Wood stove fans

[Steve Thomas]

I've had them for years, actually I have two on the main stove in the lounge. Several others having brought one, thanked me for the idea.
Instead of the heat just going up the chimney breast and across the ceiling it's gently circulated silently around the room.
The physics is very simple of a thermoelectric module (the thin wired sandwich). Heat up one side and cool the other, you get a voltage across the sandwich to run a fan. Conversely if you applied a voltage to it, one side would get hot, the other cold, (I've heard for a cold drink dispensers).
Cheap ones from lidl of Aldi are just as good as expensive, the components cost peanuts. One of mine must be at least 15 years old.

 

[johnnyb]

A very simple test using a burning spill illustrates it well enough. Of course a bigger powered fan will spread the air better. But will be noisy and cost money to run. Anyone whose accidentally stuck there fingers in a stove fan will attest to the power on a stove at full chat (which is how Roy Sutton lost his finger, not on a spindle with a square block but a handheld fan wadkin made to clear shavings from machinery, you couldn't write it)

 

[squib]

Great piece of kit that evens out the temperature in rooms, especially if the room is long or the stove is tucked in a fireplace.

 

[John Brown]

Google's AI reply says they can increase your stoves efficiency by up to 30%, but the linked citation is from a stove top fan seller's page.
I'm slightly sceptical, as I know that Peltier effect devices are very inefficient, but maybe there are circumstances where these fans can help. I do wonder whether some sort of baffle might work equally well in some cases.
I also wonder if part of the appeal is the something for nothing/free power gadgetry aspect.
I don't own one, the grandchildren would chop their fingers off in a jiffy, and I'm not claiming to be any sort of expert, just interested.

 

[Phil Pascoe]

I had a couple on different stoves - a total waste of space. They look as if they're doing something, I think that's part of the appeal.

 

[Terry - Somerset]

A completely uniformed but (I think) logical approach to the question. My only experience of a wood stove is in a cottage rented for a year following a job move.

As a Peltier effect fan runs on "waste" heat I am not sure how it can be "inefficient" - the worst is that it fails to move the heat as fast as desirable. If completely ineffective, the cost of the device would have been wasted - it would make no difference to the output of the stove.

A fan will increase and change circulation patterns from those created by convection and draughts alone. It is likely the temperature across the total space will become more homogenous. It is just plausible it could set up a different but static circulation unless the fan oscillates.

By moving more air across the stove and flue, the temperature of both will fall. Whether this affects the combustion process is unclear - airflow to the stove and the combustible material inside is unchanged. Flue efficiency and maintenance may be affected if the temperature falls too far.

A real impact on efficiency is that lower temperatures close to the stove would reduce heat loss through the walls in that area, possibly offset by higher temperatures elsewhere in the room increasing external heat loss.

 

[Krome10]

I tried one a couple of years ago and didn't feel it made a difference for me (or the wife for that matter).

Nearly everything I read about them - and heard anecdotally - had me thinking the effect would be obvious and large. But I didn't feel any difference subjectively, nor did the thermometer on the coffee table in front of me seem to behave any differently with or without the fan. I didn't use the thermometer in any kind of systematic way, but being quite familiar with how quickly the room heated without the fan, I kept an eye on it for any changes and didn't note any.

I had a slight bias in so much as I don't like the aesthetic. But I do think I'd have happily to put that aside if it meant being able to remove hat and scarf sooner!

With regards normal (non-stove top) fans, the consensus seems to be to place them away from the stove pointing toward the stove. If the objective is to heat an adjacent room, it's best placed near the doorway to that room, blowing in the direction of the stove. Haven't tried that myself though, so just based on what I've read.

 

[denmans]

Well it would move hot air sideways a bit and may cool a small portion of the stove quicker as suggested but it will also use up energy, purely by moving round. Work will have to be done by the heat of the fire to lift the blades, overall making less heat available to heat the room. No such thing as perpetual motion.

 

[Jacob]

Well it would move hot air sideways a bit and may cool a small portion of the stove quicker as suggested but it will also use up energy, purely by moving round. Work will have to be done by the heat of the fire to lift the blades, overall making less heat available to heat the room. No such thing as perpetual motion.

As far as the air in the room is concerned they are energy neutral - taking heat from stove and turning it into kinetic energy in the air movement, which then reverts to heat through friction as it is obstructed and reduced.
It's more about distribution.
One pleasing thing I've noticed with our newly fitted stove is that at same temp as per thermometer the room feels warmer than with the central heating from radiators. Sounds unlikely but if not a delusion I think it could due to the much higher temperature of the small stove causing a stronger current circulation than larger area cooler radiators.

 

[duke]

Tomorrow I am giving them a visit and will then provide a photo. He can't seem to send one to me via text! Well he is pushing 90 years of life.

To the right is the fan control and left side is the switch for the inline vent to another room.

 

[Robbo3]

A complete waste of time and space, we now use a small electric fan to move warm air around.


what make / model ?

Dunno. £15 from Amazon.
If we leave the living room door open the heat will gradually seep through the hall to other areas without the fan but with it, we can open the doors to other rooms to get them comfortable. Depending on the accuracy of my digital thermometers (living room, kitchen & hallway) 20°C is the norm.

I had a couple on different stoves - a total waste of space. They look as if they're doing something, I think that's part of the appeal.

Yep, not much use in my drafty concrete garage but brilliant in the house.