Large Difference in Stovetop and Flue Temperatures

[bdl]

Thank you for your help as we learn in our first year burning.

There's a huge difference in our stovetop temperature and flue temperature. When I have the stove top around 550 or so, the flue is closer to 200. These are both the magnetic thermometers that sit on the pipe/stovetop. I've tried switching them too, just to make sure one isn't busted. It's almost impossible to get the flue temperatures into the non-creosote zone.

This makes me worry about creosote, but at the same time, I also feel I can't be burning the wood stove at 700 on the stove top all of the time. It's a VC Defiant 1610 Non-Catalytic.

Any advice would be much appreciated.

 

[Ludlow]

What kind of connector do you have?

 

[Grizzerbear]

Im guessing you have a single wall flue? A magnetic thermometer on single wall will read roughly half of what your actual flue gases inside the flue are. So double the numbers on the thermometer to get your temp which would be 400ish

 

[bdl]

Thank you both for your replies. I'm sorry that I'm such a novice--we bought the house with it all installed, so I'm not actually sure if what kind of connector or if it is a single wall flue. How do I tell? I've attached a picture in case it helps.

 

[Ludlow]

Do you have a fan blowing on the stove?

 

[bdl]

Do you have a fan blowing on the stove?

No.

 

[Ludlow]

Looks like the fire is in coals and that is where my pipe temp is at that stage. Does it get into the upper burn range early in the cycle when the flames are active?

 

[bdl]

Looks like the fire is in coals and that is where my pipe temp is at that stage. Does it get into the upper burn range early in the cycle when the flames are active?

Even in the earlier stage in the cycle, it doesn't really want to get above 250.

 

[Ludlow]

Well, let's go to the default question. Tell us about your wood. What kind, how long has it been seasoned, is it cold when you put it in the stove, etc?

 

[bdl]

Well, let's go to the default question. Tell us about your wood. What kind, how long has it been seasoned, is it cold when you put it in the stove, etc?

The wood is extremely dry hardwood. It's been sitting in the house for at least a day. It burns hot and rather fast.

 

[Seasoned Oak]

That sounds about right. Your gauge is pretty high up on the pipe too. There is also quite a difference in temps from where the pipe exits the stove to where it goes into the chimney as well.

 

[Ludlow]

That sounds about right. Your gauge is pretty high up on the pipe too. There is also quite a difference in temps from where the pipe exits the stove to where it goes into the chimney as well.

I can attest! Try lowering the gauge about 4" and see what you get.

 

[Grizzerbear]

Your flue temps....once the stove is up to temp and cruising....will be fairly close to your stove temps. Meaning if your stovetop temp reads 500 or what have you your flue thermometer will probably be around 250....which actual inside of flue would be around 500. It reads around half of actual temp because it is measuring the wall of your connector unlike a probe thermometer that is reading inside of the pipe.

It burns hot and rather fast.

What do you usually have your primary air set at. How big of splits.

 

[Ludlow]

Might 8" connectors run cooler surface temps?

 

[bdl]

Your flue temps....once the stove is up to temp and cruising....will be fairly close to your stove temps. Meaning if your stovetop temp reads 500 or what have you your flue thermometer will probably be around 250....which actual inside of flue would be around 500. It reads around half of actual temp because it is measuring the wall of your connector unlike a probe thermometer that is reading inside of the pipe.

What do you usually have your primary air set at. How big of splits.

After closing the flue, I usually bring the air gradually to about halfway. The splits seems to be about 3–4 inch splits. But if what you say about it being double the actual inside temperature, then things actually sound like they are pretty even. That's probably the reason, and I had no idea that the outside of the pipe is half of the inside. Thank you so much for your help!

 

[Grizzerbear]

Im on a phone so i cant see pics very well. What is the stove.

 

[Ludlow]

VC Defiant 1610

 

[Grizzerbear]

VC Defiant 1610

Duh stupid me. Forgot in was in first post.

 

[jsdashoes]

I had a VC Resolute Acclaim for years. Kept the thermometer on the griddle and always got really consistent/accurate readings.
Agree with prior post, for pipe temps you're a bit high. I think 18" up from the collar is what I've read.

 

[begreen]

250º surface temp on single-wall is about 500º interior temp. That's a good temp to see there during the wood outgassing (flaming) stage. During the coaling stage, it's ok if it drops lower. You could try moving the thermometer to 18" over the top of the stove to see if that makes a difference. You could also try a different thermometer. Rutlands can be off by a bit.

 

[maple1]

Seems to be another example of someone being misled by a magnetic temp gauge.

Those things are OK - as long as they are used right, and you know what they are really representing. If they aren't, and someone doesn't (both very possible with a new burner), they can be kind of dangerous. IMO. Kind of double dangerous since a new burner might tend to highly rely on one.

 

[Highbeam]

Worse yet the "safe burn range" of a magnetic meter designed to be used on the stove top will be different from a magnetic meter designed to be on the flue pipe. I suspect that is the root cause of the question.

We all know that a flue surface temp of 250 is the minimum safe temperature but a noncat at 250 stove top is being run cold.

 

[MagdalenaP]

The thermometer should be 18" from the top of the stove. It looks much higher than that.

 

[Kevin Weis]

My single wall flue pipe temp at 18" above stove will read about 210 with a stove top temp around 370. This is measured with an IR gun. So I'd say your stove and reading are about right.

 

[bdl]

Thanks everyone. I learned a lot. This was extremely helpful.