Improved Heritage burn using chimney damper - REVISED: New IR Thermometer - bunch o readings.

[edthedawg]

I tried something new with our new Heritage this morning - choking down the flue damper a little. It's a 6" stainless, uninsulated Z-liner w/ a spring-loaded damper w/ pullchain inside the firebox - the damper "door" is actually way up at the top of the chimney about 40 feet up. I brought it down maybe halfway, maybe a touch more (i'll need binoculars and have to stand in the neighbor's parking lot to see it for sure) It seemed to really help reduce the air movement inside the firebox, which has been ripping strong even with the primary shut nearly all the way off. Remarkable difference in the appearance of the secondary burn - more mature flame, hovering nicely, not really attached to the splits, and also not getting sucked out the top too quickly. Was definitely still drawing well enough - nothing backing up into the room, even 45 minutes later.

I can only imagine this was very inefficient running the flue wide-open - sending way too much heat up the chimney and keeping not nearly enough inside the room, even w/ the primary shut off. Reading here indicated the primary SHOULD be enough to control the burn, but I really think the draft from this chimney was just pulling a ton on me...

This may be the critical operating parameter I was looking for to go over 400F (still waiting for my damned IR thermometer to show up). We got a good 7 hour burn last night - coals from 4 or 5 smallish splits were plenty hot to rekindle this morning, but it'll be very interesting to see if we can extend the burn even better now.

I had only originally intended for this damper to be a simple shutoff to keep birds, squirrels, bats, snow, sleet, and rain out and reduce any heat loss up the flue - but I can't imagine this is the wrong way to use it - right?? It shouldn't matter that the damper is on the top of the flue vs. right down next to the tee - right?? :cheese:

Curious if anyone else is using such a method / damper, and if I can expect to have to continually open it up and close it down, maybe only when it's a total cold start, etc. Hopefully I can not have to stick my hand behind the stove too much on a daily basis...

Thanks all for the helpful advice here!

 

[Highbeam]

Your Heritage manual discusses the need for a flue damper. It is based on the actual amount of vacuum "power" of the chimney and I have got to imagine that with 40 feet you would have met the criteria. That's a lot of chimney over the minimum required 13 or 14 feet and longer chimneys suck much harder than the design chimney.

The beauty of your top mounted damper is that it won't get in the way for cleaning.

 

[edthedawg]

I know I'm not climbing up there to do the cleaning!

 

[struggle]

I have long been a fan of the inline dampener since I installed the Mansfield 2 1/2 seasons ago. It helps greatly with fine tuning these stoves.

If you do not have a probe thermometer I strongly recommend that as well since then you will see first hand how much heat is going up the chimney and you will be able to dial in the stack temp for clean a clean liner and still get the most out of your wood in burn times.

You might be better off using a dampener just above the stove if possible rather then having to go outside to check position. I also would be worried about the dampener up top closing on its own if that is possible in higher winds.

 

[edthedawg]

The spring tension is pretty fierce - I have to give it a good yank to pull it down - so not worried about the wind any more than if left wide open w/ the chain hanging. What I will do however, is to verify positioning and then put a bright orange alignment mark on the chain and the firebox sidewall so I can be sure to always put it in an "optimal" location.

 

[_CY_]

don't have a heritage, but do use damper to control how fast smoke goes up the chimney.
slower exhaust means longer contact with heat exchanger. but it also means possibility of carbon monoxide backing into your living area.

be really careful making adjustments. be dead certain smoke doesn't come out when door is open.
do this with a carbon monoxide detector close by. which everyone should have operating a wood stove anyways.

once damper is set... I'll leave alone for the season.

Curious if anyone else is using such a method / damper, and if I can expect to have to continually open it up and close it down, maybe only when it's a total cold start, etc. Hopefully I can not have to stick my hand behind the stove too much on a daily basis...

Thanks all for the helpful advice here!

 

[larryhollenb]

I haven't seen many stoves that don't spill smoke when filling if they have any size opening door. I have had new stoves and old stoves and only a couple were fairly free of that aggravation. I have a very large feed door on an older stove now who's flue exit area is rather small and almost anytime I open the door with a slow or recently started fire I get smoke spill on loading. I have a tall chimney so one would think the draw would be sufficient but it isn't.

As too an inline damper, I have always thought that a stove pipe damper was a help in controlling a fire as well as increasing the heat output. Some disagree, but I have used cookstoves and others for years and when you turn the damper some to hold the heat, you can at once feel the heat coming up from the cooktop which means to me its holding the heat better than just going up the chimney too quickly.

 

[edthedawg]

Well last night the fire was good enough to relight from the morning's coals, but quickly went right out. several times. with wood that had been indoors for a few days sitting near the stove. While moisture in the wood certainly factored in to some extent, we found it was just being stubborn until we reopened the damper all the way and let it build that way. then we pulled it down a couple notches and got a nice steady, 400F+ burn going. Same thing this morning - good coals, fire started right up on a couple kindling sticks and 3 splits, but was stubborn about staying up and building until i opened the damper all the way.

Perhaps I can rig myself a little ratcheting turnwheel for the cable up to the chimney cap, instead of dealing with the finicky chainstop. in the dark. behind the stove. every time. *grumble* :vampire:

 

[_CY_]

hmmm..... don't like the idea that if door gasket leaks... carbon monoxide will spill into house...
that's why when adjusting my damper... will only slow down smoke to just above door threshold.

CO meter sits right above door opening... then I'll use a Fluke CO meter to double check that.
can't be too careful about CO getting into your living area.

I haven't seen many stoves that don't spill smoke when filling if they have any size opening door. I have had new stoves and old stoves and only a couple were fairly free of that aggravation. I have a very large feed door on an older stove now who's flue exit area is rather small and almost anytime I open the door with a slow or recently started fire I get smoke spill on loading. I have a tall chimney so one would think the draw would be sufficient but it isn't.

As too an inline damper, I have always thought that a stove pipe damper was a help in controlling a fire as well as increasing the heat output. Some disagree, but I have used cookstoves and others for years and when you turn the damper some to hold the heat, you can at once feel the heat coming up from the cooktop which means to me its holding the heat better than just going up the chimney too quickly.

 

[Highbeam]

I was under the impression that these flue dampers were always to be opened anytime you open the door or start a new fire. I expected to be turning that thing all the time. You guys really set and forget?

 

[edthedawg]

OK I decided to keep this in the thread as opposed to creating yet another new one - we can split it out or edit the title or whatever is appropriate.

I got the IR thermometer today and of course I've been measuring everything I can point it at, plus trying all kinds of stuff w/ the stove. We're heading to overnight now so i deliberately put a too-large split in on top of a huge, hot coal bed. Prior to that I had 3 or 4 smaller splits roaring - great looking fire, and it "felt hot" regardless of the damper and primary settings. Damper is now pulled nearly shut, and primary is working its way down. Getting some good secondaries but not as much as I'd like - again the large, wettish wood is overwhelmingly likely culprit here. So this isn't a rant/whine about why I can't get to 500F on the stovetop - I'm pretty content in knowing what I need to do - smaller, dryer splits. More of them, and a cup of patience to go with it. I was outside a couple times tonight and didn't see any smoke from the chimney, but it was admittedly quite dark.

What I am curious about are a couple of the IR readings.

Hottest spots:
- The glass door (600+: I assume it's reading thru the glass onto the coal bed)
- The cast square around the top center block-off plate - the enamel gets to about 460F, and drops off sharply anywhere 1/2" away either onto the steel circle (<300) or onto the neighboring stones, which quickly drop to about 325, and then drop as ou move outward smoothly down to about 260. Center of the front, center stone is about 300 - the Rutland is spot-on. Leak around the block-off plate? or is that hotspot around it normal and ignorable?
- The side load door stone got up over 400 a few times - not worried.
- The flue exit pipe and tee seemed very happy around 220-280. When I had the damper and primary both more open, I had the flue up around 330-350, and heard what sounded like a subtle boiling sound. Creosote coming out? Boiling? Forming? It was a new noise for me.
- Hearth tiles under stove were 100-120
- Underside of mantle: 170. That one concerns me. We're going to have to put in that heat shield.

All comments appreciated - thanks!

 

[edthedawg]

*bump* - just curious for thoughts from the just-waking-up crowd

 

[SaratogaJJ]

What I am curious about are a couple of the IR readings.

Hottest spots:
- The glass door (600+: I assume it's reading thru the glass onto the coal bed)

All comments appreciated - thanks!

I'm curious about this myself...does an IR thermometer pointed at the glass door (actually, it's ceramic, and that might be an important distinction) register the temperature of the ceramic itself, or the temp of what is going in behind it? I measured the temp of my Hearthstone Morgan door at about 650F last night, and ended up throttling back the air intake completely closed for about an hour to bring it back down to the mid-500's. Did I do the right thing? The leading edge of the top surface I measured at about 300F at the same time...which measurement is more important?

 

[edthedawg]

I got the exact same readings - 600+ in the "glass" but laser spot essentially on the coals. slide the spot up to the metal stone above the door, and it was in the 300's. I think that's just the temp of the coals - you probably didn't need to throttle it back - stovetop temp and pipe temp are the two most critical temps, AFAIK.

 

[relax]

ok here we go again,i ve been playing with putting a putty knife in front of my air intake ,covering maybe 3/4 of the opening ,doing this only after i gotter in cruse mode and good secondaries,,,*Im getting a very nice slow burn,NOW i would like to know is it best to install a damper or to magiever a air restricter at the air intake...this was covered in a past thread but got no real answer....I do not know wich waay to go...please chime in...asap

 

[edthedawg]

I'm far from an expert, but it seems to me that if you want to keep your secondaries, then choking off their air supply is a suboptimal idea.

 

[relax]

my secondaries seem to do fine,looking at slowing the burn rate down a little more than my control lever will allow,maybe ill look into installing a damper above my stove...

 

[edthedawg]

Ah - Seems like not a bad idea. I'm thinking of doing the same kind of restrictor on the inlet when i plumb in the outside air feed.

 

[bokehman]

The glass door (600+: I assume it's reading thru the glass onto the coal bed)

No. Open the door 90 degrees and read the temperature off the glass again. You will find it to be more or less the same. The coal bed, if the coals are giving off any visible light, is hotter than 1500 degrees.

I can't get to 500F on the stovetop - I'm pretty content in knowing what I need to do - smaller, dryer splits.

If your wood seasoning is suspect that's going to hurt your temperature and burn time quite a bit, but, 500F is pretty hot for a stone stove according to what I've read on here.

The flue exit pipe and tee seemed very happy around 220-280. When I had the damper and primary both more open, I had the flue up around 330-350, and heard what sounded like a subtle boiling sound. Creosote coming out? Boiling? Forming? It was a new noise for me.

To me that sounds like the point where you are just starting to make some draft. With my setup with the primary right open I get a strong sub-bass rumble.

Getting some good secondaries but not as much as I'd like - again the large, wettish wood is overwhelmingly likely culprit here.

If you must use a flue damper you should have some sort of depression meter. Start the stove with the damper right open and once the chimney is up to temperature limit the draft until you get the correct stack depression. I would consider adding a limiter so the damper cannot be closed further than this point.

 

[kenny chaos]

[quote author. With my setup with the primary right open I get a strong sub-bass rumble.
.[/quote]

I like sub-bass rumble. Kinda like something Max Roach does.

 

[edthedawg]

No it wasn't bassy at all, and i haven't replicated it - had it ripping hot last night so didn't need to fire it up high before bed, despite it being 28F out when we woke up. House was still mid-60's everywhere. I love this IR thermometer tho - and very glad I followed the recommendations for the hearth coverage and R-value - I regularly measure 150-170F on the tile floor about a foot from the stove!

 

[Todd]

I got the exact same readings - 600+ in the "glass" but laser spot essentially on the coals. slide the spot up to the metal stone above the door, and it was in the 300's. I think that's just the temp of the coals - you probably didn't need to throttle it back - stovetop temp and pipe temp are the two most critical temps, AFAIK.

The temps inside a non cat stove need to reach 1100 degrees in order to burn the secondary gases so the 600 temp is prolly the glass. You can take a blow torch to ceramic glass with no ill effects. You right, monitor the top center stone and pipe temps for stove ops.

 

[edthedawg]

It's down to about 26F out, and still falling a few more tonight i think - we've had the fire going all afternoon/evening/night and it's deliriously warm everywhere in our 2800 sq ft Vic. Loving the wood! I only heard the boiler run when someone took a shower or did laundry. If the stovetop keeps hovering around 300-350 and we're plenty warm enough, I'm gonna kinda be ok with that.

 

[velvetfoot]

I had been burning up some hemlock I had, but it snowed and I burned some hard wood I had in the garage.
At lot more potent, for sure, as seen by the IR.
I have some big pieces in there now for the night, all choked down, nice rolling secondary burn, fan at 1/2 speed: 937F glass.

 

[bokehman]

937F glass.

How much difference do you get between the centre of the window and the corners?