CAT problems

[imacheezhead]

I replaced the cat with a steelcat in my CDW about 3 months ago. It was doing great until we had a stretch of extremely damp weather. The wood is kept under a roof surrounded by a tarp so rain and snow can't get to it. This doesn't help with 100% humidity for 2-3 days. I'm thinking that the wood may have absorbed some of that moisture and my steelcat hasn't been the same since. I'm having trouble achieving and maitaining light off temps. Sometimes on rare occasions I will get 1200 when I used to get up to 1275consistantly. I bring the wood in and place it behind the stove to help dry it before using it, but I'm not sure if that works. I have got a wood dampness gauge and it generally says the wood's moisture content is under 20% which from what I've read is pretty good. I'm starting to suspect that the cat is fouled. What are your thoughts and what is the best way to clean a steelcat?

 

[Woody Stover]

I don't know about ceramic cats, but I remember a thread where the steel cat were discussed and makers were quoted as saying that they were 'hyper-sensitive' at first, and would light off at super-low temps. As the new cats settled in, they performed more like ceramic cats. There are lots of variable governing how hot the cat will run, such as fuel used, draft on a particular day and probably others. I'd say that if your cat is lighting off when the probe is at or above 500 (specified for my 2460,) and you're not getting smoke out of the stack, only steam sometimes, then it's doing its job...
Hard to believe your cat would be fouled after only a few months. You're bringing the probe up to temp with the bypass open, correct?

 

[Woody Stover]

Here's the Condar cleaning manual:

(broken link removed to http://www.condar.com/combustorcleaningmanual.pdf)

 

[Jags]

You need to take a good look at that cat. It could simply be fouled and need a good cleaning. Make sure it is seated properly and that all the stove baffles (if any) are located where they are supposed to be.

 

[Woody Stover]

There is a cast iron baffle deflector plate between the firebox and the cat above that the smoke passes through. It breaks up the flame to prevent impingement . The holes in the plate are maybe 3/8" square, but I suppose they could be clogged. You can poke a small caliber brush through those holes to clean them, just don't shove it through too far and hit the cat. Or you can just use a small screwdriver...( Also, you should be able to see the cat glowing if you look up through the glass from down low...hard to see unless you get the right angle.)

 

[Ashful]

I have the same trouble as the OP on damp days, when it's been rainy and wet several days in a row. I don't think the wood is really absorbing that much moisture to it's core, but there is definitely going to be more net moisture in or on the wood. Also, your draft is usually weak on these days, as they tend to be warmer days, this combination making it very difficult to achieve cat light-off.

My solution: a few splits of dryer cedar, pine, or even 2x4's in the bottom of the stove, under my normal cord wood. Bring stove up to 500F stove-top temperature with draft full-open, then go to half draft for a while longer to hit 600F on the stove top. Try engaging the cat, and see if she takes off. If not, go back to bypass and run at a draft setting low enough where you won't be overfiring the stove, while toasting the wood a while longer. On real bad days, or with real bad wood, this can mean running 20 - 30 minutes in bypass with the air mostly closed, to get the wood well charred and dried, and the chimney well-heated, before the cat will finally take off.

It's not fun, and sometimes very frustrating, when you're rushing to get out the door. However, it always works, with enough time.

 

[Backwoods Savage]

Wood is not a sponge! That moisture that gets on the outside is only that; exterior moisture. It takes very little time to dry that. What counts is what is on the inside and if you have not given that wood enough time to dry right, it is bad for the cat. We still do not know how to burn water.

As for the wood being out in the weather, we have done that for much longer than others have burned wood. It was only a couple years ago that we began putting wood in the barn that we are to burn in the winter. Yet we never had a problem with wet wood before. If it rains or if it snows, it takes usually less than 24 hours to dry that moisture. Of course if one were to stack near a building with no eave trough and all that roof water were coming down on the stack, that could be a different thing but that would be rare as I doubt many would do such a thing.

Simple solution. Cut, split and stack your wood outdoors for 3 years and problems just magically disappear. Yes, get 3 years ahead on your wood and you'll never want to go back. Well worth the work to get there even if it takes a couple years to reach that point.

 

[Ashful]

Wood is not a sponge! That moisture that gets on the outside is only that; exterior moisture. It takes very little time to dry that. What counts is what is on the inside and if you have not given that wood enough time to dry right, it is bad for the cat. We still do not know how to burn water.

Wood is a sponge. This is why wood floors and table tops expand in humid summer weather, and shrink in a dry indoor winter climate. Wood always seeks the ambient humidity of the environment it is in, whether that be wetter or drier than its current state. In the case of not-yet fully-seasoned firewood, you are correct, the trend is downward. This is because the ambient environment (for most of us) results in MC < 20%, and he's dealing with wood at MC > 20%.

However, here, he's trying to burn wood that is physically damp from sitting outdoors in several days of rainy conditions. You are correct that the surface moisture dries very quickly, perhaps 1 - 3 days of dry weather will get it back to it's pre-rain state, but he's trying to burn it wet today!

I would argue that excess moisture on the surface of the wood, when you're trying to get a stove going, might be even more frustrating to the user than an equal amount of moisture stuck inside the wood. The real question is how much moisture can be held by the surface of the wood. Is it even remotely comparable in mass to an extra few % of moisture content in the wood?

 

[Backwoods Savage]

Wood is a sponge. This is why wood floors and table tops expand in humid summer weather, and shrink in a dry indoor winter climate. Wood always seeks the ambient humidity of the environment it is in, whether that be wetter or drier than its current state. In the case of not-yet fully-seasoned firewood, you are correct, the trend is downward. This is because the ambient environment (for most of us) results in MC < 20%, and he's dealing with wood at MC > 20%.

However, here, he's trying to burn wood that is physically damp from sitting outdoors in several days of rainy conditions. You are correct that the surface moisture dries very quickly, perhaps 1 - 3 days of dry weather will get it back to it's pre-rain state, but he's trying to burn it wet today!

I would argue that excess moisture on the surface of the wood, when you're trying to get a stove going, might be even more frustrating to the user than an equal amount of moisture stuck inside the wood. The real question is how much moisture can be held by the surface of the wood. Is it even remotely comparable in mass to an extra few % of moisture content in the wood?

Somehow you sound just like a neighbor of mine. He too argued the point about the wood floors, doors, etc. We stood next to one or our wood piles when discussing this and I had made a comment about how much the wood pile had shrunk. He, like you, argued about the wood floors, etc and said the wood pile would do the same thing. So, we took measurments. That wood pile has never grown even 1/16 of an inch in any kind of weather but it has shrunk. So sorry, the argument still stand that wood is not a sponge. We are talking here about firewood, not a wood floor in your house.

 

[Ashful]

Somehow you sound just like a neighbor of mine. He too argued the point about the wood floors, doors, etc. We stood next to one or our wood piles when discussing this and I had made a comment about how much the wood pile had shrunk. He, like you, argued about the wood floors, etc and said the wood pile would do the same thing. So, we took measurments. That wood pile has never grown even 1/16 of an inch in any kind of weather but it has shrunk. So sorry, the argument still stand that wood is not a sponge. We are talking here about firewood, not a wood floor in your house.

BEDEMIR: Exactly! So, logically...,
VILLAGER #1: If... she.. weighs the same as a duck, she's made of wood.
BEDEMIR: And therefore--?
VILLAGER #1: A witch!

Your logic does not fully support the argument, Dennis. Your firewood pile always shrinks, for the reason I had already stated above: the moisture content of the wood in your pile is above equilibrium for your relative humidity, and so it is still shrinking. It's always going to seek 10 - 18% MC, depending on your local climate. Actually, single digits, if you're in the desert southwest! If the MC of your wood is above that, your pile is always shrinking, as you clearly observed. If you're below that, your pile is always growing. Wood is a sponge.

According to a study [1] done by the USDA, the equilibrium moisture content of your beautifully dried stacks in Michigan will vary from 12.3 to 15.1 percent, throughout the year. Because your wood is a sponge. This follows the relative humidity for your climate, plotted here at 70F. Relative humidity goes up, and your equilibrium moisture content goes up, but you'll not see your stacks grow unless they're already at MC below 15%.



This is all trivial to the guy trying to burn wet wood. His issue is not whether or not the wood has absorbed significant moisture, or if it has grown, but the fact that his wood is damp. I stand by my original statement, as I've experienced this several times in the last two years: "I don't think the wood is really absorbing that much moisture to it's core, but there is definitely going to be more net moisture in or on the wood. Also, your draft is usually weak on these days, as they tend to be warmer days, this combination making it very difficult to achieve cat light-off."

[1] - (broken link removed)

 

[webby3650]

Maybe running it with the Ashpan door open smoked the cat? As I re-call, you closed the by-pass, and opened the ashpan door to get the cat temp up. That might be the problem with the steel cat.
https://www.hearth.com/talk/threads/dutchwest-by-pass-help.100945/

 

[imacheezhead]

Maybe running it with the Ashpan door open smoked the cat? As I re-call, you closed the by-pass, and opened the ashpan door to get the cat temp up. That might be the problem with the steel cat.
https://www.hearth.com/talk/threads/dutchwest-by-pass-help.100945/

Wow what a wealth of information this generated. I'm really impressed!!

Prior to the steelcat I used ceramiic CATS and one of the symptoms of overfiring a CAT is crumbling of the ceramic substrate and I have never had that happen. I will bring the CAT up to temp using the ashpan door only for a very short period of time and I closely monitor it. In the other thread I stated that I started to use the loading door air damper and I did for several days until I was rudely remonded why I stopped using it many years ago. What happens is I get chuffing like a steam engine and smoke starts barreling out of the damper, so back to the ash drawer door again. I know that the bypass should remain open (no CAT) until lightoff temperature is achieved, however since the gasses essentially go directly out the flue instead of through the CAT it takes FOREVER to accomplish this. I was curious if high temps were resposible for destroying the platinum catalyst, but I found that the melting point of platinum is 3,215! That's way higher than anything the stove can generate, but I still am very careful about not leaving the draft open to long.

I got suspicious about the damp wood after those very damp days because that's precisely when my problems started. Don't go so far as to say I am burning "wet wood" because I'm not, however the surface of the wood seemed to take on some additional moisture which led me to believe that the CAT may have become fouled. Like I said in my original post, I have a moisture meter and the MC was around 17-20%, which is not bad, but that was a day or so after my problems started so the wood may have had a chance to dry out a little. I was able to take the CAT out of the stove and the baffle holes are clean, (they're round by the way). There was some ash material on the surface of the CAT so I gently brushed it off and then used compressed air to blow out whatever was inside. This did seem to help a little, but it still ain't the same as it was before the dreaded "damp days"! The cleaning instructions provided by Woody Stover is actually something I already have and is more for a ceramic CAT. Esp. the part about using a pipe cleaner. There is no way you can use a pipe cleaner on a Steelcat. The vinegar solution part may work though.

Thanks again for all the help guys. I really appreciate it!

 

[imacheezhead]

BEDEMIR: Exactly! So, logically...,
VILLAGER #1: If... she.. weighs the same as a duck, she's made of wood.
BEDEMIR: And therefore--?
VILLAGER #1: A witch!

Your logic does not fully support the argument, Dennis. Your firewood pile always shrinks, for the reason I had already stated above: the moisture content of the wood in your pile is above equilibrium for your relative humidity, and so it is still shrinking. It's always going to seek 10 - 18% MC, depending on your local climate. Actually, single digits, if you're in the desert southwest! If the MC of your wood is above that, your pile is always shrinking, as you clearly observed. If you're below that, your pile is always growing. Wood is a sponge.

According to a study [1] done by the USDA, the equilibrium moisture content of your beautifully dried stacks in Michigan will vary from 12.3 to 15.1 percent, throughout the year. Because your wood is a sponge. This follows the relative humidity for your climate, plotted here at 70F. Relative humidity goes up, and your equilibrium moisture content goes up, but you'll not see your stacks grow unless they're already at MC below 15%.

View attachment 93479

This is all trivial to the guy trying to burn wet wood. His issue is not whether or not the wood has absorbed significant moisture, or if it has grown, but the fact that his wood is damp. I stand by my original statement, as I've experienced this several times in the last two years: "I don't think the wood is really absorbing that much moisture to it's core, but there is definitely going to be more net moisture in or on the wood. Also, your draft is usually weak on these days, as they tend to be warmer days, this combination making it very difficult to achieve cat light-off."

[1] - (broken link removed)

Special techniques are used around doors and windows in log cabins to compensate for the logs swelling and shrinking.

I stack my wood on a concrete floor about 6' high under a roof and by the next day the pile is a couple inches lower. I just attributed that to settling.

 

[Woody Stover]

I gently brushed it off and then used compressed air to blow out whatever was inside

Sounds like you're experienced with the cat so I assume you know to blow very gently when using compressed air, otherwise you can blow the catalyst off the substrate!

 

[Ashful]

Sounds like you're experienced with the cat so I assume you know to blow very gently when using compressed air, otherwise you can blow the catalyst off the substrate!

Yep. Also, the problem with catalysts failing due to overtemperature has nothing to do with the platinum or palladium melting. It is more a delamination problem, and that typically begins to occur around 1800F.

 

[Woody Stover]

I will bring the CAT up to temp using the ashpan door only for a very short period of time and I closely monitor it. In the other thread I stated that I started to use the loading door air damper and I did for several days until I was rudely remonded why I stopped using it many years ago. What happens is I get chuffing like a steam engine and smoke starts barreling out of the damper, so back to the ash drawer door again. I know that the bypass should remain open (no CAT) until lightoff temperature is achieved, however since the gasses essentially go directly out the flue instead of through the CAT it takes FOREVER to accomplish this.

What cat stove are we talking about here? And how long is "forever?" Takes me about half an hour on a reload if the stove temp has dropped pretty low, a little longer with a top-down start. I ramp 'er up pretty gently, though. By the time I close the bypass, I've cut the air pretty far and the load is barely flaming...

 

[alex johnson]

Somehow you sound just like a neighbor of mine. He too argued the point about the wood floors, doors, etc. We stood next to one or our wood piles when discussing this and I had made a comment about how much the wood pile had shrunk. He, like you, argued about the wood floors, etc and said the wood pile would do the same thing. So, we took measurments. That wood pile has never grown even 1/16 of an inch in any kind of weather but it has shrunk. So sorry, the argument still stand that wood is not a sponge. We are talking here about firewood, not a wood floor in your house.

I pleasently have to disagree with you. Wood is a sponge for the simple fact that, if you placed that stack of firewood underwater for a week, it wood start to soak up moisture, guaranteed! And that pile wood grow. But since we don't put wood underwater to season it. The only reason that its getting smaller because it is in a dry enviroment.

 

[Hardrockmaple]

I've burned with a Steelcat for three winters now in my DW 2460 with no noticeable deterioration. On a cold start (using a modified top down light off) I can have the stove up to 1400 with the damper and air shut down in less than an hour without opening any doors. I typically shut the damper at 350 with primary air wide open, within 10-20 mins. I cut the primary back to half, and shortly thereafter close 'er down and walk away.

I've no idea what happened to yours and I've never heard of burning one out but damn your making that thing hot in a hurry using the ash clean out.

 

[Backwoods Savage]

Your logic does not fully support the argument, Dennis. Your firewood pile always shrinks, for the reason I had already stated above: the moisture content of the wood in your pile is above equilibrium for your relative humidity, and so it is still shrinking. It's always going to seek 10 - 18% MC, depending on your local climate. Actually, single digits, if you're in the desert southwest! If the MC of your wood is above that, your pile is always shrinking, as you clearly observed. If you're below that, your pile is always growing. Wood is a sponge.

According to a study [1] done by the USDA, the equilibrium moisture content of your beautifully dried stacks in Michigan will vary from 12.3 to 15.1 percent, throughout the year. Because your wood is a sponge. This follows the relative humidity for your climate, plotted here at 70F. Relative humidity goes up, and your equilibrium moisture content goes up, but you'll not see your stacks grow unless they're already at MC below 15%.

This is all trivial to the guy trying to burn wet wood. His issue is not whether or not the wood has absorbed significant moisture, or if it has grown, but the fact that his wood is damp. I stand by my original statement, as I've experienced this several times in the last two years: "I don't think the wood is really absorbing that much moisture to it's core, but there is definitely going to be more net moisture in or on the wood. Also, your draft is usually weak on these days, as they tend to be warmer days, this combination making it very difficult to achieve cat light-off."

My most humble apology to the OP as I had not intent of getting this thread off topic so this will be my last post to answer Joful.

So my firewood pile is always shrinking. How long until it is gone? And if it soaks up moisture like your floor, it should then expand rather than shrink. And how much could I expect it to expand. But then you state it is always shrinking. It just makes me curious as to how long it will take a 4' high pile to get down even to only one foot tall?

According to your USDA study, you say my stacks should vary from 12.3 to 15.1 percent. That is interesting because of the statement that the wood will sort of match the relative humidity. I can assure you that I have never witnessed a 12-15% relative humidity in this area. However, maybe I've never left the wood long enough to dry? But certainly not to that low of a humidity.

Another interesting point is that we did some experimenting with some of our wood. We found some at 8% and several below 10%. Yet, our humidity in this area just does not get this low. The stack I referred to earlier has not shrunk nor has it expanded in the last 2 years.

You stated, "...you'll not see your stacks grow unless they're already at MC below 15%..." I have to ask, how would our wood get that low in humidity with your theories. In addition, if indeed our wood was below 10% moisture and it had been stored outdoors for 7 or 8 years, why was this wood not smaller than it was? How did it get that low in moisture? And, of course, how can the wood pile continue to shrink if, as you say, it can increase in moisture, or as you state, soak up moisture like a sponge?

But my biggest problem still is to determine that if my wood pile always continues to shrink, how long before it is gone? Or one also has to wonder about some of these old barns. How on earth have they stood as long as they have? Why are those beams not toothpick size after a couple hundred years? Or why has not the 2 x 4's in these old homes disappeared?

I stand my my statement and that wood is not a sponge. Of course if it is punky, then it will soak up like a sponge but it is beyond the point of being much good for anything by then. Perhaps we need to take many pieces of different types of wood and weigh them on a weekly basis for x amount of years to see just how much they shrink? I'll leave that to you.

 

[Ashful]

My most humble apology to the OP as I had not intent of getting this thread off topic so this will be my last post to answer Joful.

Actually, it's entirely on-topic. The OP was concerned that their wood getting wet during rain or snow events is affecting their catalyst operation. I agreed it is a possibility, to which you countered, "wood is not a sponge." I'm simply explaining the error in your statement.

So my firewood pile is always shrinking. How long until it is gone? But my biggest problem still is to determine that if my wood pile always continues to shrink, how long before it is gone?

So now you want to argue about this? I thought the topic was "wood is not a sponge." The statement that you have always observed your piles shrinking, and never growing, was made in response to your prior post:

That wood pile has never grown even 1/16 of an inch in any kind of weather but it has shrunk.

Perhaps I misread what you were trying to say there. However...

According to your USDA study, you say my stacks should vary from 12.3 to 15.1 percent. That is interesting because of the statement that the wood will sort of match the relative humidity. I can assure you that I have never witnessed a 12-15% relative humidity in this area.

Again, a distraction from the debate at hand, "wood is a sponge." However, what I said was entirely correct, and you are failing to grasp a basic concept, here: moisture content is not relative humidity. As already stated three times in my post which you quoted, the moisture content of the wood in your stacks will decrease (or increase) until it is at equilibrium (i.e. "steady state") in a given relative humidity. This does not imply the moisture content is the same value in percent as the relative humidity. The "moisture content" of your wood is a ratio of the weight of the water in your wood to the accepted oven dry weight of that wood. "Relative humidity" is a measure of vapor density, relative to that required to completely saturate the air at a given temperature. They do not track 1:1, as clearly shown in the graph I previously posted.

If you disagree with the USDA paper, that is fine. If you presume you're more knowledgeable on this subject than the authors of the paper, then I assure you they would be very eager to receive your corrections on their work!

 

[Jags]

Riddle me this...How can interior moisture of wood be at less than average MC outside? This is very common, by the way, many areas average over 20%Rh yet their firewood will be less than that.

 

[Woody Stover]

Relative humidity is an expression of the amount of water the air is actually holding at a given time to the amount of water the air is capable of holding before it starts precipitating out as dew, not an expression of the ratio of water weight in the air to the weight of the air and water, as the MC of wood is.
[I have no idea if this is actually right, but I thought it sounded good. ]
Actually, Battenkiller explained this once, and I think this is basically how it went.

 

[Jags]

Relative humidity is an expression of the percentage of water that air is capable of holding before it starts precipitating out as dew, to what it is actually holding at a given time, not an expression of the ratio of water weight in the air to the weight of the air, as the MC of wood is.
[I have no idea if this is actually right, but I thought it sounded good. ]
Actually, drfera (?) AKA Battenkiller, explained this once, and I think this is basically how it went.

Actually - that was my back handed way of showing how we are comparing two different measurements.

Sorry - I do a lot of "instructing" for my job and try to find ways to make peeps think.

 

[Woody Stover]

Sorry - I do a lot of "instructing" for my job and try to find ways to make peeps think.

Yeah, I think that's what Joful said anyway. Lately, all my thinking has been about how to get enough wood dry (super-dry) in time.

 

[Jags]

Yeah, I think that's what Joful said anyway. Lately, all my thinking has been about how to get enough wood dry (super-dry) in time.

Actually - I even caught myself on a mistake. Typed MC when it should have been Rh. ( I fixed it. )