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.

 

[Jester129]

So how do I go on with an open fire in a fireplace, what is best please?

 

[Phil Pascoe]

Get rid of it.

 

[Stevekane]

We have a stove in a large inglenook, lidl stove fan placed towards the back of the stove as recommended in the instructions. We continue to use it although I cannot really feel any difference, and several times over the yesrs Ive held thin stips of tissue paper in front of the fan to see if I could detect much air movement, and if I can its not much, I think any “push” from the fan is going to struggle against the air rising off the stove. I suspect that a small electric fan would be more powerful and could have a positive effect on convection if heating a larger/longer room.
Steve

 

[Phil Pascoe]

I had an electric fan blowing across the front of the stove in along room, and a 4" fan just below the coving at the other end of the room blowing out into the stair well. In the winter when both fans had been on for while the difference upstairs was noticeable, had I stayed in the house I'd have changed the 4" fan for a 6" one. It doesn't really apply now as I have an insulated 6" duct running from the ceiling above the stove to an inline fan and a Y piece taking the excess heat down into the other side of the bedroom and kitchen

.

 

[Agent_zed]

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

But stove top fans are small electric fans moving warm air around? With the added advantage that I don't have to plug them in, change batteries or worry about turning it on.

I've got a cheap von haus one and it sits and does what it does. I do also have a large aluminium cooling block i took off an old PC which I put behind it as that will transfer a lot of heat energy quickly.

I think one of the biggest factors in circulating hot air from a stove/fire is a mantel piece. I haven't looked it up but I would guess that this is the entire point of a mantel piece. The hot air hits it and is forced out into the room, rather than straight up to the ceiling. Exactly the same job as a radiator shelf.

I would guess that if you have a stove out in the room with no mantel then a stovefan would potentially be more beneficial than for fires with mantels, but I have no proof of this.

 

[trvlr]

I have two - standing at the rear of the of the stove top; one each side of the flu pipe. Both Peltier effect driven; low - i.e. - no maintenance.

Bought one to test and satisfied with results bought the second.

I can feel the modest "draft/air flow" they create (warmer air pushed out of the alcove wherein stands the stove) if I pass my hand across the respective air flows; and can confirm it too with soft tissue or similar passed across the front of each fan once it gets going.

Very effective - as they push the warm air around the room (25 x 15ft) and certainly a noticeable effect. Prior to their installation (they simply stand on the stove roof) the far end of the room wasn't as warm as now (once they kick in). Much less trapped heat within the alcove (not much by a long shot...).

My chimney sweep approves and does advise to use them.

Got mine from that big river company and they cost not much.

 

[Hypnotic Chimera]

I love mine.
It works.
It's subtle, but the effect is definitely there.
I think it definitely does depend upon fireplace type and room layout for the extent to which they are beneficial, and in some cases they aren't "necessary".

For our layout - it is a protruding inglenook style brick fireplace in the centre of the long living room wall - and the wall is an external one. Two other living room walls are external - one of which is wooden French doors. This makes the living room the coldest room in the house.

The stove is pretty much the smallest available - at only 4.5kW output.

There is a very large enclosed cavity above the stove and behind the oak beam mantle -and this is a heat capture zone.

With the heat-activated fan it only works and is automatic when the stove top begins to heat up, so it prevents the cavity from trapping the early heat and keeps the heat-trap air cycling over and spreading into the room, instead of simply gathering in the cavity, filing up, and spilling out from under the mantle and convecting straight up to the ceiling. The room would eventually reach a similar equilibrium without the fan in place, so it doesn't produce "more heat" - it just helps to spread the warm air around more easily and reaching equilibrium sooner.

It's only a small fan. Cheap too, but it definitely does do some good in helping warm the room "sooner"...

 

[Jacob]

I love mine.
It works.
It's subtle, but the effect is definitely there.
I think it definitely does depend upon fireplace type and room layout for the extent to which they are beneficial, and in some cases they aren't "necessary".

For our layout - it is a protruding inglenook style brick fireplace in the centre of the long living room wall - and the wall is an external one. Two other living room walls are external - one of which is wooden French doors. This makes the living room the coldest room in the house.

The stove is pretty much the smallest available - at only 4.5kW output.

There is a very large enclosed cavity above the stove and behind the oak beam mantle -and this is a heat capture zone.

With the heat-activated fan it only works and is automatic when the stove top begins to heat up, so it prevents the cavity from trapping the early heat and keeps the heat-trap air cycling over and spreading into the room, instead of simply gathering in the cavity, filing up, and spilling out from under the mantle and convecting straight up to the ceiling. The room would eventually reach a similar equilibrium without the fan in place, so it doesn't produce "more heat" - it just helps to spread the warm air around more easily and reaching equilibrium sooner.

It's only a small fan. Cheap too, but it definitely does do some good in helping warm the room "sooner"...

Mine arrived. Vonhaus. £20
It seems to work, much the same as HC's above. Much stronger when the stove is hottest, and can feel the draught.

 

[Agent_zed]

Out of interest I took more note of mine since reading this thread. I had a till receipt in the burn pile so i held it vertical and lowered it in front of the fan and it was blown to a 40-45degree angle as there was quite a draught.

It's no where near as powerful as a desk fan for example (they are about 30watts) but it certainly moves some air.

If nothing else it's useful to look into the room and see if the fire is still hot, as it will be running slower if the fire is going out.