Running the new Mansfield 8013

[mdocod]

Mod Edit: Discussion moved to new thread

Mansfield II 8012 model had a measured emissions rate of 2.8g/h and 68% HHV efficiency
Mansfield III 8013 model with the Hybrid combustion measures 0.54g/h and 78% HHV efficiency

When wood gases and oxygen are burned in a cat, that is an exothermic reaction. Your statement implies that hearthstone has found a way to operate a cat in a manner that burns off combustible gases without generating any additional heat. Not only does that not make any sense, the numbers prove otherwise. This stove design benefits significantly from the addition of the cats. The amount of combustion that takes place in the cats on this stove, when operated "normally" (at recommended settings) is a lot less than in a dedicated cat-stove, but it was enough to take this stove from 20 years ago ordinary to one of the most efficient and clean burning stoves on the market.

In my experience, when the Mansfield "Tru"Hyrbid (marketing wank) stove is choked way down, the secondary combustion will shut-down after 2-3 hours slow-flaming, but the wood is still fairly rich with wood gases, at that point a point fuel that would have gone up the chimney unburnt begins to burn exclusively in the cats. The cats start going tink tink tink and the temperate probe over the cat shoots up higher, causing the soapstone's and cast pieces up near the back corner of the stove to heat up (confirmed with IR gun), and also causing the EGTs to go higher, which is part of why I believe this stove works better with some single wall above it. When the cats are really cooking right below the exhaust collar its good to have a way to extract a bit more of that heat into the room to take advantage of that "phase" of combustion on these stoves.

With that said, the Mansfield is not well optimized to operate like a wood gasifier/cat-combustor the way the BK/Woodstock stoves are. The cats in this design are just sorta sitting there on a plate, they don't have a good way to conduct heat into the surrounding materials, so it's mostly radiated heat and higher EGT's up for grabs there. It doesn't perform as well when operated this way and that method of operation is discouraged in the manual. I've played with it on a few cycles, and yea, the cats will light off and get super hot but it's not as clean or efficient running this way as it is with active secondaries. The cats on this are not as fine a mesh as found on other systems, and the catalyst material chosen is something simpler/cheaper (supposed to be lifetime cats). It works best when operated with the air intake about 1/4-3/8" open as indicated in the manual, which results in steady secondary combustion lasting through almost all of the wood-gas release phase of the burn. When operated this way the cat just picks up the slack that secondary combustion misses both during active secondaries and for awhile after flames drop-out in the firebox. At these settings the stove can deliver slightly slower burn rates, slightly cleaner emissions, slightly longer burn cycles, and slightly better thermal efficiency than you'll get from a non-cat stove. If the cat was "only cleaning up the exhaust" then it wouldn't have gained 10% efficiency with them added (actually from 68% to 78% represents a 15% "improvement"). Combine that with the greater thermal mass and it all adds up to a more drawn-out heating cycle that is more usable and comfortable for most milder days of the year and fringe season heating. I can get 8-12 hours burn cycles on Ponderosa with 9% moisture. There are plenty of people burning hardwoods in non-cat stoves with similar burn cycles so I think the cat is more useful in this application than just cleaner exhaust.

 

[bholler]

Mansfield II 8012 model had a measured emissions rate of 2.8g/h and 68% HHV efficiency
Mansfield III 8013 model with the Hybrid combustion measures 0.54g/h and 78% HHV efficiency

When wood gases and oxygen are burned in a cat, that is an exothermic reaction. Your statement implies that hearthstone has found a way to operate a cat in a manner that burns off combustible gases without generating any additional heat. Not only does that not make any sense, the numbers prove otherwise. This stove design benefits significantly from the addition of the cats. The amount of combustion that takes place in the cats on this stove, when operated "normally" (at recommended settings) is a lot less than in a dedicated cat-stove, but it was enough to take this stove from 20 years ago ordinary to one of the most efficient and clean burning stoves on the market.

In my experience, when the Mansfield "Tru"Hyrbid (marketing wank) stove is choked way down, the secondary combustion will shut-down after 2-3 hours slow-flaming, but the wood is still fairly rich with wood gases, at that point a point fuel that would have gone up the chimney unburnt begins to burn exclusively in the cats. The cats start going tink tink tink and the temperate probe over the cat shoots up higher, causing the soapstone's and cast pieces up near the back corner of the stove to heat up (confirmed with IR gun), and also causing the EGTs to go higher, which is part of why I believe this stove works better with some single wall above it. When the cats are really cooking right below the exhaust collar its good to have a way to extract a bit more of that heat into the room to take advantage of that "phase" of combustion on these stoves.

With that said, the Mansfield is not well optimized to operate like a wood gasifier/cat-combustor the way the BK/Woodstock stoves are. The cats in this design are just sorta sitting there on a plate, they don't have a good way to conduct heat into the surrounding materials, so it's mostly radiated heat and higher EGT's up for grabs there. It doesn't perform as well when operated this way and that method of operation is discouraged in the manual. I've played with it on a few cycles, and yea, the cats will light off and get super hot but it's not as clean or efficient running this way as it is with active secondaries. The cats on this are not as fine a mesh as found on other systems, and the catalyst material chosen is something simpler/cheaper (supposed to be lifetime cats). It works best when operated with the air intake about 1/4-3/8" open as indicated in the manual, which results in steady secondary combustion lasting through almost all of the wood-gas release phase of the burn. When operated this way the cat just picks up the slack that secondary combustion misses both during active secondaries and for awhile after flames drop-out in the firebox. At these settings the stove can deliver slightly slower burn rates, slightly cleaner emissions, slightly longer burn cycles, and slightly better thermal efficiency than you'll get from a non-cat stove. If the cat was "only cleaning up the exhaust" then it wouldn't have gained 10% efficiency with them added. Combine that with the greater thermal mass and it all adds up to a more drawn-out heating cycle that is more usable and comfortable for most milder days of the year and fringe season heating. I can get 8-12 hours burn cycles on Ponderosa with 9% moisture. There are plenty of people burning hardwoods in non-cat stoves with similar burn cycles so I think the cat is more useful in this application than just cleaner exhaust.

So basically you told him he was wrong you stove doesnt just use the cat to clean up emissions. But the said the cat really isn't optimized to add heat to the home??? You do see the problem there don't you?

 

[mdocod]

So basically you told him he was wrong you stove doesnt just use the cat to clean up emissions. But the said the cat really isn't optimized to add heat to the home??? You do see the problem there don't you?

The stove isn't optimized to operate as a wood gasifier, it doesn't have enough heat sinking on the cats to handle all of the combustion from the stove well, however it clearly improves the overall efficiency of this stove when operated as intended, as a hybrid. If you want to try to squeeze a contradiction out of what was said to score points in the "who can be the bigger internet troll" category be my guest.

You're quite feisty for a forum moderator/staff. It's usually folks with your attitude that are getting booted from forums, not the ones managing them. It's refreshing actually.

 

[webby3650]

The stove isn't optimized to operate as a wood gasifier, it doesn't have enough heat sinking on the cats to handle all of the combustion from the stove well, however it clearly improves the overall efficiency of this stove when operated as intended, as a hybrid. If you want to try to squeeze a contradiction out of what was said to score points in the "who can be the bigger internet troll" category be my guest.

You're quite feisty for a forum moderator/staff. It's usually folks with your attitude that are getting booted from forums, not the ones managing them. It's refreshing actually.

Sorry to offend you by saying what you said more eloquently. Those EPA numbers are nothing the end user will ever see and will barely benefit from. I’m fine with making the exhaust cleaner, why not design it in a way that is of benefit though to the consumer? Is the Mansfield your first epa stove?

 

[mdocod]

Sorry to offend you by saying what you said more eloquently. Those EPA numbers are nothing the end user will ever see and will barely benefit from. I’m fine with making the exhaust cleaner, why not design it in a way that is of benefit though to the consumer? Is the Mansfield your first epa stove?

I'm not offended by what you said, I'm just pointing out that there's measurements that prove what you said to be false.

The design does benefit the consumer. A 15% improvement in thermal efficiency puts it among the highest efficiency stoves on the market when operated as intended (with active primary, secondary, and tertiary combustion). What benefit would it have to achieve for you to consider the new design to be a benefit to the consumer?

The Mansfield is my second EPA stove and probably one of 4 or 5 different EPA stoves that I have operated at some point over the last decade. (obviously some of those would have been EPA to a prior emissions standard).

 

[begreen]

The model 8013 Mansfield is still quite new so we don't have a long-term field record of how it works out for the average user. I'm hoping it proves to be a good improvement over the life of the stove. Though I am not a fan of fragile baffle boards, I like that the baffle boards are more serviceable now. The combustion efficiency has been notably improved. Being a cat stove, this will decline over time with the age of the cat and worse if the cat is not maintained. Given that one needs to remove the fragile baffle boards I wonder how frequently people will be cleaning the cat. The heating efficiency does not appear to have been improved as much perhaps as it could have, but it looks like they have done a better job with the Mansfield than some of the other ponies in the Hearthstone stable. It's a good looker and I hope it does well.

I wouldn't recommend single-wall connector for this stove due to the potential of long burning hours on low and the corresponding low flue temps. From the docs, it looks like the rear flue plate is used to access the cat when top-vented. What is involved when changing the catalyst if the stove is rear-vented?

 

[BKVP]

Correct.

To the OP, read the manual. Operate the stove as prescribed in the manual for the sake of emissions, efficiency, output, and preventing stove damage. The dealer quite often has no clue what he is talking about but may be more interested in making a sale to a customer that appears worried about cat failure leaving him without a stove. He's telling you what he thinks you need to hear to make the sale.

We are lucky enough to have some professional stove people on this site, some dealers, some manufacturers, and some servicemen that are smart and honest.

I only remember one stove, a VC, that actually directed the operator to choose to use the catalyst or not. It was in the manual.

And that stove was certified to EPA compliance with both configurations.

 

[mdocod]

The model 8013 Mansfield is still quite new so we don't have a long-term field record of how it works out for the average user. I'm hoping it proves to be a good improvement over the life of the stove. Though I am not a fan of fragile baffle boards, I like that the baffle boards are more serviceable now. The combustion efficiency has been notably improved. Being a cat stove, this will decline over time with the age of the cat and worse if the cat is not maintained. Given that one needs to remove the fragile baffle boards I wonder how frequently people will be cleaning the cat. The heating efficiency doe not appear to have been improved as much perhaps as it could have, but it looks like they have done a better job with the Mansfield than some of the other ponies in the Hearthstone stable. It's a good looker and I hope it does well.

I wouldn't recommend single-wall connector for this stove due to the potential of long burning hours on low and the corresponding low flue temps. From the docs it looks like the rear flue plate is used to access the cat when top-vented. What is involved when changing the catalyst if the stove is rear-vented?

I expect the long-term of the new Mansfields to be a mixed bag just like the history of other Hearthstone stoves. I have no doubt these will have more "issues" than the average stove as they have a ton of pieces/parts that are held together with cement and gaskets and goop and stuff. There will be cracked stones here and there, and probably other unforeseen tragedy. Cats on these are supposed to be a new longer lasting design, and technically we're not working them as hard in this application so maybe they will last longer than average.

Honestly the fragile baffle board design in this stove is less annoying than a bunch of tubes hanging down below the baffle board in most stoves. The baffles seem sturdy to me, and are very easy to remove and reinstall. There's a simple metal support hanger on the front that acts as a bash-plate protection while loading the box (like a skid plate!) that comes out by lifting one side up, slipping off the retainer, then tilt down and slide off the other side. The baffles are suspended on a shelf that extends around the remaining 3 sides of the firebox and hold themselves in place without the retainer for easy removal and reinstallation.

There's no need to remove the baffles to service the cats, but if we do go in this way it's quick and easy and there's no combustion tubes in the way. For some installations that might be the best option. In my case I just lift up the telescoping section of the stove pipe, stick a piece of wood with slits in it in place to hold it up, then reach down and lift each cat "brick" out through the flue. They can be removed, cleaned, and reinstalled from the flue in about 5 minutes or less.

The manual does indicate that the cats can be accessed through the rear flue plate. I have tried and failed. I can't come up with a way to rotate them from that position to get them to come out from there. If the stove were rear vented we could replace the cats either by reaching up from inside the box with the baffles removed, or reach down through the top-flue instead, (presumably, it would have the cover plate installed on top instead).

If the stove had a way to extract more heat from the cats into the stove body, then it would have lower EGT's, which is something you seem to be concerned about with the advise to go double wall on these. The current configuration, is apt to produce higher EGT's, which would seem well suited to drive single wall effectively. By leaving those last few percetage points of efficiancy on the table they may actually be "tuning" the stove to be more broadly compatible. More on this in a moment...

I was just browsing through a whole bunch of forum posts through the brand specific part of the forum and it's just an endless series of stoves installed with double wall that are over-firing. Like, there must be hundreds of examples of this on the forum. Are we really certain that all these installations should be double wall? I understand that for install clearances to combustibles it is sometimes required, but I suspect a lot of these stoves are being installed with double wall just because that's the general consensus recommendation on here. Seems like there's a theme developing. Double wall = over-fire. The dampers only seem to help if modified, and are a source of smoking up rooms when operators forget to open them when the stove door is opened.

What if there were a system, that would produce greater and greater draft correction factor the higher the temps in the system went? Kinda like a passive but automated process for applying more brakes as the temps go up...

As it turns out, the EPA test configuration with stoves, If I understood the diagrams correctly, has about 8 foot of single wall and 8 foot of insulated class A pipe above the stove for testing. That's the "standard" that stoves are being tuned for, and then out here in the real world we're putting double wall almost everywhere as the default. In doing so we're guaranteeing that we're going to get a lower thermal efficiency from the system than the test configuration would have, all out of concern for keeping a clean chimney in an era where stoves are burning with 10-100X lower emissions than they did just 30-40 years ago and maintaining higher EGT's through the burn cycle since so many more of those emissions are being converted to thermal energy. I'm sorry but this itch to double wall everything is just sounding more and more bogus the more I contemplate it.

My chimney system is cleaner with single wall than with double wall because it can be driven at the temperate the stove wants to operate at with a full load of wood without snowballing, and with the knowledge there's more heat being dissipated into the house I'm fine with running those higher EGT's. If I had double wall with a damper I'd be inclined to choke down the stove to stay under 600F EGT most of the time to waste less heat. The lower burn rates required to do that, combined with the lower EGT's, would almost certainly produce as many or more deposits on the chimney system. The system seems like it was tuned for single wall, and double wall creates problems that have to be corrected with stove mods and pipe dampers.

I live at 7400' elevation, my total chimney height it about 21' which should be just about right without a damper if this system was tuned for sea-level with a 16' damper-less pipe. The "extra" 5 feet (~63%) compared to the EPA test config is on the single wall side and is being driven by a stove that is about 63% larger than the smallest in this range of stoves with similar operating characteristics. Working great this way so far!

 

[begreen]

I was just browsing through a whole bunch of forum posts through the brand specific part of the forum and it's just an endless series of stoves installed with double wall that are over-firing.

It's important to understand that the reason most people first post on hearth.com is that they have a problem. What we don't see are the thousands of people that are not having issues.

It's pretty rare to see a posting here for a cat stove that is overfiring. That may change with the hybrids, but a cat stove is better with double-wall stove pipe due to the lower flue temps when run low and slow. It sounds like the Mansfield is capable of this. If you are running the stove in spring with outdoor temps in the 40-50º range then the flue may see more creosote accumulation, or maybe not. Like I said, this is a new model. The other factor is the exposure of the chimney system. A straight up through the house system is going to stay warmer and cleaner than one that is exterior with tens of feet exposed to cold weather.

Note that a lot of people that post are novice burners, especially this year. Many don't know how to operate the stove correctly yet and are afraid of a brisk fire. That is different from an actual overfire. Mostly the hot fire is caused by the operator not turning down the air soon enough and loading it improperly. Sorting all through that, once the user learns how to load and run the stove correctly, the overfire issues are a small fraction of postings here.

I look forward to hearing more about the stove. The high EGT surprised me. Our non-cat stove usually runs about 600-650º with no damper and double-wall stove pipe. Though when I need more heat it will get up to 700º for an hour or so if pushed.

 

[bholler]

I was just browsing through a whole bunch of forum posts through the brand specific part of the forum and it's just an endless series of stoves installed with double wall that are over-firing. Like, there must be hundreds of examples of this on the forum. Are we really certain that all these installations should be double wall? I understand that for install clearances to combustibles it is sometimes required, but I suspect a lot of these stoves are being installed with double wall just because that's the general consensus recommendation on here. Seems like there's a theme developing. Double wall = over-fire. The dampers only seem to help if modified, and are a source of smoking up rooms when operators forget to open them when the stove door is opened.

That absolutely is not the reality of what happens in the field. Stove over fire either because of excessive draft or user error not double wall pipe. Yes the increased flue temps from double wall pipe will increase draft by a few percentage points but really not enough to make a difference

 

[bholler]

As it turns out, the EPA test configuration with stoves, If I understood the diagrams correctly, has about 8 foot of single wall and 8 foot of insulated class A pipe above the stove for testing. That's the "standard" that stoves are being tuned for, and then out here in the real world we're putting double wall almost everywhere as the default. In doing so we're guaranteeing that we're going to get a lower thermal efficiency from the system than the test configuration would have, all out of concern for keeping a clean chimney in an era where stoves are burning with 10-100X lower emissions than they did just 30-40 years ago and maintaining higher EGT's through the burn cycle since so many more of those emissions are being converted to thermal energy. I'm sorry but this itch to double wall everything is just sounding more and more bogus the more I contemplate it.

Testing is generally done with an exhaust fan pulling the draft specified by the manufacturer. This is so they can test consistently every time. And why it's important to install stoves in a way that is as close as possible to that draft specification.

 

[begreen]

Testing is generally done with an exhaust fan pulling the draft specified by the manufacturer. This is so they can taste consistently every time. And why it's important to install stoves in a way that is as close as possible to that draft specification.

Yes, and frequently these tests are done at whatever the outdoor temp is that month. I often see these test reports with an outdoor temp of 75+º.

 

[BKVP]

I read in this thread an observation of "lifetime cats". Let's breakdown the structure of the unit.
1) You have a substrate, generally mullite or cordierite and in the past 5 years, metallic.
2) Frame Support generally stainless on ceramic combustors
3) Gasketing (both around the cell block of the substrate and the outside of the frame support)
4) Wash Coat-The mix of precious metals applied to the substrate

The threshold temperature for ALL wash coats is 1600F. Repeated exposure to 1600 or higher temperatures will result in the flattening of the wash coat. Visualize an English muffin texture being flattened. This reduces surface area and turbulence as gasses pass through the cells of the combustor. After repeated exposure, over plating takes place. This diminishes make contact of the gasses with the catalyst itself result in reduced efficacy. This is why the cleansing of the combustor with an acidic wash will reduce the amount of over plating but never restore it to 100% efficacy.

Regardless of the substrate, it is the decline of the wash coat that in not subject to interpretation, or marketing hype, although some may try.

Thermal shock can in fact compromise the substrates, more so ceramic, but also metallic. As combustors heat up, there is expansion and contraction of ALL substrate materials. The frame support and gasketing allows for this to transpire with minimal consequence. Air leaks, ice laden fuel or excessively wet fuel also cause such dramatic temperature fluctuations as to have significant impact of substrate integrity. The net result is distortion in metallic substrates and crumbling in ceramic substrates.

Hybrid technology is not new. Blaze King's Princess 1001 was a hybrid wood stove in 1982-83. There were both combustor and secondary tubes utilized in the design. It should be noted the incredible impact the introduction of room air into the firebox can have on the substrate. Secondary air must have sufficient residence time and exposure to firebox temperatures prior to firebox introduction, lest there be additional thermal shock.

Flame impingement can also have consequences to the lifespan of a combustor. Our company had horizontal combustor integration back from 1983-1988. There were hundreds (yes hundreds) of companies making combustor added stoves in the 1980's due to Oregon emission standards. Generally accepted, manufacturers added combustor to existing models with no understanding of long term exposures to solid fuel combustion. They were placed in the flue path, hung below the underside of the top stove surface and anywhere else a 5.66" metal ring could be placed.

Thankfully, a few companies stuck to their guns and kept refining the integration of catalytic combustors to wood stoves. Today's catalytic models are generally much improved than those of the 1980's.

I could have been more concise, but that's not my nature.....There is no "lifetime cat". With that said, once the wash coat thresholds are addressed, Katie bar the door!

BKVP

 

[BKVP]

Testing is generally done with an exhaust fan pulling the draft specified by the manufacturer. This is so they can test consistently every time. And why it's important to install stoves in a way that is as close as possible to that draft specification.

Correct. And the effect of that fan is variable to address draft. Not a single wood stove is tested in a manner in which a consumer has it installed. Even those tested on cord wood are still tested on dilution tunnels!

BKVP

 

[bholler]

Correct. And the effect of that fan is variable to address draft. Not a single wood stove is tested in a manner in which a consumer has it installed. Even those tested on cord wood are still tested on dilution tunnels!

BKVP

Thankyou for confirming that for us

 

[BKVP]

I expect the long-term of the new Mansfields to be a mixed bag just like the history of other Hearthstone stoves. I have no doubt these will have more "issues" than the average stove as they have a ton of pieces/parts that are held together with cement and gaskets and goop and stuff. There will be cracked stones here and there, and probably other unforeseen tragedy. Cats on these are supposed to be a new longer lasting design, and technically we're not working them as hard in this application so maybe they will last longer than average.

Honestly the fragile baffle board design in this stove is less annoying than a bunch of tubes hanging down below the baffle board in most stoves. The baffles seem sturdy to me, and are very easy to remove and reinstall. There's a simple metal support hanger on the front that acts as a bash-plate protection while loading the box (like a skid plate!) that comes out by lifting one side up, slipping off the retainer, then tilt down and slide off the other side. The baffles are suspended on a shelf that extends around the remaining 3 sides of the firebox and hold themselves in place without the retainer for easy removal and reinstallation.

There's no need to remove the baffles to service the cats, but if we do go in this way it's quick and easy and there's no combustion tubes in the way. For some installations that might be the best option. In my case I just lift up the telescoping section of the stove pipe, stick a piece of wood with slits in it in place to hold it up, then reach down and lift each cat "brick" out through the flue. They can be removed, cleaned, and reinstalled from the flue in about 5 minutes or less.

The manual does indicate that the cats can be accessed through the rear flue plate. I have tried and failed. I can't come up with a way to rotate them from that position to get them to come out from there. If the stove were rear vented we could replace the cats either by reaching up from inside the box with the baffles removed, or reach down through the top-flue instead, (presumably, it would have the cover plate installed on top instead).

If the stove had a way to extract more heat from the cats into the stove body, then it would have lower EGT's, which is something you seem to be concerned about with the advise to go double wall on these. The current configuration, is apt to produce higher EGT's, which would seem well suited to drive single wall effectively. By leaving those last few percetage points of efficiancy on the table they may actually be "tuning" the stove to be more broadly compatible. More on this in a moment...

I was just browsing through a whole bunch of forum posts through the brand specific part of the forum and it's just an endless series of stoves installed with double wall that are over-firing. Like, there must be hundreds of examples of this on the forum. Are we really certain that all these installations should be double wall? I understand that for install clearances to combustibles it is sometimes required, but I suspect a lot of these stoves are being installed with double wall just because that's the general consensus recommendation on here. Seems like there's a theme developing. Double wall = over-fire. The dampers only seem to help if modified, and are a source of smoking up rooms when operators forget to open them when the stove door is opened.

What if there were a system, that would produce greater and greater draft correction factor the higher the temps in the system went? Kinda like a passive but automated process for applying more brakes as the temps go up...

As it turns out, the EPA test configuration with stoves, If I understood the diagrams correctly, has about 8 foot of single wall and 8 foot of insulated class A pipe above the stove for testing. That's the "standard" that stoves are being tuned for, and then out here in the real world we're putting double wall almost everywhere as the default. In doing so we're guaranteeing that we're going to get a lower thermal efficiency from the system than the test configuration would have, all out of concern for keeping a clean chimney in an era where stoves are burning with 10-100X lower emissions than they did just 30-40 years ago and maintaining higher EGT's through the burn cycle since so many more of those emissions are being converted to thermal energy. I'm sorry but this itch to double wall everything is just sounding more and more bogus the more I contemplate it.

My chimney system is cleaner with single wall than with double wall because it can be driven at the temperate the stove wants to operate at with a full load of wood without snowballing, and with the knowledge there's more heat being dissipated into the house I'm fine with running those higher EGT's. If I had double wall with a damper I'd be inclined to choke down the stove to stay under 600F EGT most of the time to waste less heat. The lower burn rates required to do that, combined with the lower EGT's, would almost certainly produce as many or more deposits on the chimney system. The system seems like it was tuned for single wall, and double wall creates problems that have to be corrected with stove mods and pipe dampers.

I live at 7400' elevation, my total chimney height it about 21' which should be just about right without a damper if this system was tuned for sea-level with a 16' damper-less pipe. The "extra" 5 feet (~63%) compared to the EPA test config is on the single wall side and is being driven by a stove that is about 63% larger than the smallest in this range of stoves with similar operating characteristics. Working great this way so far!

Yes, but the dilution tunnel does not asperate to the outdoors. It goes into a draft hood that has (as @bholler pointed out) controls the "draft". The amount of CFM allowed within the test method it supposed to be sufficient to eliminate excessive moisture on sampling equipment and filters.

As to the "over firing" you must remember, the ability to reduce the amount of air flow into the firebox is decreased with the lower EPA emission standards. So when the stack effect is increased (excessive draft) the consumer is not able to stop the excessive influx of air. The cfm's increase exponentially and therefore subject to over firing. This doesn't happen in the lab, because we can control the cfm with the fan in the draft hood. In the real world, people buy those things you stick in pipe to reduce draft. (Some guys will get a laugh out of this wording).

I'm certain your stove will perform to your satisfaction and give you many years of warmth.

BKVP

 

[mdocod]

It's important to understand that the reason most people first post on hearth.com is that they have a problem. What we don't see are the thousands of people that are not having issues.

It's pretty rare to see a posting here for a cat stove that is overfiring. That may change with the hybrids, but a cat stove is better with double-wall stove pipe due to the lower flue temps when run low and slow. It sounds like the Mansfield is capable of this. If you are running the stove in spring with outdoor temps in the 40-50º range then the flue may see more creosote accumulation, or maybe not. Like I said, this is a new model. The other factor is the exposure of the chimney system. A straight up through the house system is going to stay warmer and cleaner than one that is exterior with tens of feet exposed to cold weather.

Note that a lot of people that post are novice burners, especially this year. Many don't know how to operate the stove correctly yet and are afraid of a brisk fire. That is different from an actual overfire. Mostly the hot fire is caused by the operator not turning down the air soon enough and loading it improperly. Sorting all through that, once the user learns how to load and run the stove correctly, the overfire issues are a small fraction of postings here.

I look forward to hearing more about the stove. The high EGT surprised me. Our non-cat stove usually runs about 600-650º with no damper and double-wall stove pipe. Though when I need more heat it will get up to 700º for an hour or so if pushed.

The same stove-pipe/chimney system was making 2 different stoves over-fire at full choke. I don't think there was a "learning curve" that could correct it. I tried all sorts of things and I'm pretty thorough. The only solution on the double wall was small fuel loads and early full-choke, and then having to come back later in the burn cycle to open it back up so it could finish the burn properly/cleanly.

Any scenario where "full choke" isn't capable of drawing the stove back the other direction is a problem IMO...

We have around 21-22' of total chimney length at 7400' elevation. This shouldn't need dampers up here. On single wall the full-choke setting will turn the corner and pull an over-excited fire (1000F EGT) back down to very comfortable/safe levels steadily over the course of 5-10 minutes. (~600F and falling). Perfect.

I would not characterize the Mansfield as a wood gasifier that can run super-low-and-slow the way a BK or other dedicated cat stove can operate. It doesn't work right when forced to run this way and the cats will usually overheat if too much of the combustion is shifted to them. I would characterize this stove as being able to burn slightly slower than a well tuned non-cat stove, and perhaps, most importantly, it "cleans up" the messy transition out of the gaseous flaming stage to the coaling stage more elegantly, maintaining higher EGT's and cleaner exhaust through this part of the burn than we would get otherwise (400-500F). I'm really not that concerned about creosote from this stove but will be monitoring for it. It deposits the same "pine soot" that anything around here will get from burning trash wood. That stuff fluffs off with a quick sweep super easy and is accumulating slower on the single wall run hot with big fuel loads than the double wall run cold on small fuel loads to prevent snowballing.

The "holy grail" of a stove is something that can be "set and forget" through a burn cycle. Since swapping to single wall, this stove runs burn cycle after burn cycle like this with no issues. Perfect burn after perfect burn. It works as if there's an Arduino taking measurements and setting the air control but all I'm doing is leaving the air control at 1/4" as specified in the manual. There is no incentive to "fix" this. I think the use of single wall needs to be considered in the big picture of stove installs as part of the whole equation. There's a lot of variables to consider and every one of them is pulling one way or another. The right answer is the one that works.

 

[begreen]

There's a lot of variables to consider and every one of them is pulling one way or another. The right answer is the one that works.

Agreed, as long as it works safely. We're a long ways off from the OP's question. Too bad. There are 3 topics floating in this thread. The Mansfield info is interesting but off the topic or is this to encourage running it for extended periods of time with the bypass open?

 

[mdocod]

Testing is generally done with an exhaust fan pulling the draft specified by the manufacturer. This is so they can test consistently every time. And why it's important to install stoves in a way that is as close as possible to that draft specification.

The diagram I saw showed the exhaust fan drawing in the fumes from a hood mounted above the top of the chimney system. The duct with the fan was not connected to the chimney system directly.

If they are just going to pull the specified vacuum into the she test system directly, why even bother with the chimney system?

 

[mdocod]

That absolutely is not the reality of what happens in the field. Stove over fire either because of excessive draft or user error not double wall pipe. Yes the increased flue temps from double wall pipe will increase draft by a few percentage points but really not enough to make a difference

I'm sorry but if the single wall only impacts this by a few percentage points, "not enough to make a difference" then the entire narrative that the forum regulars have taken a stance on about my single wall installation makes no sense.

It either does make a big difference and there's cause for concern and observation, or it doesn't make a big difference, in which case there isn't cause for concern and observation.

I'm aware of the cause for concern and the system is under observation. It's doing a lot more than a "few percent."

 

[bholler]

I'm sorry but if the single wall only impacts this by a few percentage points, "not enough to make a difference" then the entire narrative that the forum regulars have taken a stance on about my single wall installation makes no sense.

It either does make a big difference and there's cause for concern and observation, or it doesn't make a big difference, in which case there isn't cause for concern and observation.

I'm aware of the cause for concern and the system is under observation. It's doing a lot more than a "few percent."

It absolutely makes a big difference in keeping temperatures up in the chimney better. It doesn't increase draft enough to cause overfires in lots of stoves as you implied.

 

[mdocod]

It absolutely makes a big difference in keeping temperatures up in the chimney better. It doesn't increase draft enough to cause overfires in lots of stoves as you implied.

It's not an implication, it's not guesswork. I ran 2 different stoves in the same exact spot, with both kinds of pipe and watched them work like absolute garbage on the double wall and work perfectly on the single wall.

 

[bholler]

It's not an implication, it's not guesswork. I ran 2 different stoves in the same exact spot, with both kinds of pipe and watched them work like absolute garbage on the double wall and work perfectly on the single wall.

Well that is absolutely not typical of what I see in the field or on here. Almost every time I switch a stove to double wall performance increases. What problems were you having while running double wall? What is your setup like?

 

[mdocod]

Well that is absolutely not typical of what I see in the field or on here. Almost every time I switch a stove to double wall performance increases. What problems were you having while running double wall? What is your setup like?

Setup is simple:



Straight shot of stove pipe ~13' to the bottom of the support box. Another ~8-9' of straight class A chimney system from there.

This stove calls for 13' - 27' of total chimney system vertical height from the top of the stop.

We are right in the middle of the recommendation and at 7400' elevation. With elevation correction considered we're probably at the lower end of the range of "effective" chimney height.

I bought a vacuum gauge but it doesn't seem to work right.

------------------

On double wall, both stoves ran like a nuclear power plant without enough control rods to manage the reaction. Allowing EGT's to creep above 600-700F could be the beginning of a non-reversable uncontrolled over-fire.

Saw red on the steel stove and had measured surface temps on the soapstone over 650F.

Required constant supervision, smaller fuel loads, and adjustments to keep in check on both stoves, often full-choke, but of course, later in the burn they would both have to be opened back up in order to complete the burn cycle cleanly.

-----------------

On single wall, full loads of wood burn through at the manufacture recommended air control settings without any adjustments required after the start-up process, while maintaining ideal temps through the burn cycle, all while putting more heat in the house. It's repeatable and can be trusted while sleeping and leaving for work.

 

[BKVP]

I might add, it is illegal to operate a stove or instruct a consumer to use a stove other than as tested. This comes straight out of the 2015 New Source Performance Standards. You can access all manufacturer test reports on manufacturer websites. You can read precisely how the stove was operated during each of the test runs. I can state we would steadfastly instruct users to operate the stove as per the Owners & Operators Manual that is supplied with each of our products. Failure to do so will void the warranty.

Did you know:
40 CFR Part 60
60.533 (6)
"A copy of the warranties for the model line, which must include a statement that the warranties are void if the unit is used to burn materials for which the unit is not certified by the EPA and void if not operated according to the owner's manual."

A new thread could be started to discuss the differences of single wall stoves pipe vs double wall stove pipe.