Let the big cat eat! Buck 91 up and running. Advice, tricks and tips welcome...

Everything on the install went pretty smoothly. Here's the link to that thread, if anyone is interested:

http://www.hearth.com/talk/threads/the-buck-stops-here-91-bay-heater-install-under-way.92228/

One Saturday, I decided to take the stove over to my MIL's and see if I could recruit a few guys to help me move it from the trailer to the hearth. If not, I was going to leave it there on the trailer. I stopped on my way out and talked to my wife's cousin, who told me that three other beefy men cousins were in town for the day and would be passing by my MIL's house shortly. Pretty easy getting the stove in with that many guys, and the door off and bricks and combustor/frame assembly out (Had taken the combustor out and given it the vinegar/water simmer and rinse.) maflake, neighbor of mine and fellow Buck 91 operator, got to save his back for another day. We've got some wet Red Oak to haul out at his place, so he'll need the healthiest back he can muster.

I was going to put a Roxul block-off plate of sorts up where the smoke chamber narrowed down, but spaced out and forgot to do it before we slid the stove into the fireplace. Maybe later I can do that...

I had to lift the liner with a floor jack and re-clamp it up out of the way to have the necessary clearance to get the stove in.



Begreen suggested in one thread to slide the stove in using a sheet metal skid plate, and that worked great. My nephew and I slid it in and then he guided the flue collar/liner as I lowered it from the top.

I still need to extend the hearth, and I'm a few inches short on mantle clearance. Heat moves out of the two doorways pretty well now but it remains to be seen if fans are needed when it gets colder...I think they will be.



Can't see it too well in this pic but the 36" wood hoop looks pretty good.



Stove temp 500; Cat probe 1500.



I started cautiously with a small fire, as other operators of this stove have said that the combustor temp can go over the 1800 max suggested in the manual to prolong the life of the cat, which is already four years old. That went well so I built a bigger fire the next time. I must have had too much small stuff or the coal bed was too much under the load, and the combustor got up to around 1750. The liner must have expanded as well because some creo chunks left over from the previous slammer install started falling on top of the stove and I had to keep brushing them off to prevent too much smoke in the stove room. Before the stove went in I had gotten as much of the loose stuff as I could with the liner in my way, but not all of it apparently. I think all the stuff that was going to fall is gone; On subsequent firings the amount of debris falling eventually tailed off to nothing. I installed the surround (which was a bit harder to do since the stove was already in place.) I have the gold spring handles and gold trim that goes around the front of the ash lip, which I've yet to install. I guess I've got to remove the ash lip to slip the trim on. I also want to get a corded hand-held vac to keep the area neat, and clean off the ash lip and door gasket, which seems to always get a little blow-back ash on it no matter how slowly I open the door.

Over the last few weeks, I've been burning one or two loads a day in the stove, depending on how cold it it outside. It takes a pretty lively fire for a while to get the combustor probe up to the 700-900 recommended in the manual before closing the bypass. I've got some soft Maple and Pine that I'm using to get it up to temp but not leave big chunks or a big coal bed. I then rake the coals forward and put in a full load. It's hard to learn the stove when I'm not there to observe the full burn cycle. I've had my MIL call me a few times to update me on how a load is doing and get me the stove and combustor temps. A few nights ago the combustor was at 1650 when I left and I had her call me an hour later. Combustor was a 1800. I had already cut the air back pretty much, and I had her cut it all the way to get the load to slow down, and had her turn up the fan, which seems to help. I think I had the load burning for too long before cutting the air back, and too much of the load got involved. At this point, I'm wondering how I will be able to get a higher burn rate when it's cold out, yet not have the cat get too hot.

The stove was burning more on the left side than the right and the glass was a bit dirty in the lower right corner (as you can see in the above pic.) I thought I might have a blockage in the right primary air channel. I've got a mechanic's grabber tool, a flex cable housing with a claw on the end, that I ran up the right intake but it was clear. Then I thought "Hey, the ash drop is on the left side..." Sure enough, the gasket may had a little gap where the ends come together. Last night I put on a new gasket. When I lit the stove I saw immediate improvement. The load was actually burning on the right side, something I hadn't seen before. I left the air open a little and had my MIL call me with a temp report a couple hours after I started the load; Had 350/1500. I stopped by this AM to see how the load was doing and was pleasantly surprised to find room temps a couple of degrees higher and more fuel than usual left in the stove. I think the ash pan gasket leak caused the load to burn up more quickly even if the primary air was cut all the way. So I guess the load is burning more slowly, even though I gave it some air last night, and the heat output is higher in the morning due to the extended burn. It'll be nice for her to wake up to a warmer house. I'm hoping that getting more control over the air will also reduce the chances of the combustor going too high.

The ash pan doesn't lock into place, there's just a piece of spring steel exerting pressure on the side of the pan to hold it in place. I like the ash drop...pretty easy to use. I've found that I need to run a poker behind the hinge and clean off the top of the lid to get it to open easily. Ash pan holds several loads worth. The back of the pan has no wall, so it will plow through any ash or coals that have spilled in the cavity. This feature also makes it easy to just slide the ashes out of the end of the pan and into the bucket; Much less dust than when you have to dump the pan upside down to empty it.

Soooo, Buck 91 owners...

--What have you found to be the quickest way to get this big chunk of steel up to temp from a cold start? Wide open primary and shotgun air, or certain ratios of each at different points in the warm-up burn? I've also tried cutting the air back as much as possible while still keeping the flames pretty big to keep more heat in the box, but the jury for me is still out on what is the quickest way. Once when I forgot to open the bypass, the cat probe got up to temp real fast just burning a couple of warm-up splits...but I really don't like running any unburned smoke through a cat... I've noticed too that after I close the bypass, the cat probe has to be up around 1000 before it really starts burning all the smoke. Maybe I'm giving it too much air at that point...

--How do you run this stove when you need a lot of heat? Air more open and flames in the box? Do you still get a clean burn, and does the cat get up around the dreaded 1800?

--Does the cat temp ever go to the moon on you? What do you do then? How do you prevent it from going too high in the first place?

--Ever load E/W? What did you find vs. N/S?

--Do you use different fan speeds? If so, what's your thinking on this?

--Does your glass stay pretty clean? My right side glass got dirty until I fixed the ash pan gasket. This AM, both sided were a little dirty but not like the right side was before. Is slightly dirty glass on a low burn something I'll just have to live with?

Any other knowledge about running this stove from seasoned operators would be most welcome.

It is pretty close to my bay 52, just bigger. I have found doing a load of N/S on the bottom then loading E/W on top of that keeps the fire going better when I cut the air way down. The glass on my door darkens, the air wash on these stoves is not the greatest when you have it set to hardly any air coming in. I run my fan on low due to how loud it is while we are in the room, when I go to bed I put it on high for an overnight burn. Mine takes a little while to get the cat up to temp (15-20 minutes from cold start), I burn N/S to get it up to temp quicker, the bay 52 has a startup air slide below the door, that helps to get the fire going. If the cat on mine goes above 1700 I will put the fan on high even if we are in the room just to play it safe. I haven't had to run mine hard yet so I can't answer that question. But in theory with a full load and a little air it should have the cat pegged.

I follow the manual instructions. It tells you when to shut down the air and how far to shut it down and when to close the bypass. I am just using this guide until I see if I can find a more efficient way. I have only been above 1800 one time.

Good looking set up you got there Woody, Not much help here on tips, but that thing looks big enough to make them candles lean when you crank it up Really like the big glass view and hearth background, enjoy, Todd 2

I'm not a Buck 91 burner, but in case you've missed the threads, consensus on other cat stoves seems to be that the more flame you run in the firebox, the less smoke there is for the cat to eat. . .cat and stove top get cooler, all other sides of the stove get warmer; so more total heat output, but less heat from the cat when running the stove hard. Basically, you burn the smoke in the firebox(as flame), or you burn it in the cat. YMMV with the Buck, but I don't know why it would be radically different from other cats.

You're a good SIL. Nice install, and good on ya for making this happen for her!

Yesterday my SIL was over there and added wood in the early afternoon. There was still a huge coal bed in the stove so I could only add one layer of splits. I wasn't as worried about the big coal bed, since I had stemmed the air leak at the ash pan gasket. I returned an hour later and the cat was a little over 1600. I really didn't want to see it go much higher than that. There are two inlets for air wash primary air, and the right-side air slider is a long bar with two plates attached that cover the air inlets as the slider is moved. I saw that with the air all the way closed, the plated didn't fit tightly against the openings, allowing some air to still enter the stove. I grabbed a little wood chip and stuck it between the end of the slider and the ash lip, which pushed the plates up tighter against the openings. I turned the blower on 'high' and the cat temp seemed to level off so I called it a day. When I came back this AM there was still a fairly large coal bed left. That load had burned considerably slower than I was used to. What I may do is to put a couple of washers between the slider bar and the plates, which would allow me to cut back the air more, if need be.
There is still some air coming in at the ash drop lid; Appears to be at the hinge area which would make sense as the lid probably fits the rest of the opening fairly tightly. I could seal that area with high-temp silicone, but I really don't want to give up the ash drop. I could also put a large flat split over the lid to disperse the air so it would not be concentrated in one area. Or I could cut a steel plate maybe 6x8" that would do the same thing, but that sounds like it would be a hassle to mess with every time you want to drop ashes. I could make an effort to clear the coal bed away from lid further when loading. Hmmm, maybe I could glue a piece of gasket inside the ash drop opening, or to the lid, that would seal off the hinge area...

Yep, gettin' 'er done so far, but the coldest it's been so far is mid 20s...
The only Buck cat 6" I see on the website is the 20. They claim 1.9 cu.ft. on that. Can't recall what your square footage is in your "joint." They claim 4.4 for the 91 but below the cat heat shield it's a bit over 2.5 that you can actually pack with wood. Either way, it seems as if it's capable of tossing major heat. As far as the stove itself, it's a heavy-duty piece. I think the top of the box is 5/16". This bad@ss is a chunk of iron, for sure. There are some other (older?) cat models listed on the "EPA certified" page, so maybe some of those are 6" as well...

Yeah, I'm just playing with it at this point to try to find better, quicker ways to get cat temp, etc. When I go over there, I don't want to be messing around real long. Need to get back home to load my stove.
On my small ramp-up fires I've been using several 2" splits to get big flame but still leave plenty of room for the main load. As the ramp up load burns down and starts to coal, I might try cheating and engaging the cat even though the probe is only at 600 or so. Maybe that will get the cat temp up around 900 quickly, without running too much unburned smoke through the cat. The reason I don't want to do that is so I don't put any creo in the cat which will later burn and accelerate the masking of the cat with ash. It is some work to get the cat out of this stove, not like the Fireview where I lift the lid and remove...about a five-second job. But as it is, if I have 700 on the probe and put in a full load and engage, it takes a while to get up above 900, where it seems the cat is starting to really reduce the visible smoke out of the stack. That's got to end up masking the cat with burnt creo ash as much as the method I want to try, I'd think?

Yeah, that's basically how it is with the Fireview. But it seems like with the Buck, more flame can increase the cat temp. I'm not really sure...still learning at this point. Not being there to see a full burn, make adjustments etc. is slowing down the learning curve quite a bit.

Thanks! She's been good to us as well, so I'm glad to be able to do it. It also supplies an outlet for my inner stove nerd, so I benefit as well...and my obsessive wood hoarding over the last couple years now looks to the family like it made sense, after all. I hope her next utility bill is like $10 or something; That will really make her smile.

Maybe the cat probe is being heated up, but not by the cat?

The manual doesn't call for the Cat temp to be any certain temperature. It states once you have a good fire to close the bypass. Before I started doing what the manual said I burnt up an entire load waiting on the Cat temp that never happened, because the heat goes straight up the chimney in the back and never heated the Cat. When I hit the bypass the cat temp is usually around 200 but then rises quickly to the 1000 -1200 range.

Not sure but maybe when there are flames, that heat hits the cat and the probe. In that case the cat would be getting hotter also. I can't compare it to the Fv because the tip of its probe isn't over the cat. I need to get a longer probe if it's availabel, or maybe digital probe...

The online manual and my printed manual say to get the probe to 700-900*. Tonight I had about 700 on the probe and engaged. With a little flame in the box the probe didn't climb very quickly. When I cut the air and snuffed the flame, the cat evidently started burning the smoke because the probe then rose a lot quicker (for the reason ddddddden stated above.) I don't know why they want that 700-900 probe reading if the cat is going to start burning quickly from as low as 200...maybe to minimize creo deposits becoming ash and masking the cat? Or maybe the cat can stall, but I haven't seen that yet with the higher probe temps I've been waiting for. I might contact them to see if I can get more info.

Page 5 here:
http://www.buckstove.com/buckfiles/manuals/Buck-Stove-Model-91-Manual-(Rev-10102008).pdf

I was going by page 21. How to build a fire.

8. Once your fire is burning well, close the bypass damper completely (push in). Gradually close the primary air
controls (push in). You will have to experiment with the primary air controls to accommodate your draft. If
you close them too soon, your fire may die down too quickly and go out. Close them gradually, a little at a
time, until you can close completely.

Well, I will just have to keep playing with it.

Todd talked to someone at. . .I think it was Condar. IIRC, they said that the probe tip has to be within 1/4" of the cat to get an accurate reading. Maybe send him a msg. . .
You could use a thermocouple and log the output to a laptop; then you wouldn't have to be there to know how the stove was burning.

I don't know either, but I'm curious to hear their explanation.

Whoa! I was laboring under a misconception regarding combustion air to the stove. Pretty sure that the right-side slider feeds air to both channels in the top of the fire box; The air wash channel, and the second one across the middle in the top of the fire box. The left slider "shot gun air" enters in the front center just below the door opening. That will be handy for starting a mini-blaze with small stuff in the front when starting a cold stove. That air enters below the cat heat shield so might be useful to heat up the cat area faster.
This AM I just put in a few chunks and uglies. I closed the bypass around 600 and snuffed the flame; Cat got up to 900 pretty quickly. That little load should get me to this afternoon, when I'm going over to clean the glass...and perform a little experiment. Then I'm gonna load up and try for a low 16-hr burn.

Yeah, that would be very helpful. So would a web cam but she has no internet over there.
"Log" the output...funny stuff, den.

Yeah, why do they want 700-900 when others (Fv, e.g.) say 250 stove top equal 500 internal, and that is enough to light off the cat. I guess the stove construction could be a variable but I'm pretty sure the cats are the same or very similar.

Do you all do anything about those bay windows? I cleaned mine when I bought it and they have been black ever since. I could care less if they are clean, but the wife is like, "why can't I see through those"?

Our Buck 80 has secondary air supply channels that feed from the front, bottom corners. If the corner trim piece is removed, one can see the channel iron welded to the outside of the firebox that angles up to where it enters the firebox and feeds air behind the catalyst chamber. There is no user control for these secondary air inlets. I've seen jets of flame coming out of the holes in that secondary during really hot fires. I wouldn't be surprised if the Model 91 uses a similar setup.

Yeah, I figured that you had to have the 700-900 on the probe before closing the bypass on a new load. Usually, by the time I got the wood loaded, the temp had dropped down. Then the combustor would never take off because I was cutting the air back too much. What I do now if I have a decent coal bed is to throw on a couple of small kindling splits and burn those pretty hot, using some shot gun air with air wash air. When those splits are pretty well burned up but still flaming, I'll close the bypass and get the cat cooking and the probe temp up to 900 or so. Then I load the stove with the coals pushed into the middle N/S. I make sure that there are no coals under the splits that I load on the left side, so that the ash drop air doesn't burn up those splits until later. I think that is what was happening when I got the 1800 cat temps; Too much wood gassing at the beginning. So I've got the coals in the middle and not under the splits on the sides. Then I toss a few smaller splits on the coals in the middle, close the bypass and get some decent flame going in the middle. This seems to bring the cat probe up quickly, even if the cat probe started at only 550-600, and I can see the cat start to glow in maybe ten minutes (not like the Fireview, where you close the bypass and the cat is glowing immediately and you can cut the air to zero if you want.) But re-reading the section you reference, it says "gradually close the primary air controls." I guess my reading comprehension skills need more work.
I like to have the probe as high as possible to minimize the amount of time that unburned smoke is going through the cat. I don't think the cat has gone high since I started loading this way. Hard to say for sure since I'm not there to watch the entire burn. I have stopped back several times after an hour or two and the cat hasn't been too hot, so I think this method is working.
My cat temps won't zoom from 200 up to 1000 like yours apparently does; It would take me a good while to cover that distance. Your combustor isn't new either, but maybe mine is not working as well as yours. I would toss a new one in there...if it wasn't $285.

I'd certainly like to hear from other operators detailing their start-up/reload procedures...

I guess the air wash doesn't hit those bay windows. I don't bother with cleaning 'em. It would be cool to be able to see the flame through those...

Sounds like the 91 has a different setup. I believe that the air is coming into my stove as stated in my post that you quoted. I think that both air wash air and shot gun air would be considered 'primary' air but I'm sure that smoke can ignite up in the top of the stove and look a bit like secondary flames. I have on occasion seen some flame through the gap between the cat heat shield and the air wash channel, or through the holes in the back of the air wash channel, visible through the front air wash mesh. I haven't had the sheet metal trim off to actually verify where the air channels go from the front bottom intakes. It's intuitive that the shot gun air would come out right above where the inlet is, in the middle underneath, and you can see this air blowing on the coals when you open it up.

Looks nice.

Right, you have to keep playing with it until you finally figure out that you have to use part of what they say on page 21 and part of what they say on page 5. I've gotten that far, now I've trying to get a better feel for the combination of flame and air, at different stages of the ramp-up, that will get the temp up and cat lit off the quickest. I can pretty much have it cruising in about half an hour if I have some coals to work with, a bit longer if I'm starting cold. Like I said, the jury is still out on this cat. It may be a bit tired, judging from how fast you say yours will take off from low temps...

page 5
ACHIEVING CATALYTIC LIGHT-OFF
The temperature in the stove and the gases entering the combustor must be raised to between 700 F to 900 F for
catalytic activity to be initiated. The temperature can be determined by the Catalyst Monitor Probe. During the
start up of a cold stove a medium to high firing rate must be maintained for about 20 minutes. This can be
achieved by starting the fire with dry kindling, paper, and small split wood. Have the Bypass Damper fully open
(pulled out). This ensures that the stove, catalyst, and fuel are all stabilized at proper operating temperatures.
Even though it is possible (and likely) to have gas temperatures reach 600 F within two to three minutes after a
fire is started, if the fire is allowed to die down immediately it may go out or the combustor may stop working.
Once the combustor starts working, heat generated in it by burning the smoke will keep it working.

ACHIEVING CATALYTIC LIGHT-OFF WHEN REFUELING
During the refueling and rekindling of a cool fire, or a fire that has burned down to the charcoal phase, operate the
stove at a medium to high firing rate for about 10 minutes to ensure that the catalyst reaches approximately 800
F.

This AM I tossed in a load of soft Maple on a pretty big coal bed. I have to burn the load for a while to get the cat lit off, and I got a bit of a "goer" this time as the cat headed for 1500. I had to leave but stopped back in about an hour and it had leveled off a little over 1600. I'm starting to get more confident that if I load this stove right I can keep the cat temp from taking off. I just have to take a little more care with wood that tends to burn faster; Big splits of Oak, Ash, Hickory seem to burn in a very controlled manner...

How long is it taking you folks to get above 1000 on a reload with a coal bed, and from a cold start?

Cold start, takes atleast 45 minutes to get to 1000 on the cat. I have to burn up the starting wood quite a bit before I close the damper at around 600 on the cat probe (30 minutes), then it takes it another 15 minutes to go over 1000.

I'm late to this thread but glad to see some other Buck 91 users here. I'm on my third year with this stove but the first year doesn't really count because I had a 'slammer' install and terrible (read unseasoned) wood. Last year I installed a liner and block off plate and my wood was much better. This year I have 2 year old oak and sweet gum with a bit of hickory as well. This year I feel like I'm finally learning what the stove will do and how to run it effectively.

First off let me say that I don't wait for the cat probe to read 7-800 before I engage it. I engage at about 4-500 regularly and it takes off from there. If it is a cold start, it probably takes about 45 min to get the cat to 1000 but if I reload on a hot coal bed with the cat reading 4-500 still, I open the door, load it up, close it and immediately engage the cat again even if it's around 400. I open the air full blast (including the doghouse). I let er rip until the cat is at about 1000 (about 10-15 min) then shut it down 1/2 way or maybe a little more. Once the cat gets to 1500 I shut it down to just a crack past closed and then a few minutes later close it all the way down. It will then run at 1500 to 1700 for a couple hours, depending on the size of the load, and start down from there. If I load it up about 1/2 to 3/4 with good oak, I get about 8 hours of usable heat and if I load it to the gills I can get 12-14. When the cat is in the 1500 range my stove temp thermometer on the front just like yours is in the 600 range. I don't think we can compare stove top temps with what a lot of people talk about here because of the air sheathing around and above it which keeps the temp of the metal lower than one without a blower.

Lots of good info and questions here in this thread and I'll chew on some of it a bit more and get back.

Glad to hear I'm not the only one who finds the side bay glass completely useless.

I loaded up the stove this morning at 8 with about 3/4 load of sweetgum and 1 large oak split. It got warm this afternoon and so I didn't touch the stove all day and this was at 7 this evening. So 11 hours and still putting out usable heat. I have the cat probe marked and the marker painted white. It helps me see what is going on at a glance when the light is low. You can see I have the 400 marked and when it gets to there, I usually engage the cat. I have heard people talk about 'stalled' cats but don't really know what that means. Even though I engage a lot lower than the book says to, I've never not have it take off and head up quickly.

My cats came with the stove and I have no idea of the history since I bought it used from a foreclosed house. I am in my third year on them and they seem to be doing great. Here is a picture of my stove. I chose to not use the surround as I thought I would get more heat out of it. I painted the inside of the fireplace black and I like the look of it. Kind of a freestanding stove in the fireplace rather than the classic insert look.

WoodpileOCD: I am jealous you are able to have wood inside this year, this is the first year I have had to keep the wood outside on the porch and bring in a load at a time, we have been having huge issues with spiders this year coming in on the wood (kids and wife are not to keen on them).

It is pretty cool how the Appalachian stoves are pretty close to the Bucks in terms of operation, probably can say the same for the Stoll 1500,2500 stoves.

Let the fire go out last night so decided to document the cold start this morning. Here it is

8:25 start w/ 6 small to medium splits and 4 pieces of split 2x4 kindling (and a 1/8 super cedar)
8:42 cat at 400 so engaged. Stovetop at 200
8:48 cat at 800 ST at 250
8:51 cat at 1000 ST 300 air to 1/2
8:56 cat at 1200 ST 375 air to 1/4
9:03 cat at 1400 ST 450 air just cracked
9:10 cat still at 1400 ST 550 air shut all the way down

Never got above 1400 but I didn't have that much wood in it either. You can see that the cat takes right off when it is engaged at 400 which tells me its eating smoke right away. I've watched it start to move almost as soon as I engage it at this temp.