Losing heat up the flue with a Lopi

trguitar · Feb 10, 2013

I hear in many comments on this forum about it not being good running a stove with air control wide open because you lose a lot of heat up the flue.

I've been trying to understand this in relation to my Lopi stove, and I don't think it applies.

The Lopi has a by-pass at the top of the stove which you use when you open the door. The by-pass opens a slot at the top of the firebox which lets all the smoke and gases directly up into the flue. But, this by-pass has nothing to do with air control.

The air control knob is at the bottom of the stove.

So, my question is this: If I run with the by-pass closed and the air fully open, I am not losing tons of heat up the flue, right? The fire is still being forced to run through the firebox, down the airwash, etc. I may be burning up my wood faster, but I'm not losing heat.

If I am wrong about this would someone please explain it.

Do other stoves not have this by-pass feature?

webby3650 · Feb 10, 2013

Some other stoves do have a by-pass, but it's not that common on non cat stoves.
With the by-pass closed and the air control on high it makes a great fire, so big in fact that it loses efficiency. With the air on high it rushes a lot of air into the firebox and in turn, up the flue. The longer that the gases stay in the firebox the more efficient it is. So, by reducing the incoming air, the smoke stays in the box longer, making a more complete burn and a much longer burn.
My Freedom reaches the highest temps after the air is reduced to half. Do you use a thermometer? With good dry wood you should see the same results.

begreen · Feb 10, 2013

If you have the air control wide open, with a fresh fire you are sending hot, unburnt wood gases up the flue. The reverse starts to happen as you close down the air supply. Restricting the primary air, once the fire is going, allows the draft to pull harder on the secondary air supply, through the burn tubes. Secondary combustion burns the wood gases much more completely resulting in a hotter stove and a cooler flue. You definitely want to shut down the air until the flames get lazy and wafting. That will provide much better heat from the stove.

trguitar · Feb 11, 2013

This makes sense. Thanks guys.

oldspark · Feb 11, 2013

begreen said:
If you have the air control wide open, with a fresh fire you are sending hot, unburnt wood gases up the flue. The reverse starts to happen as you close down the air supply. Restricting the primary air, once the fire is going, allows the draft to pull harder on the secondary air supply, through the burn tubes. Secondary combustion burns the wood gases much more completely resulting in a hotter stove and a cooler flue. You definitely want to shut down the air until the flames get lazy and wafting. That will provide much better heat from the stove.

Cant heat my house that way, I have to give it more air than that if it is really cold out, lazy flames in some cases means cold house.

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Losing heat up the flue with a Lopi

trguitar

Feeling the Heat

webby3650

Master of Fire

begreen

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trguitar

Feeling the Heat

oldspark

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