My probe thermometer at resting state

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Split

Member
Aug 28, 2022
128
Nova Scotia, Canada
So, I have a lovely PE Classic LE. It tends to burn hot. I see posts on here about fluev emps and mine are always way over what others have. When I start a fire my flue gets hot fast (top down/bottom up it don't matter). In order to let my cold starts get going the thermometer generally gets up to around 1200° (I'm double wall). It then slowly goes down and stays at a solid 900° for the majority of the burn cycle and then dies down over the next few hours. My secondaries on this stove can really get going but not if I shut my stove down too early due to a high flue temp.

According to WoodHeat.org flue thermometers should not be used and that they lead to improper stove usage. Here is a quote from the site:

It turns out that there is no correct operating temperature for wood stoves because their output is modulated to provide enough heat for the conditions. So, in cold winter weather the temperature will be higher than in the fall when the heating load is lower.

"Also, each new load of wood should be fired wide open until the firebox is full of flame and the wood is charred and the edges are glowing. That will produce a high flue gas temperature. Then you might set the air control back for an extended burn, so the temperature will fall. And, as the wood load is consumed the temperature gradually falls until it is time to reload.

For most of the time a wood stove is operating, its flue gas temperature is either rising or falling. Anyone who says that you should aim for a particular flue gas temperature or even a range in temperature is setting you up for failure because steady-state burning is almost impossible to achieve.

The correspondence we see from visitors to woodheat.org convinces us that thermometers cause more confusion than clarity. People try to make their stove operation conform to the markings on the dial of a cheap thermometer or to the recommendations of someone who really doesn't know much about wood heating."

Obviously my flue Temps have me worried. Yet my stove burns well. I like what WoodHeat.org is saying and don't want to live and die by a meter. I'm wondering if my thermometer is reading correctly. It's installed by a WETT certified installer. At a resting state of room temp it does not go down to zero. It stays around 250°F. Could that mean it's off by 250°? Not a thermometer expert.

To install a new thermometer in the flue just pull this one out and stick another in the drilled hole?

I'll be going to my dealer tomorrow to discuss key dampers and other options.

Thanks for your thoughts.

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Todd

Minister of Fire
Nov 19, 2005
9,875
NW Wisconsin
Looks like your thermometer is off. Try to adjust it to room temp then reinsert and try again.

I disagree with woodheat.org. Thermometers are an essential tool for wood burning and helps you fine tune your burn.
 

begreen

Mooderator
Staff member
Nov 18, 2005
97,901
South Puget Sound, WA
As much respect as I have for woodheat, I fundamentally disagree with some of these statements, but that could be because they are taken out of context. I and many others run their stoves almost exclusively by the flue temps. On our stove, the stovetop temp is only consulted occasionally.

Of course flue temps will decline over time, right along with stovetop temps as the fire dies down. But letting the flue go over 1000º for a long time is a great waste of fuel and puts more stress on the stovepipe.

When burning dry wood and with the stove dialed in, our loads don't vary much in behavior. The flue temps recorded with the digital probe are consistent load after load. It's only when I don't turn down the air enough that I get a high flue temp. This thread shows how a full load behaves and how the flue temps guide the air control setting.

There are some factors that can cause high flue temps in your stove. Too strong draft, warped rails or baffle, side insulation missing or in bad condition are amongst them. The other possibility is that the thermometer is no longer accurate. Our Condar probe is old and needs replacing, but it reads low and slow. I have found that the digital thermometer is a much better tool than the mechanical probe thermometer. It reacts instantly which helps much more in seeing how air control changes affect the flue temp.
 
Last edited:

stoveliker

Minister of Fire
Nov 17, 2019
6,483
Long Island NY
I agree that aiming for a constant flue temperature is often not correct. In my view the flue thermometer is a tool that tells me when I'm out of the proper (safe) operating range.
It's the (a) red signaling light for when things go wrong.

Also, aiming for as low flue temps as possible, while keeping it above the safe minimum, and while getting to the right room temperature (!), allows one to burn in the most efficient way.
 
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