Higher than usual chimney pipe temps, any reason to be concerned?

[DiBurn90]

We installed our first stove six years ago (Regency F2500) and have been using it as our primary heat source since then. Have learned a ton from everyone here over the years, definitely been a great experience so far. Had our first fire of the season tonight and had new situation. Hopefully I'm being a little paranoid but would rather be safe.

Outside temps in the low 50s dropping into the low 40s overnight so I put a small load in the stove to keep the chill off the house. I followed my normal cold start process, some paper to heat the fire box and the draft going, then a small top down, took a little time to really get going leaving the air all the way open, normal for these outside temps with a cold stove.

Temperatures measured with IR gun, ~18" above stove for chimney temps.

Chimney temps had seemed to settle around 350°F with the stove around 300-350°F. I was waiting for the Cat to come up to temperature to try to activate it, normally takes a longer with a small load so I check it approximately every 5 minutes or so. When I checked it the pipe has jumped up to 500-525°F and the stove was up to around 400°F put the Cat in, lowered the air slightly (normal process) and kept a close eye on the chimney temp as normally it stays around 350-400°F maybe pushes to 450/475°F when I'm running it harder, mainly based on recommendation from the installer. Chimney temp kept climbing, as it approached 600°F I closed the air all the way down, kept climbing, went outside to check the chimney, thinking maybe it was a chimney fire, no flames, no embers, no red glow, no roar from the pipe, normal color and amount of smoke. Chimney temp peaked around 675-700°F, held there for a short period, then slowly started to drop back down. Stove never really got much over 400°F.

Whole thing probably didn't last more than 2-3 minutes before it leveled off and started to drop but definitely got my heart rate up a bit.

Once I calmed down a bit I'm thinking this was potentially just the wood off gassing hard and temps spiking from me leaving the air open too long, but the chimney temps being that much higher than normal and the stove temp being that low has me a bit puzzled. Is this something I should be worried about? I know single wall pipe is rated for the temps it saw but could this have been a chimney fire? Appreciate any thoughts/insight anyone can provide.

 

[EbS-P]

the fact that it dropped so quickly makes me not concerned. I’m guessing it was extra dry wood and it all took off at once being a small loosely packed load. If the stove is starting from cold it usually takes more than a couple minutes to see stove top temps change more than 50 degrees.

 

[Woody5506]

What kind of wood ya burning? Only time I've had a chimney fire was when a load of honey locust took off out of no where to the point of flames just shooting up the chimney from the stove. So, not exactly a creosote ignited chimney fire, just a crazy runaway fire I think...if that makes sense. Point being, it sounds like maybe yours did something similar. Sometimes small loads of wood can take off quick.

 

[Slimdusty]

What kind of thermometer are you using? Surface or probe type?

 

[blades]

not that unusual with wood under15%, get a lot of off gassing all at once. compounding this is the none adjustable secondary combustion air intake on most stoves now days. Before the EPA stuck there nose in things most units with seconday air burns had adjustable secondary air controls.

 

[Todd]

I think you need to engage the cat sooner. If you figure your single wall pipe is at 350 external the internal temp is about double that around 700. With those temps 18” up on the pipe your cat should be well over that. I engage my cat when I reach 500-600 internal pipe temp.

 

[begreen]

I think you need to engage the cat sooner. If you figure your single wall pipe is at 350 external the internal temp is about double that around 700. With those temps 18” up on the pipe your cat should be well over that. I engage my cat when I reach 500-600 internal pipe temp.

Agreed. The surface temp on the stove pipe is a lagging indicator. I have found I have so much better control of the fire with a digital probe thermometer providing real-time flue gas temperature.

 

[DiBurn90]

the fact that it dropped so quickly makes me not concerned. I’m guessing it was extra dry wood and it all took off at once being a small loosely packed load. If the stove is starting from cold it usually takes more than a couple minutes to see stove top temps change more than 50 degrees.

That makes sense. It was some old red oak splits mainly that are definitely very dry. The stove temps not changing didn't overly surprise me but thought was worth a note in case it pointed to something else. Thanks.

 

[DiBurn90]

What kind of wood ya burning? Only time I've had a chimney fire was when a load of honey locust took off out of no where to the point of flames just shooting up the chimney from the stove. So, not exactly a creosote ignited chimney fire, just a crazy runaway fire I think...if that makes sense. Point being, it sounds like maybe yours did something similar. Sometimes small loads of wood can take off quick.

Was some old dry red oak mainly with a little maple and ash mixed in. Makes sense. Thanks. Don't do a ton of small loads, normally seem to either be burning or not for some reason last couple years. Could be the little ones and wanting the extra sleep sometimes lol.

 

[DiBurn90]

What kind of thermometer are you using? Surface or probe type?

I have a magnetic surface thermometer on the stove and one on the stack at ~18" but normally use a IR Gun thermometer to take a surface reading when loading the stove too since the others lag a decent amount on startup and a new load. Haven't gone down the rabbit hole of looking into a probe yet but might consider it now.

 

[DiBurn90]

I think you need to engage the cat sooner. If you figure your single wall pipe is at 350 external the internal temp is about double that around 700. With those temps 18” up on the pipe your cat should be well over that. I engage my cat when I reach 500-600 internal pipe temp.

When the stove is warm I normally engage it a sooner, on a cold start it seems like if I do it before it's about 350 on that stack it stalls out more times than not. I think it's due to how the cat sits in the top of the stove when not engaged, almost like it takes longer to get heat soaked and up to temperature. Appreciate the comment for sure, was something I found odd when I got the stove.

 

[DiBurn90]

Agreed. The surface temp on the stove pipe is a lagging indicator. I have found I have so much better control of the fire with a digital probe thermometer providing real-time flue gas temperature.

Sounds like maybe looking at probes would be worth it. I normally don't look at the stove top too much when the stove is warm until after the cat is engaged and everything is going since it lags so much. First cold start I was checking it more than normal. Appreciate the feedback.

 

[DiBurn90]

not that unusual with wood under15%, get a lot of off gassing all at once. compounding this is the none adjustable secondary combustion air intake on most stoves now days. Before the EPA stuck there nose in things most units with seconday air burns had adjustable secondary air controls.

Makes sense guess I have never had it happen on such a small load on a cold start. I think last year was the first year I had very dry wood after putting in effort to get a few years ahead and letting stuff dry, was a big difference in running very dry stuff vs dry stuff under 20%. Thanks

 

[DiBurn90]

Thanks for the feedback everyone, sounds like I was being a bit paranoid, probably a little more concerned since it was the first fire of the season. I'm always a little more concerned on things early season before I get back into the routine. which I was hoping but having feedback from people who know is much appreciated!

 

[blades]

This time of year I don't put much in my stove, It is mostly small cutoffs and odds and ends. small fires to get a bed of coals then some larger stuff to last longer and set off the secondaries. That makes enough heat to keep the place cozy all day.