External Temp on Double wall pipe on start up

[MishMouse]

I was just wondering what temps people are getting on there double wall pipe upon start up?

I have been trying to keep my temps below 600, but sometimes when I close the bypass when the pipe gets above 500 it can get up to 700 before it starts to fall.
I am assuming this is due to the AB and the fact that the pipe temps are still going up when I close the bypass.

Problem is on start-up and on loads the fire seems to be pulled up the flue when bypass is open which gets it hot before the stove itself gets up to temp.
This causes the stove to stall since the full combustion is not reached.

I have tried leaving the top load door open until load is somewhat burning and this does seem to keep the temps down on the pipe.
But, after I close the door the pipe temps rise above 500 and the stove top itself is just getting to 300.

My concerns comes from what happened last year when I had to replace some double wall and some class A due to overheating the pipe.
Last year I let the stove top get to 500 before closing the bypass, this had the pipe kept getting above 700 and sometimes even spiking.

Could my issue be that I have to much draft which is causing the flames to be pulled up the flue?
If so is there anything I can do about this?

Thanks...

 

[Todd]

Are you running with the air control wide open in the bypass mode? Less air will keep more of the heat in the stove verses up the pipe.

 

[begreen]

This is the referred thread:
https://www.hearth.com/econtent/index.php/forums/viewthread/72846/

It may be draft, but is it hard to quantify because surface thermometers are not meant for double-wall pipe. This is not a good place to judge when to close the bypass. Do you have another thermometer on the stove top that you use to judge the time to close the bypass? If not, put the current thermometer on the actual stove top, a few inches in front of the flue and use the temperature there to judge when to close the bypass.

As for the draft, can you describe the flue connector and chimney system on the stove in detail?

 

[nate379]

The outside of the stove pipe is getting 600*?? I'd expect that with single wall but no way for a double wall! The would mean the inner pipe is in meltdown mode.

My pipe a few feet above the stove when it's runny full bore is cool enough I can put my hand on it. Maybe 200-250 at the very most.

 

[WES999]

You really can't get a meaningful reading on flue temp with a magnetic thermometer
on the outside of double wall pipe.

FYI
On a cold start with dry a lot of dry kindling, the inside of the pipe can be as much as 1000 °F
while the outside can be as cool as 130 °F , you can put your hand on it with out burning.
Bottom line, you need a probe inside if you want to measure double wall temp.

 

[Highbeam]

Yeah, something is funny about a 600 surface temp on the outside of the outer wall of double wall. Error in measurement.

 

[Diabel]

Yeah, something is funny about a 600 surface temp on the outside of the outer wall of double wall. Error in measurement.

Yup....possibly the thermo is totally gone south..............

 

[MishMouse]

I should have some time over the weekend so I can post pics of the setup.
Until then I tried to create a picture.

1 - Front top Right of Stove
2 - Top of stove center on top loading door around 1-2 inches from door edge.
3 - Around 18 inches from stove top on a 45 angle pipe duravent double wall pipe
4 - Around 26 inches from stove top on a 45 angle pipe duravent double wall pipe

#3 is the one that gets very hot when I am trying to get either #1 or #2 into burn zones.
#4 doesn't get above 400

 

[BrowningBAR]

I'm running a double wall pipe for the Heritage and that stove is known for hot flue temps. That being said, even at 600 degree stove temp the surface of the double wall pipe temp doesn't get anywhere near those temperatures. Usually the range is around 150-250.

One of the main points for using double wall pipe is to reduce clearances. With a surface temp of 400-600 you will have clearance issues. Something is very wrong.

 

[BrowningBAR]

Yeah, something is funny about a 600 surface temp on the outside of the outer wall of double wall. Error in measurement.

Yup....possibly the thermo is totally gone south..............

Let's hope that's the problem.

 

[MishMouse]

A little bit more about the pic.
This shows what is going on when the bypass is open.
When I drop the air all the way down it put the fire out in the front part of he stove, but still at the back the secondary air is still coming in from the rear of the stove, so it is still pushing fire up and out the stove. The problem is it is only heating the back part of the stove and not the entire stove.

I found out if I put the air on low and leave the top load door open I am somewhat able to get the the fire going while keeping #3 under 300, but this doesn't allow for complete combustion until I close the door and of course then the temps at #3 take off.

 

[MishMouse]

Once I close the damper and the heat is sent through the AB, the temp does go by around 100 degrees, then it starts to fall down to normal operating temps < 200.

 

[BrowningBAR]

A little bit more about the pic.
This shows what is going on when the bypass is open.
When I drop the air all the way down it put the fire out in the front part of he stove, but still at the back the secondary air is still coming in from the rear of the stove, so it is still pushing fire up and out the stove. The problem is it is only heating the back part of the stove and not the entire stove.

I found out if I put the air on low and leave the top load door open I am somewhat able to get the the fire going while keeping #3 under 300, but this doesn't allow for complete combustion until I close the door and of course then the temps at #3 take off.

Even with the bypass open those temps are way, way too high. To put it in perspective, those are the temps I get on my vigilant with the bypass door open, and that's single wall pipe.

The 300 degree temp when you have it choked down is too high, as well. Unless I am missing something. Unless you miss-spoke and this isn't double wall pipe?

 

[leeave96]

FWIW, I have a double wall pipe coming horizontally out of my Keystone into the chimney with a magnetic thermometer on the top of it about 12 inches from the stove. I realize this is not an accurate measurement of what's going on, but it is a good indication of when things are getting to hot - learned from experience using the stove and watching for heat vs temps. Sometimes mine will get 400 degrees, but usually (in bypass) it will get close to 300 degrees. At that temperature, the stove top is reading easily 250 degrees and I need to engage the cat. Once the cat is in, the stove top will go up and cruise at 500ish degrees and the stove pipe temp is down to 200-250ish.

Bill

 

[begreen]

We really need to know the stovetop temps. If this is not the thermometer, the bypass is being closed far too late. 600F surface temp on double-wall connector is far to hot and likely far above the pipe's inner liner rating.

 

[MishMouse]

On #2 the stove top it is just getting above 250 when #3 is getting close to 500

 

[begreen]

I's the diagonal run that is heating up. I can take some temp readings off of our double-wall once we start burning more regularly. We have a pair of 45s offset after the flue collar. I'll see what it reads there.

In the meantime I'd experiment trying closing the bypass earlier. What is the lowest temp that you can close the bypass at and still get good afterburner combustion.

 

[MishMouse]

When it is in good AB, the pipe is between 150-200.

 

[BrowningBAR]

Right now the Heritage is cold. When I start it up in an hour or so I'll post my start up temps on my pipe.

 

[Diabel]

I just fired up my encore that also has double wall. I placed
magnetic thermo just above my internal probe thermo which
is 18" above the stove. Right before I was ready to engage
the cat (close bypass) the probe thermo read 550*
the magnetic thermo on double wall read 350*.
Right now 15min later after closing bypass the probe reads
375* the magnetic on double wass reads 200* stove top
550* and the cat probe 600*
I still think your thermo is done. They are very inexpesive!!
And will provide a piece of mind!

 

[BrowningBAR]

I just fired up my encore that also has double wall. I placed
magnetic thermo just above my internal probe thermo which
is 18" above the stove. Right before I was ready to engage
the cat (close bypass) the probe thermo read 550*
the magnetic thermo on double wall read 350*.
Right now 15min later after closing bypass the probe reads
375* the magnetic on double wass reads 200* stove top
550* and the cat probe 600*
I still think your thermo is done. They are very inexpesive!!
And will provide a piece of mind!

Yeah, I just got the Heritage up and running and the highest external temp reading so far is 212°. Stove top is sitting at 300° and climbing. I am 30 minutes into a cold start.

 

[rdust]

If it's really 600* that is WAY to hot for an external double wall temp!

 

[turbocruiser]

Just as added data, on our Regency even when the collar/connector is at 650 to 750 degrees the outside of our Double Wall ( ICC Ultra Black ) is 200 to 250 degrees at hottest area (measured with my IR) so as all the other much more experienced experts here have stated already, something sounds way wrong with the temps the OP posted.

 

[begreen]

I got a similar hottest reading of 225F on the diagonal section of our DVL pipe, while the vertical read 152F. This was with poplar burning and the stove top at 450F.

 

[begreen]

OK, with the flue thermometer on the vertical section of the DVL reading 600F, the surface reading next to it was 225F. The hottest temperature I read on the diagonal surface was 303F or about 50% the flue gas temp. If we extrapolate that to your setup it would mean that with a 600F surface reading on the diagonal of the double-wall, the flue gas temps would be about 1200F.:exclaim: That's too hot!

Try closing the bypass much sooner and see if the afterburner can still combust at much lower pipe temps.