UPDATE: Dealing with Excessive Catalytic Tempuratures

Gridlock · Oct 14, 2010

It got fairly cold last night, so loaded up the stove fully for the first time this season. In the off-season, I had the flue switched from a 6 inch flex pipe, to 8 inch stainless which has made a huge difference in draft and seemed to correct all the back-puffing issues last season.

The problem is with high CAT temperatures on a full load. I have the Condar digital guage which read a high of 1900 degrees at one point about 30 minutes after closing the damper and engaging the CAT. Aside from that, the stove ran great; I woke up with the stove top temperature still at 400 degrees and the CAT at 600; that's after a 9 hour burn. The moisture content of the wood is in the 15 - 20% range.

The firebox still had a burning log and lots of hot coals when I packed it for the night. I let it burn for about 15 minutes fully open, then engaged the CAT and reduced the air intake to about 1/4. The CAT temperature quicly rose until it hit 1900 degrees, then dropped back down to normal levels.

Is there a way to prevent this with a full load (partial loads don't present this problem). Should I have:

1) Not burned the full load for 10-15 minutes before closing the damper? This makes sense to me as it seems that all that charred wood produces a ton of smoke. Maybe enaging the CAT sooner before all the wood is charred will cause the CAT to process less smoke from all that burning wood.

2) Reduced the air control more slowly allowing more of the smoke to burn in the main firebox?

3) Load it will less wood?

4) Something else?

Which leads me to my next question: If I didn't have the CAT temperature guage, I'd have no idea (aside from some metal expansion popping noises) that it was running so hot, as it is heating wonderfully and otherwise working great; do most of you with CAT stoves have a guage on the CAT, and if not, how do you know that your CAT is operating within the correct range?

Backwoods Savage · Oct 14, 2010

We do not have a probe on our cat but just go by stove top temperature. We certainly know when the cat is working because the temperature goes up rather quickly. The few times we have had the stove go to or above 700 we have simply bypassed the cat for just a very few minutes and then re-engage and all was well.

As to the idea of less than 10-15 minutes, we do that but not on a full load. The only reason we do it is because our wood is super dry. If the wood were less than 3 years in the stack I probably would not try that. I do watch the wood and much prefer it to be charred good before turning the cat on.

So, no, I probably would not recommend turning the cat on before 10 minutes as a minimum unless it is only a partial load.....like maybe 2 small splits.

Reducing the air slowly can be good. Most times we can not leave our draft fully open for 10 minutes or that thing would be roaring like a lion. We usually dial it down to 1/2 or less as soon as we have good flame.

Loading with less wood will give you shorter burns and that is perhaps not what you want.

Something else? Yes, the fuel. What is it? How big are the splits? How long has it been seasoned?

Do you follow the same rules for every fire? Personally I do not. It all depends upon the fuel, the draft and the fire. Rules are really guidelines and not set in stone.

Naturally one also wants to check and double check for any and all leaks. Is air getting into the stove from some place other than the draft channel? Have you checked all gaskets?

Good luck.

Gridlock · Oct 14, 2010

Backwoods Savage said:
We do not have a probe on our cat but just go by stove top temperature. We certainly know when the cat is working because the temperature goes up rather quickly. The few times we have had the stove go to or above 700 we have simply bypassed the cat for just a very few minutes and then re-engage and all was well.

Yeah, but my stove top temperature was within normal operating range (500 degrees or so) while the CAT temperatore was 1900, so stovetop temp is not a good indication of CAT temperature.

Backwoods Savage said:
As to the idea of less than 10-15 minutes, we do that but not on a full load. The only reason we do it is because our wood is super dry. If the wood were less than 3 years in the stack I probably would not try that. I do watch the wood and much prefer it to be charred good before turning the cat on.

So, no, I probably would not recommend turning the cat on before 10 minutes as a minimum unless it is only a partial load.....like maybe 2 small splits.

Do you think that could somewhat depend on how hot the stove is already? Meaning, if you add a load of wood to a bed of coals that burned overnight, vs. adding the wood to a hot stove that still has some splits burning, which was my case last night. Because there was still burning wood in a hot stove, I wonder if I could have gotten away with engaging the CAT immediately without charring the entire load. I might try this anyway to see what happens.

Backwoods Savage said:
Reducing the air slowly can be good. Most times we can not leave our draft fully open for 10 minutes or that thing would be roaring like a lion. We usually dial it down to 1/2 or less as soon as we have good flame.

You dial it down BEFORE engaging the CAT or after?

Backwoods Savage said:
Loading with less wood will give you shorter burns and that is perhaps not what you want.

Definitely not!

Backwoods Savage said:
Something else? Yes, the fuel. What is it? How big are the splits? How long has it been seasoned?

To be honest, not quite sure. I get my wood from a neighbor who assures me it's seasoned, but we all know that the word is misused. I did measure some pieces with a moisture meter which generally reads in the 15-20% range, so I think it's Ok. I don't get any sizzling, and it does appear to burn well. The splits are fairly large in diameter, but not very long. It looks like the logs were split once, originally in the 5 to 7 inch diameter range.

Backwoods Savage said:
Do you follow the same rules for every fire? Personally I do not. It all depends upon the fuel, the draft and the fire. Rules are really guidelines and not set in stone.

More or less. I do make some adjustments, but am also a relatively new wood burner (this is my 3rd season).

Backwoods Savage said:
Naturally one also wants to check and double check for any and all leaks. Is air getting into the stove from some place other than the draft channel? Have you checked all gaskets?

I'll check again tonight. The stove was purchased new last December and only used for half of one season.

Backwoods Savage said:
Good luck.

Thanks, and thanks for all the information and ideas.

Backwoods Savage · Oct 14, 2010

Gridlock, I am not sure where your cat is located in your stove but in the Fireview it is near the front and we take the stove top temperature right in the center of the top, where the heat comes right out of the cat. That is perhaps why our stove top temperature is a reliable gauge for the cat.

On the engaging of the cat depending upon what is already in the stove, it is an interesting suggestion and someone else on this forum has approached me with a very similar idea and we'll likely kick that around for a bit along with contacting the company.

Yes, we do start dialing down before engaging the cat. Most don't, but we do many times; not always, but most times. For example, let's say I reload the stove when the stove top is 300 degrees. Should I then leave the cat engaged? I don't and have never tried it except by accident. That was quickly taken care of. But if I reload at 300 degrees and the flame starts up almost immediately (which it usually does) then depending on how the wood and flame look, I may engage after only 5 minutes but don't think I've ever went less than that. Also, when reloading in these temperatures, I will be turning down the draft usually within a minute or two at most. If the fuel was not as dry as we have it then I surely would not feel good in doing that.

And again, I'll state that the fuel you burn will get about 90% of the credit or the problem, whichever you have at the time. Most folks state they have wood but do not know what type of wood they have nor do they know how long it has been seasoned. MM will help but are still not the whole answer.

Good luck.

vvvv · Oct 14, 2010

try reloading with fewer coals under the wood? move them aside best u can

SolarAndWood · Oct 14, 2010

Does the spiking happen if you let the previous cycle finish down to coals and then do a full load? I do a full load every time and don't see that. But, the only thing in the box when I start is hot coals raked front center.

Todd · Oct 14, 2010

Occasional temp spikes over 1800 are normal and ok. You don't want to burn that hot for long periods. What does your flame look like when it was that hot? Sometimes the cat can get overload from a smouldering fire and rise quickly to the overfire range. This has happened to me a few times and like Dennis I usually bypass for a few minutes. If you keep some flame in the box the cat shouldn't take off on you, you may have turned it down too soon and too much.

Gridlock · Oct 14, 2010

Backwoods Savage said:
Gridlock, I am not sure where your cat is located in your stove but in the Fireview it is near the front and we take the stove top temperature right in the center of the top, where the heat comes right out of the cat. That is perhaps why our stove top temperature is a reliable gauge for the cat.

On the engaging of the cat depending upon what is already in the stove, it is an interesting suggestion and someone else on this forum has approached me with a very similar idea and we'll likely kick that around for a bit along with contacting the company.

Yes, we do start dialing down before engaging the cat. Most don't, but we do many times; not always, but most times. For example, let's say I reload the stove when the stove top is 300 degrees. Should I then leave the cat engaged? I don't and have never tried it except by accident. That was quickly taken care of. But if I reload at 300 degrees and the flame starts up almost immediately (which it usually does) then depending on how the wood and flame look, I may engage after only 5 minutes but don't think I've ever went less than that. Also, when reloading in these temperatures, I will be turning down the draft usually within a minute or two at most. If the fuel was not as dry as we have it then I surely would not feel good in doing that.

And again, I'll state that the fuel you burn will get about 90% of the credit or the problem, whichever you have at the time. Most folks state they have wood but do not know what type of wood they have nor do they know how long it has been seasoned. MM will help but are still not the whole answer.

Good luck.

The CAT in the VC Defiant is in the back of the stove. The smoke goes up toward the top of the stuff, then gets pulled down through the CAT then back to the bottom of the stove, then back of the sides. In this stove, the stovetop temperature is not a reliable indicator of CAT chamber temperature.

Thanks for the additional info. I do believe (based on my limted experience) that the wood is pretty good. It does start VERY easily, and seems to burn very well. I'll try some techniques as you have described to determine when to engage the CAT.

Thanks again.

Gridlock · Oct 14, 2010

~*~vvv~*~ said:
try reloading with fewer coals under the wood? move them aside best u can

Makes sense, but the problem is I can't always guarantee that, which depends on when I last loaded before reloading for the night. In other words, I started the stove when I got home from work, put a couple of splits in to last until just before going to sleep, but there was still a good amount of wood in the firebox, and I certainly didn't want to wait until the wood burned down before reloading and going to bed. I will try to move the burning wood and coals to the side though.

Thanks for the suggestion.

Gridlock · Oct 14, 2010

SolarAndWood said:
Does the spiking happen if you let the previous cycle finish down to coals and then do a full load? I do a full load every time and don't see that. But, the only thing in the box when I start is hot coals raked front center.

Similar to the last post, I can't always guarantee that when I go to bed for the night. I will try to move the coals and leftover burning wood to the front when I reload.

Thanks

Gridlock · Oct 14, 2010

Todd said:
Occasional temp spikes over 1800 are normal and ok. You don't want to burn that hot for long periods. What does your flame look like when it was that hot? Sometimes the cat can get overload from a smouldering fire and rise quickly to the overfire range. This has happened to me a few times and like Dennis I usually bypass for a few minutes. If you keep some flame in the box the cat shouldn't take off on you, you may have turned it down too soon and too much.

Is that right? I didn't realize that occassional spikes over 1800 were Ok. Is this mentioned in the manual for the Fireview? The manual for the Defiant only mentions that the normal operating range is between 1000 and 1700 degrees. Mine spiked to 1900, but then quickly went down to 1500 or so. Interestingly instead of opening the damper, I actually reduced the air intake completely which seemed to help lower the temperature. It just seemed that too much of the wood was burning producing a lot of smoke. Reducing the air control seemed to reduce the burning. I do think though that as you mentioned, I might have initially reduced the air too quickly.

Gridlock · Oct 15, 2010

UPDATE: Last night I tried what I mentioned earlier: I loaded up the stove completely before bed which still had lots of hot coals and a couple of burning splits, but did not char the wood very long (only a 3 or 4 minutes) before closing the damper; this worked GREAT! The CAT temperature rose to about 1150 degrees and stayed there for an hour until I went to bed. It did not spike. Since I didn't char all the new wood long, the load wasn't producing a huge amount of smoke, so the CAT wasn't being overloaded. The stovetop temperature was still around 400 degrees 9 hours later, and produced heat well into the afternoon.

Very cool!! :coolsmirk:

Backwoods Savage · Oct 16, 2010

That apparently is what your stove likes. Glad you have found the answer. My only question is why are you loading the stove at this time of the year? For example, our overnight temperature was around 32 degrees last night and we used 3 splits. We stayed very warm.

This is just a caution to the new wood burners. Most will tend to burn too much wood before January hits. It just does not take that much heat right now. Save your wood for when it is really needed.

mettauercat · Oct 23, 2010

Gridlock, just installed my new biscuit 1945 the last two weeks and just stsrting too learn its habbits and what works best. your problems are all too familar.I have been a loyal Vermont Castings fan for quite a while presently three in the house at this time. your Oct. 15th reply strikes me in that you went to bed after reloading and were pleased with your results of the cat not spiking. You had no way of knowing if the temps spiked or not. My large Winter Warm also reaches 1900F at times and I set and watch the digital too see how long it will stay there, If too long I open the damper for a while. It will also be running at normal temps for a while than all of a sudden spike to 1800- 1900 in the middle of a burn. So dont be surprised if you woke in the middle of the night and saw it at 1900 or possibly glowing. I love my stoves, but also accept the challenge they give me. I dare not to ever fully load my winter warm , and assume I will probably will do the same for the Defiant. It does only take a moment of neglect to ruin one of these stoves. I have rebuilt many and seen many ruined ones by carelessness. I'am a firm believer in burning during awake hours, and letting my programmable thermostat do what the rest. I do not want to come home to a house fire or be awaken by my smoke alarms. 3000 sq. ft. three story with two heat pumps and one of these with a back up propane furnace in Va. Just got a 80 gal. bill for the last two years. On a closing note, I had problems with my defiant running away, uncontrollable stove top temps over 500 degrees during start up fires. I solved this by plugging the two holes in the bottom of the ash belly with plugs similar to the ones used in electrical boxes. Vermont Castings chuckled and told me they were put in to help satisfy EPA. I did the same on my Winter Warm. It gave me the controll I needed. Feel free to call me, Larry @ 540 290- 9156

nate379 · Oct 23, 2010

It's pointless to have wood heat if you are only going to use it a few hours a day. I run mine 24/7 as do my folks. They have been heating for almost 30 years... so must be doing something right.

iceman · Oct 23, 2010

Backwoods Savage said:
That apparently is what your stove likes. Glad you have found the answer. My only question is why are you loading the stove at this time of the year? For example, our overnight temperature was around 32 degrees last night and we used 3 splits. We stayed very warm.

This is just a caution to the new wood burners. Most will tend to burn too much wood before January hits. It just does not take that much heat right now. Save your wood for when it is really needed.

Shouldn't take that much but we never know the "other" stuff ie, size of house, location, or if he just wants to sit in the house in front of the fire with wife! LOL! .

Backwoods Savage · Oct 23, 2010

NATE379 said:
It's pointless to have wood heat if you are only going to use it a few hours a day. I run mine 24/7 as do my folks. They have been heating for almost 30 years... so must be doing something right.

Ah Nate, but Palmer, Alaska has a bit of a different climate that most folks have on this forum. And I've been heating longer than your folks....but I do not always run the stove 24 hours per day. If it is needed, then it is no problem.

btw, we visited your area back in the 70's and really enjoyed it. Would like to return some time.

branchburner · Oct 23, 2010

NATE379 said:
It's pointless to have wood heat if you are only going to use it a few hours a day. I run mine 24/7 as do my folks. They have been heating for almost 30 years... so must be doing something right.

Yes, I think if you can't trust your stove to behave when you're in bed or away, after many years of use, then maybe you have the wrong stove. But you certainly want to get to know a new stove before you leave it alone. That means observing it closely during the daytime for many hours of use under different conditions (weather, wood types/sizes, air settings, load size, etc.). I would not be comfortable with my stove if it did not have a good degree of predictability. My comfort is based in a very long learning curve.

nate379 · Oct 23, 2010

They have been heating with wood since the early 1960s, just I was talking about at their current home and stove (Dad built the stove in 81 or 82)

Right now it's not cold enough to burn 24/7, been kind of warm with highs in the low 40s actually, but I meant during the winter. I sure as heck didn't buy a $2500 stove to just use the couple hours a day I am at home and not sleeping!

Backwoods Savage said:
NATE379 said:

It's pointless to have wood heat if you are only going to use it a few hours a day. I run mine 24/7 as do my folks. They have been heating for almost 30 years... so must be doing something right.

Click to expand...

Ah Nate, but Palmer, Alaska has a bit of a different climate that most folks have on this forum. And I've been heating longer than your folks....but I do not always run the stove 24 hours per day. If it is needed, then it is no problem.

btw, we visited your area back in the 70's and really enjoyed it. Would like to return some time.

jharkin · Oct 23, 2010

Gridlock-

Glad to hear you figured it out.

If it makes you feel better I had the same issues last year on my first year with the inherited Encore. I had to buy split wood so not wanting to kil it with marginal stuff I mixed in some of the very old wood in a small pile that was left by the PO. Some of that was bone dry punky stuff and I it just lit off so fast causing the temp spikes. Once I saw 2000 on the condar probe. Scary.

BTW, I discovered that it only takes about 15-20 minutes over 1800 for the cat hood and lower fireback to start glowing. Not good. This is also about when the roar starts.

Over time I found that on a full load; using fewer but bigger splits, letting it get good and hot before bypass and then leaving the air set at no more than straight down (~1/8) was a reliable overnight setup that would keep the stove in the safe zone.

~Jeremy

Backwoods Savage · Oct 24, 2010

NATE379 said:
They have been heating with wood since the early 1960s, just I was talking about at their current home and stove (Dad built the stove in 81 or 82)

Right now it's not cold enough to burn 24/7, been kind of warm with highs in the low 40s actually, but I meant during the winter. I sure as heck didn't buy a $2500 stove to just use the couple hours a day I am at home and not sleeping!

Backwoods Savage said:

NATE379 said:

It's pointless to have wood heat if you are only going to use it a few hours a day. I run mine 24/7 as do my folks. They have been heating for almost 30 years... so must be doing something right.

Click to expand...

Ah Nate, but Palmer, Alaska has a bit of a different climate that most folks have on this forum. And I've been heating longer than your folks....but I do not always run the stove 24 hours per day. If it is needed, then it is no problem.

btw, we visited your area back in the 70's and really enjoyed it. Would like to return some time.

Click to expand...

Nate, I couldn't agree more. If I am paying good money for a heat plant, I want that thing to do what it is supposed to do and in this case it is to keep my bottom warm.

I still shudder a bit with the OP on engaging the cat so soon. Sure, it works but knowing that the first burning of the wood is evaporating moisture and also knowing that moisture is a cats worst enemy, I wonder how long that cat will last. I'll stick to holding off a few minutes longer before engaging the cat and save a few dollars.

mettauercat · Oct 24, 2010

Pointless to me is having my house at 75 degrees while I'am in bed or at this place called work. I prefer to hold onto my investments for some time. Do not fool yourself, cutting, splitting, stacking, loading the stove, taking out the ashes adds up to a lot of time. Eighty gallons of propane for two years adds up to about $260.00 here in Va.. I burned about a cord and a half last year. $260.00 would not even begin to touch what it cost to rebuild one of these stoves. Sure I could burn it all night, and all day, If I wanted to. For what? To have a three story house at 72 degrees for an hour before we both go to work for 10 hours. No thanks.

Backwoods Savage · Oct 24, 2010

vc, on the other hand, having the house at 75 degrees all the time is not all that bad because all surfaces then are at the higher temperature. If they are allowed to cool, then it takes more fuel to get everything up to temperature. I know there have been times when we were away and had not built a large enough fire or the temperature was warm when we left home but a cold front blew through while we were gone. When we get home it seems to take a while to warm everything and everything we touch feels cold. Not so on a normal reload. Let's say you let the house cool to 70 but you feel more comfortable at 75. How long does it take for the air temperature to reach 75? How long before everything you touch does not feel cold?

These are just a common temperature thrown out for an example as everyone seems to have their own comfort range. For example, like many others I like 80 degrees during the summer months but get awfully uncomfortable at temperatures about that (this varies according to humidity levels). I also happen to like that same 80 degrees in the winter months but some folks seem to prefer their indoor temperature more in the 65-70 degree range.

UPDATE: Dealing with Excessive Catalytic Tempuratures

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