleep without the sound of a fan going anyways so it doesn't bother me and I find that having my fan on medium is about perfect anyhow. Turning the fan on high vs low makes a big difference on cooling the stove down which is useful to me.

 

[nahiker]

Forget what make/model insert I have but the noise from the fans doesn't bother me and moves quite a good amount of heat. A far running backwards moves the air upstairs to the main floor, really only gets cold after the night fire has burned out. Definitely don't mind the fan haha. I'm wondering if I can put those stove top fans on the top of the metal firebox if the insert to move more air.

 

[Agent]

Personal observations tell me that stove fans are effective at removing heat from any given stove.
1970's Big Buck - Englander NC30 - BK Princess
All provide(d) better heat using the built in fan.

Noise wise, also somewhat similar. That's not terribly surprising to me, considering that these are small form factor fans moving air at a high rate of speed over a rough surface. Even running at lower speeds for noise control helps immensely compared to no fan at all.

 

[PaulOinMA]

Lopi Answer insert. I use the fan. Have it turned down lower than I used to. More air contact time.

 

[ABMax24]

Our stove is jacketed and at certain times and blower setting they can resonate with the blower vibrations. Or it might be the rear plenum. I have heard this happen with our blower on medium-high. Odd thing is that it may happen after a couple hours of running, or not at all. The fix is just to turn down the blower speed to medium, but it is curious. It may have to do with the mass of the fire? Nikolai Tesla was a master at understanding this stuff. He seemed to intuit the innate resonant frequencies of objects.

My Osburn does it, so does my parents PE Super 27. Conclusion we have come to is it has to do with the temperature differential between the firebox and sheet metal jackets causing different forces within the sheet metal, which seems to change the resonant frequencies of the material. Usually changing the fan speed on mine makes it go away, but once and a while it stays from low to high, in which case a gentle open palm hit to the vibrating sheet metal usually stops it.

I think manufacturers are stuck in a hard place on fans though, Ideally a larger lower speed fan would make it quieter, but then where do they put it, particularly on inserts.

 

[ABMax24]

Lopi Answer insert. I use the fan. Have it turned down lower than I used to. More air contact time.

Although intuitively your theory sounds correct, it's actually the opposite. Higher velocity promotes higher heat exchange rates because of higher turbulence and higher flow rates to remove more heat from the stove top.

I learned this the hard way on an engine heat exchanger for my jet boat. I built this large aluminum exchanger that slowed the engine coolant and river water right down to allow more heat exchange time, the flow was never turbulent enough to actually allow the heat to transfer. The coolant returned to the engine still hot and the river water left only slightly warmed. The new design is 1/3 the size with very small spaces between the plates promoting high velocity through the exchanger. It transfers at least twice the heat of the old design.

Often less understood, is the effect of velocity on the thermal transfer characteristics of the heat exchanger: It turns out that the higher the velocity through the heat exchanger, the higher the turbulence — and the higher the turbulence, the more efficient the thermal transfer.
You may be wondering how that can be. The answer lies in the turbulence of the flow.
You’ll recall that turbulent flow creates a great deal of disturbance along the flow path. This turbulence forces the fluid against the walls of the heat exchanger and increases the friction between the fluid and the surface.
The turbulence constantly pushes fresh fluid against the metal wall, and the greater the volume of fluid in contact with the walls of the heat exchanger, the greater the thermal transfer.
The opposite of turbulent flow is “laminar flow,” which you may also recall is defined as a smooth, linear flow through the system. As turbulence falls, the film on the walls of the heat exchanger increases. Called the “film coefficient,” as it increases, the thermal transfer efficiency is reduced.

Heat Exchanger Fluid Velocity – Why Should I Care?

The heat exchanger is the core device in almost every fluid temperature control system. But properly selecting a heat exchanger is a daunting task.

blog.viscosity.com

).

 

[Fod01]

Our flush insert requires the fan to get the heat out. The squirrel cages were quiet at first, but tended to get a bit rattly as time went on.
You clean them, try to lube the bearings, and hope for the best. Don't forget about power-failures if you're really using it for heat. A free-stander would've been nice.....

 

[Mech e]

I don't have a blower on my stove, so I don't know how they are mounted. Do they use any type of dampening material between the blower and the stove jacket? If not, I might try some high-temp silicone rubber sheet between the blower and the jacket. I would also put some under the mount screw heads. You would still get flow noise, but the mechanical noise that gets transferred to the jacket would be reduced. This is most likely the source of resonance.

 

[fvhowler]

As someone who's burned with an insert and freestanding woodstove, I found the insert required a fan/blower to get more heat from the stove. A well-placed free standing wood stove which I currently use, does not need a fan to effectively heat the house.

Everybody's setup/situation is different. Go with what works for you.

 

[PaulOinMA]

... Although intuitively your theory sounds correct, it's actually the opposite ...

Not sure that's applicable. The path from the fan through the five air gap sides of my insert are not a smooth surface.

 

[ABMax24]

Not sure that's applicable. The path from the fan through the five air gap sides of my insert are not a smooth surface.

Doesn't really matter, the higher velocity still helps to reduce the thickness of the boundary layer next to all surfaces. The higher mass flow also enables the air to pull away more heat, the air temp coming off the stove may be lower at a higher blower setting, but because of the increased flow rates more total heat is still being removed from the stove.

 

[PaulOinMA]

Any data on that as it applies to inserts?

 

[ABMax24]

Any data on that as it applies to inserts?

You can find out for yourself, get an IR gun and measure the stove top temps with the same fire with; blower off, on low, and on high. The stove top temps reflect the amount of heat being transferred to the air and into the room, the more heat being transferred the lower the stove top temps.

Blower off will be the hottest.
Blower on low will be in between.
Blower on high will be the coolest.

The trick to this will be maintaining an even enough output from the firebox to conduct the test.