How Does a Wood Stove Fan Work?

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HOW DOES A STOVE FAN WORK

If there is one item that can make a dramatic difference to the use your get out of your wood burning stove, a stove fan is definitely it.

They serve to blow the warm air produced by the stove around the room or into another room, depending on where you point it, in effect maximising the heating power of the stove.

Stove top fans do this by making the most of the rising warm air produced by the stove, preventing it from staying trapped on the ceiling, by redistributing it around the room. This makes your room much warmer and comfortable and helps to lessen the amount of wood that you burn.

Without a stove fan, the warm air is not going to be distributed around the room equally, meaning you’ll need to sit close to the stove to warm up. More often than not, most of the heat is lost to the outside through the piping or up the chimney instead of keeping your living space a cozy temperature.

It’s worth noting here, that stove top fans can also be used with pellet stoves too!

Wood Stove Fans and Blowers

As well as wood stove fans, there is also the option of using a blower. People often use stove fans and blowers interchangeably but they are two completely different things that aim to achieve the same goal – redistributing the air warmed by the stove.

A wood stove fan has 4 to 6 blades, typically made from aluminium and it sits on top of your stove, circulating and blowing the air in the direction you point it. There are two main types of stove fan which work differently, but we will go into this in the next section.

Blowers are made from heat resistant tubing and go directly inside your stove. Air from the room is taken into the tubing which is then heated up and distributed from the stove back into the room.

Unlike a wood stove fan, this is not a passive process. The air intake of the blower requires an electrical outlet to run. Many wood stoves you can buy come with a blower already installed but when compared to the effectiveness of a stove fan and the noise levels, often people find there is no comparison, the stove fan wins every time.

Being so affordable, yet effective at their job, stove top fans save you money on your heating bills by taking away your need to put on the supplementary heating and also burn less wood. But what is it that makes a fan so effective? And for those that are interested, how does a wood stove fan work passively?

How a Wood stove Fan Works: The Science

As mentioned above, there are two types of wood stove fan which do not need an external power source or a battery but operate by using different fundamental principles to generate the energy they need to spin the blades from the heat of the stove. There are TEG stove fans (thermoelectric generator) and SE (Stirling engine) fans, the former being the most commonly used of the two.

TEG Fans and the Seebeck effect

The TEG fan uses a thermoelectric module that utilizes a positive and a negative electrical semiconductor. When heat is transferred between the hot stove to the cold fan, the differentiation in temperature results in an electrical current.

This principle is known as the Seebeck effect. A phenomenon where a differentiation of temperature between two different semiconductors causes an electrical current.

This current is sent through the wires on the fan into a rotary motor which then spins the fan blades.

These fans are most popular as they are safe and reliable with minimal moving parts and completely reliant on the heat produced by the stove for energy. You can find popular stove fans such as the Voda 4 blade on Amazon through this link.

Stirling Engine Fans: Cyclic Compression and Expansion

As stated, the Stirling engine uses the heat from the stove to move two pistons, which in turn operate the fan blades.

One portion of the engine is exposed to cool air, whilst the other is exposed to the hot air generated by the stove. The expansive hot air causes one piston to contract while the cold air causes the other piston to retract.

The pistons carry on contracting and retracting alternatively, continuing this motion which drives a rotary motor resulting in spinning fan blades. See the below animation to get a better view of this in action.

Even though Stirling engines are highly efficient, they are chunkier, more expensive and have more moving parts than the TEG fans. This means there is more chance of something breaking and an increased need for maintenance if you purchased a bad model.

With that being said, Stirling engine stove fans are far more powerful, run quieter, and are just impressive little devices to look at. The best Stirling engine wood stove fans you can find are no doubt those made by Warpfive Stove Fans, which even come with a maintenance kit – found on Amazon here.

Temperature Requirement

Now given that both types of stove top fans do require only the heat of your stove to work, they will have a minimum temperature to get going. This minimum temperature can vary between manufacturer depending on the materials they use to make the blades and how good their semiconductors are.

  • For TEG fans the minimum temperature is between 150-200F (65.5- 3C)
  • For SE fans the minimum temperature is between 158-200F (70-93.3C)

Once the minimum temperature is reached, the fan will not be spinning as fast as it can and the hotter the base of the fan gets, the faster the blades will spin until they reach a maximum rotary limit.

This is also where it will reach is maximum cubic feet per minute (CFM) which on average is around 240CFM.

Stove Fan Placement and Safety

Just as a final note on this article, we will go over some stove fan safety and placement tips.

You can point the fan in any direction that you want. Perhaps you would prefer it to point towards an open hallway to help warm other rooms in the home, or towards a wall so that the heated air bounces off and mixes with the cool air in the room.

What matters is where you place the stove fan for safety and maximum efficiency. The first port of call is to ensure that the fan is placed on a flat surface on the top of your stove. Also, make sure that it’s away from your flue pipe!

It would work at its optimal efficiency in the middle at the very back edge of the stove where the cool air can be drawn in from behind and mixed with the warm air to then be dispersed around the room.

Once the fan has started going, never touch it or move it. The base of the fan could be extremely hot and can cause burns. Let it cool before moving it and be sure you are not placing it on an unprotected surface. It’s also always wise to keep it away from children, especially when in use.

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