How warm should double wall pipe get?

[GrumpyDad]

I'm learning how to adapt to my stove's quirks as best as possible and have gotten to the point now that I found that if I leave it around 4th from the highest or 5th, and keep it loaded no more than 1/2 of the way, I can rely on a fairly steady fire.

However reloads are a bit tricky. I find that I have to open the damper, and then set air control to max. I can only put about 4-5 pieces in or else the stove is unmanageable. (wont go into that here). The goal is to run this at 4th from the highest or 5th setting on air control therein. However to get there I have to let that new load 'catch' before switching to secondary (closing the internal damper) and then sometimes I can immediately lower the air control to 4th setting, other times I have to wait another 15 mins because otherwise the load will start to just smolder. That's a bit of babysitting but far better than Ive dealt with so far for fairly consistent 475-550 STT temps.

Recently though, I loaded in what I believe was 3 pieces of oak and 1 cherry, medium but more on the larger side. It wasnt catching after 15 minutes, so I left and came back another 15 and it still wasnt enough for me to shut down to secondary. Another 15 minutes later and the fire box was full of flames, so I quickly shut down to secondary and lowered my air control

But I started to hear stove pipe pings (and a few snap, crackle, pops). My pipe temps were at 300 above the stove about 18", then 325 a bit higher on the telescopic pipe bottom section, then 300 again about chest height. It went down from there until the first elbow, it was 290, then down again until the ceiling box, the outside of the connector was like 250. It just 'feels' scary when it gets to that temp on my IR. Maybe because my last experience with that resulting in a 'creosote burnoff' which sound like small firecrackers going off in first half of the pipe section and smoke puffing out of the pipe joints.

Is there a 'safe' temp to run stove pipe at?

EDIT: If I just shut straight down to secondary, the 4 new pieces will smolder, blacken the glass and of course they smothered/cover the nice bed of coal until they can catch and draw the flames up. This is how I keep my glass clean now and heat consistent.

 

[akgal]

Thanks fir asking this, have wondered myself.

 

[rijim]

First 300 deg F doesn’t worry me depending how it was measured, is this single wall pipe? What kind of stove, and total chimney height do you have?

 

[begreen]

The title says double-wall, but I'm not sure what is being used to measure the temps. It's a VC Dauntless. Based on the description it sounds like running the stove with the air mostly open is making for a hot flue due to the lack of secondary combustion and most of the heat is going up the chimney. A catalyst in the stove should reduce this and make the burn more predictable with lower flue temps. This has been discussed in previous posts.

 

[Eman85]

Just checked my DW 8" stove pipe. Temps measure with IR gun STT 500 Cat 800 DW pipe @2'180* at 4'140* at 6' 130* Stove has been burning constant for a few days now. Load in the stove is down below 1/2 full cat peaked at 1300+ and it's on it's way down.

 

[highanddryinco]

My setup has about 18' of double wall before it gets to the ceiling support box. The "Duravent" labels have turned brown and mostly disappeared up to about the 12' level. Suffice to say, it's been toasty a few times over the years. Safe to assume most of that has been from hot starts before I start to choke things back down.

 

[GrumpyDad]

First 300 deg F doesn’t worry me depending how it was measured, is this single wall pipe? What kind of stove, and total chimney height do you have?

15' and it's double wall.
@begreen the cat doesn't make a difference here as I'm not going through secondary. I'm waiting for fuel to catch at this point. And obviously I missed they it caught when I was away doing other things.

 

[j7art2]

My double wall averages about 125 degrees when my probe flue thermometer is reading in the mid/high orange.

300 on double wall seems awfully warm. Do you have probe flue thermometer? I was all over the place (and was surely overburning) for the first month or two I got my unit. Getting that probe thermometer was a fantastic investment in being able to better operate the stove for me... I'm able to run much cooler than I thought I was actually running.

 

[barnaclebob]

the bottom of my double wall gets really hot. It used to make the wall behind the pipe too hot to touch for more than a couple seconds so I added a pipe heat shield.

 

[GrumpyDad]

the bottom of my double wall gets really hot. It used to make the wall behind the pipe too hot to touch for more than a couple seconds so I added a pipe heat shield.

Wow that's really hot!

I dont really feel radiant heat from my pipe, but I touch it very briefly to check temps followed by IR. I was surprised to see some people saying 150 / 180 with a nice STT temp.
I stopped reading Cat temps, wild swings with no apparent reason just frustrate me further on this stove.
I dont do flue temps internal.
I think STT is important as it determines the heat coming from the stove (the purpose of it). Although a temp wild swing of a high STT does not necessarily mean the overall stove mass is heating high. On startup for example, I can get a STT of 550 and the sides are still cool enough to touch for 10 seconds. STT is for running steady state, and as it changes FIRST - it's a great forecast of things to come (and to avoid over/under burning)

 

[begreen]

15' and it's double wall.
@begreen the cat doesn't make a difference here as I'm not going through secondary. I'm waiting for fuel to catch at this point. And obviously I missed they it caught when I was away doing other things.

Yes, I was referring to the challenging startup. The double-wall temps are high, but that can be expected if the bypass is open for a long time. All the heat is going up the flue. It's best to set a timer if one needs to step away from the stove at startup. It's too darn easy to get distracted.

On our stove, with DVL double-wall, there is an offset at the bottom. The surface temp right now is 210º on the face of the offset elbow, 175º at 21" above the stove, and 130º up near the ceiling support. The internal flue temperature is 585º.

 

[GrumpyDad]

Yes, I was referring to the challenging startup. The double-wall temps are high, but that can be expected if the bypass is open for a long time. All the heat is going up the flue. It's best to set a timer if one needs to step away from the stove at startup. It's too darn easy to get distracted.

On our stove, with DVL double-wall, there is an offset at the bottom. The surface temp right now is 210º on the face of the offset elbow, 175º at 21" above the stove, and 130º up near the ceiling support. The internal flue temperature is 585º.

Wow that's a big difference in temps inside and out. Good idea on the timer. It's easy to get distracted

 

[Crab]

I measure almost exactly the same temps on my DW stovepipe as begreen did at 20" above the stove(170F) when at 600F internal flue temp. I use an Auber digital AT200CHIM. I see it's now 85 bucks shipped. It shows real time internal flue temps. At the least it will at least give you an accurate internal temp and perhaps a little piece of mind on what is going on in the flue. It does for me. . And 2 alarms can be set.

I have a Jotul F45 and can easily see re-burn happening where I don't think you can . Looks like the VC reburn is hidden from sight and you have a bypass. Wow. That makes it tough to judge when to close the bypass to be able to get a good re-burn without snuffing out the fire. Although I can see the flames, I use the Auber to learn what temps I need to start lowering airflow to produce re-burn at start up and after a re-load. I do NOT rely on STT as they lag terribly. So other then piece of mind on flue temps I wonder if an Auber could be used to judge when you should close the bypass for a good re-burn. Just a thought.

 

[highanddryinco]

I must say, as someone who regularly runs quite hot at start-up, I'm enjoying this discussion. Especially the comments from those that have flue thermometers and are comparing their DVL surface temps to the internal flue temps. Makes me realize just how hot I'm likely getting my flue. My DVL surface temps are always between 200F and about 280F, and occasionally higher. At startup, I'm always popping well over 300F and usually up to about 360 for a good 5+ minutes on a DVL pipe surface temp.

I've only ever had a magnetic STT thermometer which reads very consistent with my IR gun. Rarely am I trying to maximize burn times as I've pretty much got an unlimited supply of bone dry pine from the mountain and only a sprinkling of ash from some local dead suburbia street lining trees. Suffice to say, when I burn, I like the heat! Rarely does my stovetop ever get below 500F during a normal burn, more than likely it can be found around that 650F point.

Back to the original point of this thread and looking at my pipe surface temps...you all may have me convinced to throw in an actual flue temp meter of one type or another just because. (FWIW, and on the plus side, my chimney sweeps are quite non-eventful)
As always, I truly appreciate the knowledge shared by the very experienced members on this site.

 

[mdocod]

Measured with a IR gun for surface temps and a FlueGard probe for EGT @18": 6' and 12' are estimated based on extrapolations... The IR gun is only accurate on a 6" wide stive pipe to about 4 feet away. Beyond that the "beamwidth" is too wide and I'm not climbing a ladder up over a hot stove... lol

Measurement Position:	700F EGT DW:	700F EGT SW:
Stove Collar near ECO-FAN	350F	350F
18" Above stove surface	190F	290F
6' Above stove surface	150F	220F
12' Above stove surface	120F	170F