on a cold start with the above technique (closed primary) I noticed some smoke coming from under the stove. My assumption is that it was from the air intake under the stove (where else could it have came from?). it didn't come out the door as i saw flames/smoke going over the baffle and up the flue. my only thought was that maybe with the primary closed and the door wide open, air/smoke could be getting pushed up into the air wash and then come out the air intake?
Hearthstone Shelburne 8372 Operation
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update:
I've found that lowering the primary to what the manual considers "medium-low burn" all but eliminates smoke rollout on start-up/reload.
I've also figured out that I just wasn't closing the primary down quickly enough. Thanks to @begreen for pointing out that the primary isn't linear. I'm able to maintain 400, 500, etc if I shut down quickly enough. On reloads I maintain "steady" flames (by turning down the air as needed) until the by-pass is closed and STT is above 400. Then I start to turn down the air with the intention of getting it to a "cruise" setting. This has been creating good secondaries and not letting the temps get away from me.
The manual says to stuff it full and run it wide open for 20-45 minutes once or twice a day. I loaded it maybe 50% full and tried this and I'm fairly confident I would have had a glowing stove had I not taken some measures to lower the temp. STT was 640+ and rising and the flue (single wall) was 445+ and rising. Maybe it would have peaked at 700 but I didn't want to flirt with that with the settings wide open and running full speed ahead.
I've found that lowering the primary to what the manual considers "medium-low burn" all but eliminates smoke rollout on start-up/reload.
I've also figured out that I just wasn't closing the primary down quickly enough. Thanks to @begreen for pointing out that the primary isn't linear. I'm able to maintain 400, 500, etc if I shut down quickly enough. On reloads I maintain "steady" flames (by turning down the air as needed) until the by-pass is closed and STT is above 400. Then I start to turn down the air with the intention of getting it to a "cruise" setting. This has been creating good secondaries and not letting the temps get away from me.
The manual says to stuff it full and run it wide open for 20-45 minutes once or twice a day. I loaded it maybe 50% full and tried this and I'm fairly confident I would have had a glowing stove had I not taken some measures to lower the temp. STT was 640+ and rising and the flue (single wall) was 445+ and rising. Maybe it would have peaked at 700 but I didn't want to flirt with that with the settings wide open and running full speed ahead.
I have similar/exact directions on my Manchesters manual for the wide open part. Yeah even with my crappy draft that would present a quick over fire. I always scratch my head when i hear that direction, you would think if anything they would be more conservative with the time
In the manual it says to leave a valley in the coals behind the primary air inlet. I was doing this and it was creating a pathway for flames to catch the entire load. Loading the box almost full resulted in a large off-gassing event where temps would peak above 750 regardless of the air setting. I've changed to:
- pulling all of the coals forward such that the back stack of logs isn't on any coals
- making sure the coals/ash aren't blocking the air inlet but not creating a valley; basically just creating a depression to allow air in
- depending on log size put another stack in front of the back stack; pushing them into the ash/stone on the bottom of the firebox to mitigate paths for air to ignite the whole load
- add kindling/small split directly on top of coals
- don't engage cat until front logs are fully engulfed in flames
- reduce air 50% of travel around 450 F STT
- try to keep flue below 320 (single wall); this is the real metric
- reduce air depending on desired heat out-put
just wanted to follow up on this. I haven't had any run-away stove scenarios since implementing this type of routine. I've loaded N/S, E/W up to the baffle and have been able to keep the top temp right around 600.
Thanks for the update. These steps are similar for many non-cat and hybrid stoves. Flue temp is more important than stovetop temp, especially on cold startups.
Can you tell us more about routine maintenance? How often have you cleaned the cat of ash?
Can you tell us more about routine maintenance? How often have you cleaned the cat of ash?
Hasn't been much routine maintenance during the season honestly.
I've been cleaning the cat every ~6 weeks or so. This is usually prompted when I noticed a large decrease in draft when engaging the cat. Although, I have reloaded a couple of times with the cat engaged and I'm sure the fly ash during that has contributed to the plugging. I'm also burning 100% white ash so there's a lot of it.
The glass has been staying extremely clean. I basically only wipe a white haze off when I clean the cats.
The Cap/Screen of the chimney doesn't look to have any build-up on it. The inside surface of the top of the cap will get black but I usually burn wide open for ~20 minutes a day and that'll clear it up. When I pulled the smaller un-insulated
Decided I want to update my flue setup again. The rear install is something like the image below now with an adjustable elbow that is more or less (2) 30-degree elbows butted up to one another to make up a difference of 3" in height between the stove exit and my thru-wall thimble. I'm not totally satisfied with the integrity of the pipe in this orientation and I assume changing it to a straight pipe would improve draft/performance (albeit maybe slightly). To make up the difference in height I'm going to put the stove on 3" thick concrete blocks (probably these: lowes retaining wall blocks). If I like the setup and performance seems to improve I'll spend the time next year to lay a layer of bricks/mortar to replace the concrete blocks.
![[Hearth.com] Hearthstone Shelburne 8372 Operation](https://www.hearth.com/talk/data/attachments/315/315110-3770950cc272344efddec02eb09dddfe.jpg?hash=JbGbbO4_ce "[Hearth.com] Hearthstone Shelburne 8372 Operation")
Hearthstone support is pretty useless and the manual has conflicting statements about minimum chimney height requirements for the 8372 Shelburne in a rear exit configuration. So I'll assume the 16.5 ft from the top of the stove to the top of the chimney is the correct statistic. BlazeKing has a table for chimney height recommendations based on elevation above sea level and chimney components in your system (elbows, etc). My assumption here is that I can just plug my minimum height requirement in and use their height recommendations in kind.
I'm at ~500 ft and with the modifications mentioned above will have ~2.5 ft horizontal run and a T "section". So based on the below that says I need minimum height (16.5ft) + 8 ft = 24.5 ft. The current chimney is 21.5 ft from the top of the stove, so that means I'd need another 3 ft section of class A. Does this seem correct?
![[Hearth.com] Hearthstone Shelburne 8372 Operation](https://www.hearth.com/talk/data/attachments/315/315112-73e607701ce3aea33b7acac9b4d81248.jpg?hash=uvvDfx3DIo "[Hearth.com] Hearthstone Shelburne 8372 Operation")
Hearthstone support is pretty useless and the manual has conflicting statements about minimum chimney height requirements for the 8372 Shelburne in a rear exit configuration. So I'll assume the 16.5 ft from the top of the stove to the top of the chimney is the correct statistic. BlazeKing has a table for chimney height recommendations based on elevation above sea level and chimney components in your system (elbows, etc). My assumption here is that I can just plug my minimum height requirement in and use their height recommendations in kind.
I'm at ~500 ft and with the modifications mentioned above will have ~2.5 ft horizontal run and a T "section". So based on the below that says I need minimum height (16.5ft) + 8 ft = 24.5 ft. The current chimney is 21.5 ft from the top of the stove, so that means I'd need another 3 ft section of class A. Does this seem correct?
the liner is insulated; the original install it was not and undersized. since then I replaced the liner with a 6" that I insulated and then added class A above the brick chimney.
the stove showed some problems when outside temperatures increased. if it was above 40 it was hard to sustain secondary combustion, and smoke rollout during reloads was almost a guarantee.
This is not uncommon with shallow fireboxes, especially when rear-vented. Will 3' more chimney be added before the season begins?
My plan was to clean/inspect the chimney before the season starts. While I'm up there it wouldn't be too much more trouble to add another 3 ft of class A. That is if the guidelines above make sense and 3 ft will make a difference.
As a test you could insert a 3 ft section of cheap 6" round, warm air duct into the top of the chimney and see if there is a notable difference.
True, I'd prefer to not have to get back up on the roof though. And based on the weather around here recently I won't be using the stove anytime soon.
Given the smoke roll-out on reloads at "higher outdoor temps" I assume that increasing the chimney won't negatively affect anything right?
How much class A chimney is already attached to the masonry chimney? I'd be a bit concerned that at some point, the leverage of the unbraced pipe might become an issue.
It's good to see that it's braced. That should be tall enough. Does opening a nearby window an inch or so, before opening the stove door, help at all?
I don't believe I observed an open window improving roll-out on reloads. When starting a fire (after pre-heating the flue) I always have a window cracked. If I leave the stove door open sometimes the smoke will get pulled up the flue, other times it'll rollout.
I just came to a realization that maybe Hearthstone's minimum rear exit height requirement may already take into account a T "section" in the chimney. In which case, my additional height requirement would come down to just my horizontal pipe length and the adjustable elbow. According to the blaze king chart above (2x30 degrees) means +3ft to chimney height. If I were to remove that then I just have to add in the additional height for my 2.5 ft horizontal pipe (+5 ft). That would put me at a required 24ft from the floor; the current system is 23 ft.
Chimney location on the house, local terrain, and local weather can affect draft too. This may relate to the intermittent nature of the rollout. This may not be solvable by just adding height. A deeper firebox might. Do you start the fires top-down?
When it was above 45º we had smoke rollout with the Castine with a rear vent to an elbow then straight up 20 ft. When we put the stove in the installers were concerned about this, but the rear vent + elbow was needed to achieve safe clearances in our corner install. The T6 that replaced that stove is top-vented and does not have this issue until around 55º and then it can be avoided with top-down starting.
When it was above 45º we had smoke rollout with the Castine with a rear vent to an elbow then straight up 20 ft. When we put the stove in the installers were concerned about this, but the rear vent + elbow was needed to achieve safe clearances in our corner install. The T6 that replaced that stove is top-vented and does not have this issue until around 55º and then it can be avoided with top-down starting.
Cleaned the chimney top down. Cap was pretty much clean and class a had some light black granular coating. It all came off with the cleaning. Haven't vacuumed it out yet so I don't know total amount of soot that I got out of it.
While I was up there I added another 4 ft section of class A in hopes of finally fixing my smoke rollout issue. Total height is ~25 ft from stove exit.
![[Hearth.com] Hearthstone Shelburne 8372 Operation](https://www.hearth.com/talk/data/attachments/316/316345-71b2dbc440eede9b1bd7803d10e9f723.jpg?hash=ouHWQP5mUf "[Hearth.com] Hearthstone Shelburne 8372 Operation")
While I was up there I added another 4 ft section of class A in hopes of finally fixing my smoke rollout issue. Total height is ~25 ft from stove exit.
A. How the hell were you able to get up that high to extend it or did you take all the class a down and twist on the extension and put it back up?
B. I’m thinking of adding another couple feet to
my 4’ class a chimney extension on my masonry chimney like yours (i’ll need to add a brace as well) Never had to twist them together, how easy is it to twist them? Are they easy to twist off when they’ve been sitting there for a year?
B. I’m thinking of adding another couple feet to
my 4’ class a chimney extension on my masonry chimney like yours (i’ll need to add a brace as well) Never had to twist them together, how easy is it to twist them? Are they easy to twist off when they’ve been sitting there for a year?
I pulled it all off, added the additional height and then put it back on. It was not as easy as that though. Total weight is probably only 60lbs but cantilever stuff out 9.5 ft and you can imagine how you have to wrestle with it. Disclaimer, if I didn't go to the gym religiously it would have been a lot harder.
These don't twist together. It's 3 screws per connection. The slip fit is pretty tight though. They came apart relatively easily after a year.
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