Chimney Temperatures too Low?

[jnalexis]

Hi Everyone!

Been reading the forum for a while but this is my first post so I would just like to start off and say thank you for all the amazing information. It has truly provided a very short learning curve to burning wood and using a wood stove.

So I have searched the forums for days trying to find my specific situation with no luck, so I really hope I’m not reposting a topic but I tried.

I am burning an early 90s (92-93) Hearthstone Phoenix given to me by my father from his house in Vermont we grew up visiting.

When burning I am getting basically conflict between my stove top thermometer (StoneGuard) and my Chinney thermometer(Chimguard), or at least from what I read on here I should be seeing.

Basically when the fire settles down from a reload (which I usually have to crack the door for about 90 seconds to 2 min to get really strong flames) my stove will get cooking HOT (450-500+) but my Chimney temps will barely want to stay above 225-250 degrees.

When I reload I will let it climb back up to around 350-400 and then close the door tight, the stove will keep cooking hotter but chimney temps drop right back down just about 200.

Now burning during the day I will continuously check the chimney outside for smoke and there is usually none to at worst a light whisp of smoke blowing around when I reload but most of my burning is at night after work and all I really have to go off then is my thermometers.


I am burning delivered white oak but everything I put in the stove is split in half before going in the stove and checked with a moisture meter. 95% of what I have put in the stove is between 16-20%. At worst I have put a couple pieces in around 21.5% that I split very small.

Can anyone give me any insight? Is this a problem, should my chimney temp be more relative to my high stove top temps? Or is it all fine as long as the stove box is burning hot with flames?

Thank you!!

 

[begreen]

Just to verify, this is a surface thermometer on single-wall stove pipe, right? If so, the flue gases inside will be approximately double of what is read on the surface. So with a 200-250º reading the flue gases will be in the 400-500º. If there is no smoke you probably are ok, especially if this is an interior chimney. Do a sweep after the first cord has been burned and see how much crude sweeps out. That will also give an indication of how cleanly the stove is burning.

 

[jnalexis]

Yes. Single wall surface thermometer.

 

[Ludlow]

Do you have any kind of fan on the stove or one blowing near it?

 

[begreen]

There is the option of switching to double-wall stove pipe if this is a concern. That will keep the flue gases hotter.

 

[jnalexis]

@Ludlow yes! I have a 10” fan in my foyer blowing towards the stove to bring cold air from upstairs towards the stove (split foyer with open floor plan on both levels). It’s is roughly about 11-12’ from the stove.

I have had in the past a box fan running within 6-8’ of the stove but not currently.

 

[Ludlow]

You will never be able to compare pipe temps with a fan blowing on it. Turn fans off and see where the temp hits. Then you can turn them back on.

 

[jnalexis]

Okay just turned the fan off and I’ll check it again in an hour so?

 

[jnalexis]

Well @Ludlow i believe you hit the nail on the head. It’s been about an hour and a half. Reloaded at about 45min to an hour ago, the air turned back halfway. Stove top is sitting just below 500 degrees and Chimguard is reading between 375 and 400. ‍♂️‍♂️

Man I feel foolish but I’m super happy I posted and figured this out I really appreciate it.

Thank you!

 

[Bad LP]

On my boiler I installed a probe type flue gas thermometer. On start up the lower temps are pretty close but once things get rolling the probe is 100-150 degrees different than the magnetic

 

[Ludlow]

Well @Ludlow i believe you hit the nail on the head. It’s been about an hour and a half. Reloaded at about 45min to an hour ago, the air turned back halfway. Stove top is sitting just below 500 degrees and Chimguard is reading between 375 and 400. ‍♂️‍♂️

Man I feel foolish but I’m super happy I posted and figured this out I really appreciate it.

Thank you!

Do NOT feel foolish. I just happened to have run into that before. I'm not really that smart.
You're welcome!

 

[begreen]

Well @Ludlow i believe you hit the nail on the head. It’s been about an hour and a half. Reloaded at about 45min to an hour ago, the air turned back halfway. Stove top is sitting just below 500 degrees and Chimguard is reading between 375 and 400. ‍♂️‍♂️

Man I feel foolish but I’m super happy I posted and figured this out I really appreciate it.

Thank you!

Try turning down the air another 25% at that stage and see if the flue temps come down a bit more while the stove top temp goes up.

 

[jnalexis]

@begreen headed out to dinner now but when I fill the stove when I get back I’ll start messing with it more.

I’ll post again what I find. Thank you all again!

 

[begreen]

Surface flue temps with a robust secondary burn after the air is closed down should be in the 250-300º range. Once the stove is past the secondary burn stage and in the coaling stage don't worry about the flue temps. All the volatiles have been burned off.

 

[maple1]

Well @Ludlow i believe you hit the nail on the head. It’s been about an hour and a half. Reloaded at about 45min to an hour ago, the air turned back halfway. Stove top is sitting just below 500 degrees and Chimguard is reading between 375 and 400. ‍♂️‍♂️

Man I feel foolish but I’m super happy I posted and figured this out I really appreciate it.

Thank you!

But dont stop using the fan.

 

[Ludlow]

Yea, the fan is fine. Evidence of how much more heat you can realize from using single wall.

 

[jnalexis]

@begreen sorry for the delayed response. But past few days I’ve been using your advice on all my burns and just wow. I don’t even understand how the stove is cooking. The other night I literally had the air pretty much completely closed and stove top was pushing over 550 degrees and flue temps of just under 300. Just putting off a tremendous amount of heat.

 

[bholler]

@begreen sorry for the delayed response. But past few days I’ve been using your advice on all my burns and just wow. I don’t even understand how the stove is cooking. The other night I literally had the air pretty much completely closed and stove top was pushing over 550 degrees and glue temps of just under 300. Just putting off a tremendous amount of heat.

As it should be.

 

[begreen]

@begreen sorry for the delayed response. But past few days I’ve been using your advice on all my burns and just wow. I don’t even understand how the stove is cooking. The other night I literally had the air pretty much completely closed and stove top was pushing over 550 degrees and flue temps of just under 300. Just putting off a tremendous amount of heat.

Glad it is working better for you. It's nice when it all comes together.

 

[jnalexis]

@begreen absolutely! Another question for you guys. I found the original owners manual for the stove. It has a section on monitoring stove top tempatures and says a “monitor stove tempature with a stove top thermometer placed on center stone........thermometer should read approximately 800 degrees on HIGH burn.....”

My StoneGuard starts showing TOO HOT at 500. Obviously I haven’t been taking the Stoneguad as gospel cause I’ve been running up to 550 with the secondary burn. But 800 seems insane. @Ludlow

 

[Woody Stover]

I found the original owners manual for the stove. It has a section on monitoring stove top tempatures and says a “monitor stove tempature with a stove top thermometer placed on center stone........thermometer should read approximately 800 degrees on HIGH burn.....”

I sure wouldn't want to see 800. The manual for my KeySTONE says 700 but I wouldn't want to see that either. I've had it to 600 but not often.

 

[Ludlow]

@jnalexis, Whatever the manual says is probably true. So if that spot on the stove is the hot spot, and it is at 800, that would loosely translate into a 400 single wall surface pipe temp, no? That would be right in the zone on the magnetic gauge range.

 

[begreen]

thermometer should read approximately 800 degrees on HIGH burn.....”

That is really high for a stone stove. I wouldn't push it much past 650F.

@jnalexis, Whatever the manual says is probably true. So if that spot on the stove is the hot spot, and it is at 800, that would loosely translate into a 400 single wall surface pipe temp, no? That would be right in the zone on the magnetic gauge range.

Stove top temps and flue temps, especially surface flue temps, do not necessarily correlate like that. It depends on the stove. For example. Our stove typically runs with a flue temp (probe) about 100º less than the stove top. So if our stove is cruising at 600F the flue temp will be around 500F and if this was single wall pipe with a magnetic thermometer the flue temp would read in the 250-300F range. Conversely some stone stove owners have reported running higher flue temps than stove top. YMMV

 

[Ludlow]

That is really high for a stone stove. I wouldn't push it much past 650F.

Stove top temps and flue temps, especially surface flue temps, do not necessarily correlate like that. It depends on the stove. For example. Our stove typically runs with a flue temp (probe) about 100º less than the stove top. So if our stove is cruising at 600F the flue temp will be around 500F and if this was single wall pipe with a magnetic thermometer the flue temp would read in the 250-300F range. Conversely some stone stove owners have reported running higher flue temps than stove top. YMMV

Well, I did say LOOSELY!