Blaze King King 40 New Cat Stove 2020 Smoke Smell

RogueChili

New Member
Feb 21, 2021
36
USA
Hi all! New to forum, hope to find good information for puzzling issue.

Recently installed the new King 40 and am experiencing intermittent smoke smell during operation. I want to start the thread in hopes of connecting to other King 40 owners experiencing similar issues. My feeling is there is inherent design issue with this latest version of the stove.

I have determined the smoke is exiting around the door, it is difficult to pin point the exact spot however it appears to be located at the hinge size near the top.

A little info regarding the install:
  • Vertical flue pipe - 8" double wall 28 inch from stove top to bottom of 90 degree elbow; 18" long 8" double wall horizontal pipe into thimble
  • Masonry chimney with 8x12 clay liner 24 feet tall from stove top; 90 percent of masonry chimney is free standing and internal to house
  • Draft measured between .04 and .06 inches H2O during all modes of operation at stove collar
  • No smoke spillage when lighting fire or when re-loading
  • When smoke smell is detected and door is opened, air rushes in and no smoke escapes the stove
Manufacturer says stainless liner is required, improve draft, the magic bullet! I would expect if draft was an issue the stove would not preform properly however not the case, the stove burns perfectly from low to high settings, cat temperature is good, heat output is good, and the stove responds to temperature adjustments very quickly.

Any information will be appreciated!
 
Last edited:

kennyp2339

Minister of Fire
Feb 16, 2014
5,629
07462
1st change out the 90 deg elbow w/ (2) 45's
 
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stoveliker

Minister of Fire
Nov 17, 2019
553
Eastern Long Island NY
Apart from the two above posts (and I agree that if trouble appears, the first thing to do is to make the system compliant with the requirements given with the stove...), I suggest to check the seal of the door (dollar bill test). No smell is supposed to be able to come out thru your door gasket if it closes properly.
 

jetsam

Minister of Fire
Dec 12, 2015
5,094
Long Island, NY
youtu.be
My first step would be to be to tear out that venting and do it so it meets minimum requirements and is insulated (break out the old liner, drill a new hole higher up, fully line it with 8" insulated liner).

Even if you resolve the smoke smell, it will likely be a real creosote factory in shoulder season, and I have to imagine you'll have other draft problems cropping up as the weather warms (though if you only plan to use it for supplemental heat in real cold weather, that will mitigate a lot of the warm-weather problens).

I'm not even saying that your venting is necessarily connected with your smoke smell, but it's a bad enough problem on its own that I would want it redone ASAP.
 
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MissMac

Minister of Fire
Dec 4, 2017
740
NW Ontario
I believe it is very important to meet the manufacturer's specifications for the chimney length/configuration, especially if you're trying to dial down your stove to enjoy those low and slow burns. From what I understand, BKs are a bit more particular about needing good draft than some other stoves in order for them to work as designed, so I'd address your system and get it up to at least the minimum specs as provided by BK. Good luck!
 

RogueChili

New Member
Feb 21, 2021
36
USA
My original post was in error and updated, the vertical flue is 28" well within specifications .

Regarding the door gasket, woven glass rope is not air tight and has some permeability. These gaskets depend on the inside pressure be lower than the outside pressure which must not be the case.

Regarding the 2 45's, what is the difference in flow resistance between 1 90 and 2 45's ? Looking over some design guides it seems small, the k =.75 for a single 90 and .25 for a single 45. I expect two 45's would be somewhere greater than .5 and less than .75 due to the interaction between the two. Have not found the tables for this combination.

All responses point to draft, so please provide real numbers, what is the draft specification, min / max and where is it measured? I can make these measurements to prove or disprove the venting system is failing. To date I have only measured the draft at the collar and it proves to be in the range of .04 to .06 inches of H2O.
 

stoveliker

Minister of Fire
Nov 17, 2019
553
Eastern Long Island NY
Correct, gases do not leak from a gasket (however impermeable) if the draft (underpressure in the stove) is ok. (Flow thru the leaking gasket would be into the stove.)

However, even if the draft is NOT ok, a properly sealing gasket even when not airtight (which is a misnomer because even for an ultrahigh vacuum system with a base pressure of 10^-11 mbar, (copper) gaskets have a certain leak rate) would NOT give you smells in the home.
 

stoveliker

Minister of Fire
Nov 17, 2019
553
Eastern Long Island NY
My BK when turned down in vapor fuel rich situation will leak a little smoke out when they light off POOF!
Then adjust the door handle thing (forgot the name, see the manual). That's not supposed to happen.
When the gases go poof (secondary explosion), the pressure burst is very small and you should not have the door pop out a bit and you should not smell anything. If you do, the sealing of the door is not as it should be.
 

RogueChili

New Member
Feb 21, 2021
36
USA
Correct, gases do not leak from a gasket (however impermeable) if the draft (underpressure in the stove) is ok. (Flow thru the leaking gasket would be into the stove.)

However, even if the draft is NOT ok, a properly sealing gasket even when not airtight (which is a misnomer because even for an ultrahigh vacuum system with a base pressure of 10^-11 mbar, (copper) gaskets have a certain leak rate) would NOT give you smells in the home.
Agreed, and that is what puzzles me., there should never be high pressure, relative to the room, in the stove regardless of what the draft is. And as I mentioned, while the fumes are coming out through the gasket and if the door is opened air rushes in and no additional gases come out into the room which implies there is sufficient draft.
 

stoveliker

Minister of Fire
Nov 17, 2019
553
Eastern Long Island NY
That suggests that the pressure in your home, relative to that in the stove, is not constant. I.e. there is something competing with the draft (lowering the pressure in the room to below that inside the stove), and doing so in an intermittent way.

Maybe try to switch off all other appliances (e.g. gas or oil furnace, bathroom fans, cooking exhaust fan etc), and crack a window on the same level as your stove, and see if it still happens.
 

RogueChili

New Member
Feb 21, 2021
36
USA
That suggests that the pressure in your home, relative to that in the stove, is not constant. I.e. there is something competing with the draft (lowering the pressure in the room to below that inside the stove), and doing so in an intermittent way.

Maybe try to switch off all other appliances (e.g. gas or oil furnace, bathroom fans, cooking exhaust fan etc), and crack a window on the same level as your stove, and see if it still happens.
Two things, the measurement device I use to measure the draft is in the room so the measurement is relative to the room. And in addition I have tested with windows open which did not resolve it.
 

stoveliker

Minister of Fire
Nov 17, 2019
553
Eastern Long Island NY
Well, physics dictates that gases don't flow up the pressure hill (thru the gasket to outside the stove). So something is awry with either your chimney, or the pressure in your home. And it may be intermittent (in which case it is most likely the latter).
 

RogueChili

New Member
Feb 21, 2021
36
USA
Well, physics dictates that gases don't flow up the pressure hill (thru the gasket to outside the stove). So something is awry with either your chimney, or the pressure in your home. And it may be intermittent (in which case it is most likely the latter).
You know I thought the same thing and that is why I bought the gauge to measure draft. And I can tell you when gas is exiting the door I am staring at the gauge and it reads .05 inches of H2O and that is relative to the room. Doesn't make any sense!
 

stoveliker

Minister of Fire
Nov 17, 2019
553
Eastern Long Island NY
You know I thought the same thing and that is why I bought the gauge to measure draft. And I can tell you when gas is exiting the door I am staring at the gauge and it reads .05 inches of H2O and that is relative to the room. Doesn't make any sense!
Going out on a limb here: UNLESS you have an (significant) impedance between the firebox and the location of your gauge.
 

RogueChili

New Member
Feb 21, 2021
36
USA
Going out on a limb here: UNLESS you have an (significant) impedance between the firebox and the location of your gauge.
Well, all I can say is the gauge is within a foot from the door and the tube length is only about 3 feet which should not be an issue sense there is no high flow, more of a static pressure. I also measured at the hole above the CAT and get similar values. I am trying to decide the next best place to take measurements but am waiting for more responses on the subject. Any other area measurements will require the drilling of holes to access so would like to keep it to a minimum.
 

kennyp2339

Minister of Fire
Feb 16, 2014
5,629
07462
Well, all I can say is the gauge is within a foot from the door and the tube length is only about 3 feet which should not be an issue sense there is no high flow, more of a static pressure. I also measured at the hole above the CAT and get similar values. I am trying to decide the next best place to take measurements but am waiting for more responses on the subject. Any other area measurements will require the drilling of holes to access so would like to keep it to a minimum.
Buy a probe thermometer for your pipe, drill approx a foot above the collar, also use same hole to test draft, you want .05wc" while the stove is running on high setting.
As far as intermittent smoke smell, does the gasket have an equal knife edge mark all the way around? is there any discoloration beyond the knife edge mark, I know my gasket looks pretty dirty on the inside knife mark and its white after the knife mark (3 seasons on it) If you do take the gasket off, also check the glass retention bolts that hold the window, a bolt or two could be loose.
The one thing that needs to be remembered here is the BK base air input (when the t-stat is totally closed) is much smaller then other stoves, so if you hit temp and the t-stat closes then your essentially running on the hole, if your draft is minimum you can experience different issues, the more common would be cat stalling, but if you have a marginal set up like yours you could have smells due to turbulence of smoke (2) 90's fairly close to each other (elbow then crock into the unlined masonry chimney)
The other issues is flue gas condensation, since the King is designed to smolder and burn smoke for heat production on lower settings your flue gasses are much colder then other stoves (why an insulated liner is highly recommended even on interior chimney's), cooler flue gasses are more stagnated in nature, and if you have a leaky chimney (due to gaps at the black pipe connection or a poorly sealed clean out door) you'll have even slower issues. No one asked yet, but what kind of cap do you have?
 
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RogueChili

New Member
Feb 21, 2021
36
USA
Buy a probe thermometer for your pipe, drill approx a foot above the collar, also use same hole to test draft, you want .05wc" while the stove is running on high setting.
As far as intermittent smoke smell, does the gasket have an equal knife edge mark all the way around? is there any discoloration beyond the knife edge mark, I know my gasket looks pretty dirty on the inside knife mark and its white after the knife mark (3 seasons on it) If you do take the gasket off, also check the glass retention bolts that hold the window, a bolt or two could be loose.
The one thing that needs to be remembered here is the BK base air input (when the t-stat is totally closed) is much smaller then other stoves, so if you hit temp and the t-stat closes then your essentially running on the hole, if your draft is minimum you can experience different issues, the more common would be cat stalling, but if you have a marginal set up like yours you could have smells due to turbulence of smoke (2) 90's fairly close to each other (elbow then crock into the unlined masonry chimney)
The other issues is flue gas condensation, since the King is designed to smolder and burn smoke for heat production on lower settings your flue gasses are much colder then other stoves (why an insulated liner is highly recommended even on interior chimney's), cooler flue gasses are more stagnated in nature, and if you have a leaky chimney (due to gaps at the black pipe connection or a poorly sealed clean out door) you'll have even slower issues. No one asked yet, but what kind of cap do you have?
Excellent explanation of the working system and contributing factors!

One question though, why do you say i have a unlined masonry chimney? There are beautiful clay tiles lining it, and from camera inspection the joints are almost perfect aligned and almost no trace of cement hanging inside.

As far as signs of leaking around the gaskets there are none. I have been going through this stove with a fine tooth come trying to understand the forces involved in pushing gases "through" the door gasket, also the glass is secured properly.

No leaks from the pipe or the connection at the collar or thimble, I have verified this 100% with a simple sniffer tool made with foil and shaped like a long funnel. This allows to pin point fumes from a three foot distance keeping myself out the the heat turbulence from the stove. The joint to the thimble is air tight, caulked and secured with two screws.

About the draft, when the stove is on high the draft measures between .05 and .06wc, when the stove is at 20% it measures between .04 and .05 wc about 4 inches above the collar. I might note that similar values are measured in the hole above the cat.

These measurements tell me the draft is sufficient and makes me suspect something very difficult to grasp is causing localized high pressure around the the door gasket.

These facts lead me to believe this theory:
  • gases are exiting around the door through the gasket
  • WC >= .04 above collar
  • opening the door slightly the fire rages and no more gases exiting (if draft is issue how is this possible?)
One thing you said(King is designed to smolder) sparked a thought, is it possible the gas leak is happening only when the flame is extinguished? So in the slow mode it would be more prevalent, in the mid range intermittent, and in the high range when the flame is pretty much constant, un-detectable. All this is dependent on ambient temperatures however lets assume in the mid operating temperature range the thermostat control is moving from closed to some percentage open to maintain the set temperature, when it is closed the flame is out and the coals smoldering, when open the flame is re-established. This seems to track with what I have experienced over the trouble shooting process. Very interesting!
 

Nealm66

Minister of Fire
Sep 25, 2020
818
Western Washington
Maybe there’s something wrong with the cat? What happens if you turn it down with the bypass open? I don’t know crap so excuse if this is a stupid idea. I’ve ran my stove a few times on low with the bypass open on accident. It’s a creosote maker but it still ran ok
 

MissMac

Minister of Fire
Dec 4, 2017
740
NW Ontario
Maybe there’s something wrong with the cat? What happens if you turn it down with the bypass open? I don’t know crap so excuse if this is a stupid idea. I’ve ran my stove a few times on low with the bypass open on accident. It’s a creosote maker but it still ran ok
i don't think i would even try this, because it's not how the stove is designed to be run and goes against the manufacturer's instructions.
 

RogueChili

New Member
Feb 21, 2021
36
USA
Maybe there’s something wrong with the cat? What happens if you turn it down with the bypass open? I don’t know crap so excuse if this is a stupid idea. I’ve ran my stove a few times on low with the bypass open on accident. It’s a creosote maker but it still ran ok
Actually, that is a good idea, the cat is basically a flow resistance between the combustion chamber and the exhaust side which will cause some pressure drop. When the stove was in the leak mode I did just that, opened the bypass and checked periodically for gas escaping the door, I found that the gas was escaping in either state of the bypass however possibly not as much in the bypass mode, it is difficult to say for sure due to so many variables.
 

moresnow

Minister of Fire
Jan 13, 2015
1,667
Iowa
Post a pic of your install. Where are you located? Elevation? What type of wood are you using?
 

RogueChili

New Member
Feb 21, 2021
36
USA
Altitude around 700', the video shows the draft measured while fumes were escaping from the door gasket.





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