Cat operating temperature

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neverstop

Member
Oct 11, 2020
123
new hampshire
Im curious about normal operating temperatures for cats. I have a Hearthstone shelburne stove and my recent burn the temp above the cat continued to rise after I engaged it even at the lowest primary air setting. I even saw fire below the cat at one point. Here are pictures of the stove top temp (green/black) and above the cats (silver/orange), as well as the cats glowing themselves and the dummy cat thermometer provided with the stove.

Is this normal operation? Could I have avoided this by engaging them earlier?

20211127_181422.jpg 20211127_181439.jpg 20211127_181432.jpg
 

begreen

Mooderator
Staff member
Nov 18, 2005
92,752
South Puget Sound, WA
Catalysts operate between 500-1600º. You should be able to engage it as soon as the cat gauge gets into the active (silver) zone.

I wouldn't trust the old Rutland thermometer to be accurate. What is the temp if you swap out the other thermometer at that location?

PS: The black thermometer is a flue thermometer. The scales (Best Operation/Too Hot) are for single-wall stove pipe. You are ok running the stove in the 5-700º range.
 

neverstop

Member
Oct 11, 2020
123
new hampshire
Catalysts operate between 500-1600º. You should be able to engage it as soon as the cat gauge gets into the active (silver) zone.

I wouldn't trust the old Rutland thermometer to be accurate. What is the temp if you swap out the other thermometer at that location?

PS: The black thermometer is a flue thermometer. The scales (Best Operation/Too Hot) are for single-wall stove pipe. You are ok running the stove in the 5-700º range.
Yeah I bought that by accident and ignore the ranges and look at the temps. The Rutland matches when both are on the stove top. But that circular piece the Rutland is attached to is separated from the rest of the firebox internally when the cats are engaged, so it has been reading higher but this was way higher than I've seen it yet.

So that portion should be reading hotter, and 900º is ok?

I'd like to run the stove at 350-400 cause I don't need all the heat right now. I think I've been waiting too long the engage the cat.
 

tabner

Feeling the Heat
Jan 17, 2019
261
Eastern CT
But that circular piece the Rutland is attached to is separated from the rest of the firebox internally when the cats are engaged,
Is that circular piece basically the plug over the hole for a top vent setup? and you have it rear vented?
I'm not sure what the temps should be on it, but it makes sense they'd be pretty high. The cats face vertically in this stove, and they sit right below that top vent hole, so you'd be getting all the heat from the cats pushing directly into that piece, so I'm not surprised it's hot there.
 

neverstop

Member
Oct 11, 2020
123
new hampshire
Is that circular piece basically the plug over the hole for a top vent setup? and you have it rear vented?
I'm not sure what the temps should be on it, but it makes sense they'd be pretty high. The cats face vertically in this stove, and they sit right below that top vent hole, so you'd be getting all the heat from the cats pushing directly into that piece, so I'm not surprised it's hot there.
Yes that is exactly what the circular piece is, and yes the cats sit directly below this and face vertically.

Do i need to wait until the entire wood load is charred prior to engaging the cat? Also, once I engage the cat can I cut the primary air down right away?
 

tabner

Feeling the Heat
Jan 17, 2019
261
Eastern CT
Yes that is exactly what the circular piece is, and yes the cats sit directly below this and face vertically.

Do i need to wait until the entire wood load is charred prior to engaging the cat? Also, once I engage the cat can I cut the primary air down right away?
I believe the manual says, and I think this forum will also generally agree, you should engage cat as soon as that temp gauge shows it in the active range (just touching on active, doesn't need to reach the middle or anything).
And yes, i believe once the cat is engaged, and you're happy with your flue temps, you can start dialing back the air intake. That is what i have been doing. sometimes i actually cut the air back a bit before the cat is even engaged - but i think i have excessive draft. sometimes for me, dialing the air back a bit actually accelerates the rate of temperature increase on the cat gauge (that is, get's it up to temp faster). When i start dialing back the air a bit I'll start getting more secondaries and more heat inside the stove. But again, this may be specific to my draft/setup.
 

neverstop

Member
Oct 11, 2020
123
new hampshire
Catalysts operate between 500-1600º. You should be able to engage it as soon as the cat gauge gets into the active (silver) zone.

I wouldn't trust the old Rutland thermometer to be accurate. What is the temp if you swap out the other thermometer at that location?

PS: The black thermometer is a flue thermometer. The scales (Best Operation/Too Hot) are for single-wall stove pipe. You are ok running the stove in the 5-700º range.
I swapped the thermometers on a different burn and didn't see a difference; however the cat thermometer also didn't straddle the top of its active range on this burn
I believe the manual says, and I think this forum will also generally agree, you should engage cat as soon as that temp gauge shows it in the active range (just touching on active, doesn't need to reach the middle or anything).
And yes, i believe once the cat is engaged, and you're happy with your flue temps, you can start dialing back the air intake. That is what i have been doing. sometimes i actually cut the air back a bit before the cat is even engaged - but i think i have excessive draft. sometimes for me, dialing the air back a bit actually accelerates the rate of temperature increase on the cat gauge (that is, get's it up to temp faster). When i start dialing back the air a bit I'll start getting more secondaries and more heat inside the stove. But again, this may be specific to my draft/setup.
Yes I've noticed more secondaries as the air is dialed back, and maybe I'm waiting too long to engage the cats. This has all been with small top down cold start loads. So maybe 1/4 loaded firebox. I'd like to get the technique down prior to reloading with a full load as I don't want to have a run-away stove situation.
 

tabner

Feeling the Heat
Jan 17, 2019
261
Eastern CT
I swapped the thermometers on a different burn and didn't see a difference; however the cat thermometer also didn't straddle the top of its active range on this burn

Yes I've noticed more secondaries as the air is dialed back, and maybe I'm waiting too long to engage the cats. This has all been with small top down cold start loads. So maybe 1/4 loaded firebox. I'd like to get the technique down prior to reloading with a full load as I don't want to have a run-away stove situation.
obviously i can't guarantee anything since everyone's flue and draft and fuel setup is different. But i have basically the same firebox and air control and cat setup as you (i believe) and i have a 27 foot chimney with high draft, and i've never really come close to overfiring, including on hot reloads. I think the air shuts down pretty tight on these stoves. And i do have a flue damper as well just in case.
 

begreen

Mooderator
Staff member
Nov 18, 2005
92,752
South Puget Sound, WA
Try this with a larger load of wood, say half full. Top down start the fire. Air wide open and the door slightly ajar. Latch the door when the fire start to burn the top wood with some vigor. When the cat thermometer is solidly in the active zone, close the bypass. Leave the air control wide open. 5 or 10 minutes later, when the wood is burning well, close the air down 50% or until the flames slow down and start to get lazier. Wait 5 or 10 minutes for the flames to recover some strength and close down the air some more until the flames get lazy again. Repeat the cycle again if necessary.
 

tabner

Feeling the Heat
Jan 17, 2019
261
Eastern CT
Try this with a larger load of wood, say half full. Top down start the fire. Air wide open and the door slightly ajar. Latch the door when the fire start to burn the top wood with some vigor. When the cat thermometer is solidly in the active zone, close the bypass. Leave the air control wide open. 5 or 10 minutes later, when the wood is burning well, close the air down 50% or until the flames slow down and start to get lazier. Wait 5 or 10 minutes for the flames to recover some strength and close down the air some more until the flames get lazy again. Repeat the cycle again if necessary.
Apologies if i hijack the thread a bit, but since it's same firebox, i hope it's pertinent. I was getting really comfortable with my stove until i had a series of bad backpuffs that have stressed me out a bit. Is this "closing down in stages" the key to avoiding that? Also, would shutting down sooner actually be better? (i had been trying to shut down a little later thinking i needed to get more of the aggressive offgassing over with while wide open, but now i'm thinking that ignites too much of the load and then when you do shut down, you've got too much wood offgassing?) And with a flue damper, would you suggest relying on the Air intake control mostly, and only starting to close the flue damper once/if i have fully utilized the air control?
 

begreen

Mooderator
Staff member
Nov 18, 2005
92,752
South Puget Sound, WA
Backpuffing happens when the flame goes out while the wood is still actively outgassing. This fills the firebox with smoke (wood gases), when a flame erupts, it ignites these unburnt gases with a small explosion (backpuff). This can be disconcerting.

The problem is generally a sign of partially seasoned wood or insufficient draft, but it can occur by shutting down the air too quickly. If the wood is suspect then the fire will need more air.
 
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neverstop

Member
Oct 11, 2020
123
new hampshire
Try this with a larger load of wood, say half full. Top down start the fire. Air wide open and the door slightly ajar. Latch the door when the fire start to burn the top wood with some vigor. When the cat thermometer is solidly in the active zone, close the bypass. Leave the air control wide open. 5 or 10 minutes later, when the wood is burning well, close the air down 50% or until the flames slow down and start to get lazier. Wait 5 or 10 minutes for the flames to recover some strength and close down the air some more until the flames get lazy again. Repeat the cycle again if necessary.
20211129_202157.jpg
Followed your suggestion. This is with the primary air on the lowest setting, and cat engaged. Went like this for 15 minutes then flames died and cats are glowing

Stove top is almost 500, been steadily climbing. Above the cats its 435 and slowly climbing. Cat thermometer is in the middle of the active range.

Your right the Rutland is not reading correctly.
 

begreen

Mooderator
Staff member
Nov 18, 2005
92,752
South Puget Sound, WA
That's more like it. Looks good.
 

neverstop

Member
Oct 11, 2020
123
new hampshire
That's more like it. Looks good.
Stove back puffed 10 minutes after flames died. I did close the window after startup. So I cracked the window again and opened the primary a bit. Secondaries aren't firing like the last pic anymore.
 

begreen

Mooderator
Staff member
Nov 18, 2005
92,752
South Puget Sound, WA
Next time try closing down the air part way, say down to 25% so that their is some flame. If opening a nearby window makes a notable difference, the stove needs and outside air connection.
 

neverstop

Member
Oct 11, 2020
123
new hampshire
Next time try closing down the air part way, say down to 25% so that their is some flame. If opening a nearby window makes a notable difference, the stove needs and outside air connection.
I turned the air down all of the way because it seemed like temps were going to continue to rise above 500 uncontrolled even though it was at ~25% open. But I suppose it was an unwarranted worry given I was looking at my Rutland gauge which is reading high. I have an IR gun on order.
On some of my previous cat stoves I had to leave enough air going to the fire to keep a small flame going to prevent back puffs till the wood had outgassed enough to turn the primary air down more. You will get the hang of it after a while.
Is this a sign of insufficient draft or is this simply rushing the shut down process? How do people load the stove, set the air and then leave for work? Is this an hr long process?
 

begreen

Mooderator
Staff member
Nov 18, 2005
92,752
South Puget Sound, WA
How do people load the stove, set the air and then leave for work? Is this an hr long process?
Note that there are very few people reporting here on this stove. It's a new design. All we can speak of is that which is typical, for our stove(s). Wood burning is not a formula or one shoe fits all exercise. Every stove is going to be influenced by things that are peculiar to its installation, fuel, weather, and operator. There are so many variables within those 4 parameters that at best we can only provide general advice. By the end of the season, you will be one of the veterans telling us how the stove runs, in your home. With better instrumentation, you will have greater confidence in exploring the range of capabilities of the stove.
 
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neverstop

Member
Oct 11, 2020
123
new hampshire
Note that there are very few people reporting here on this stove. It's a new design. All we can speak of is that which is typical, for our stove(s). Wood burning is not a formula or one shoe fits all exercise. Every stove is going to be influenced by things that are peculiar to its installation, fuel, weather, and operator. There are so many variables within those 4 parameters that at best we can only provide general advice. By the end of the season, you will be one of the veterans telling us how the stove runs, in your home. With better instrumentation, you will have greater confidence in exploring the range of capabilities of the stove.
understood, my question was more general. I was wondering how long people spend tending to the fire prior to leaving for work
If you rush it for you absolutely get back puffs, but it could be draft related as well, what is your chimney setup?
~17ft exterior chimney with clay tiles, SS liner (not insulated), rear exit flue setup probably close to 36" horizontal run from stove to the liner tee.
 

mellow

Resident Stove Connoisseur
Jan 19, 2008
5,362
Salisbury, MD
~17ft exterior chimney with clay tiles, SS liner (not insulated), rear exit flue setup probably close to 36" horizontal run from stove to the liner tee.

That isn't helping any, should have installed an insulated liner, especially with a stove that likes to burn low and slow so you have good draft. That 17ft with the 90 off a rear vent stove is a draft killer, now you are adding the heat robbing clay tiles to the mix.

I would see if you can pull the liner and insulate it and then possibly install another couple feet of chimney above your crown.
 

begreen

Mooderator
Staff member
Nov 18, 2005
92,752
South Puget Sound, WA
understood, my question was more general. I was wondering how long people spend tending to the fire prior to leaving for work
It will depend on the stove design, wood, loading skill etc. It also depends on whether it is a cold start or a hot one and how large a coal bed there is. On a good day, this could be 30 minutes for our stove. However, in the beginning, I would allow 45-60 minutes because sometimes things don't work as well as planned.
 

neverstop

Member
Oct 11, 2020
123
new hampshire
That isn't helping any, should have installed an insulated liner, especially with a stove that likes to burn low and slow so you have good draft. That 17ft with the 90 off a rear vent stove is a draft killer, now you are adding the heat robbing clay tiles to the mix.

I would see if you can pull the liner and insulate it and then possibly install another couple feet of chimney above your crown.
yes, that was ignorance on my part. I'm in the process of insulating it, and most likely adding 4ft or so to it
 
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Highbeam

Minister of Fire
Dec 28, 2006
19,679
Mt. Rainier Foothills, WA
understood, my question was more general. I was wondering how long people spend tending to the fire prior to leaving for work

No time. I spend a brief moment basking in the heat produced from the fire I loaded the night before which will still be making heat and keeping the house warm when I return home from work.

If your stove is a hearthstone and performs per the marketing brochure, you should be able to do the same right?
 

neverstop

Member
Oct 11, 2020
123
new hampshire
No time. I spend a brief moment basking in the heat produced from the fire I loaded the night before which will still be making heat and keeping the house warm when I return home from work.

If your stove is a hearthstone and performs per the marketing brochure, you should be able to do the same right?
Still getting used to how the stove operates vs. my old VC Vigilant. So haven't done more than a few splits. That lasted 5 hrs or so though
 
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