Destroyed my cat. ...how'd it happen??

[emt1581]

I had enough of my home being chilly so I went to start a fire. Now over the summer I swept the chimney real good and cleaned out the pipe inside the house. But I forgot to clean the cat. Usually all I do is run a vacuum hose/brush over it to suck out any ash.

Well this year when I went to clean it, before lighting it up, I discovered the honey comb had a 2" hole burned through it.

How could that happen??

I never allow my stove to overheat very long. And I vacuum the comb once or twice a season, since I usually burn 24/7 throughout.

Any ideas here?

It was 3 years old. Do they just wear out??

Now I get to buy another one. Anyone know of a place to get them cheap? I think the cheapest I saw was on ebay for $200.

Thanks

-Emt1581

 

[McKeznak]

...Well this year when I went to clean it, before lighting it up, I discovered the honey comb had a 2" hole burned through it.

How could that happen??...

You sure it was burned through? and not chewed through?

 

[Jags]

First - YES cats are a consumable part. They do need replacement on occasion. Some can go for several years, others get only a few years out of them

I never allow my stove to overheat very long.

Too high of heat can be an early death to a cat. I am not sure if the quote above is a slip or accurate, but overheating a cat will lead to a shorter life span.

 

[begreen]

Did you always open the bypass before lighting a fire and on reloads?

 

[jharkin]

Is it ceramic or stainless?

Thermal shock (from loading wet wood and re-engaging too early with a cat that was hot from a previous cycle) can crack a ceramic cat.

 

[Nick Mystic]

I ordered a new catalytic cumbustor for my Woodstock Classic last year for around a hundred dollars from this place: http://www.woodstovecombustors.com/ It arrived fast and has worked fine. I would recommend them. They even included a gasket for free.

 

[emt1581]

I ordered a new catalytic cumbustor for my Woodstock Classic last year for around a hundred dollars from this place: http://www.woodstovecombustors.com/ It arrived fast and has worked fine. I would recommend them. They ever included a gasket for free.

(broken link removed to http://www.woodstovecombustors.com/vermontcastings2.html)

$202 plus shipping I'm guessing.

Honestly, money is pretty tight right now and I didn't notice a huge difference in burn times with the cat so I might just let it go for a while. Mine is a 2 in 1 so I CAN burn with or without.

Thanks though.

-Emt1581

 

[jharkin]

If its the 2in1 the cat might still be under warranty. Worth a phone call to find out....

 

[Ashful]

Cat's are consumable, in that the metals plated onto the ceramic substrate are slowly consumed, but the substrate itself should not fail under proper use.

Wood stove catalysts are typically warrantied for 5 years (pro-rated), so you should get some money back on your cat that failed after 3 seasons.

Stove temperature and cat temperature have absolutely nothing to do with one another, and in fact operate in complementary form during the early stage of the burn cycle. Closing down the air supply will reduce stove temps, but will almost always raise catalyst temperature, during this early part of the burn cycle. Do you have a temperature probe on your cat? If not, get one.

Here are the basic failure modes of a cat:

- Temperatures over 1800F will cause the catalyst plating to delaminate from the ceramic. Not an instant-death scenario, but definitely shortens its useful lifetime. This is most often caused by resinous woods (walnut is the one that gives me the most trouble), or loading too many small splits, which off-gas too quickly in the early part of the burn cycle. When you see your cat probe climbing to 1800F, open up your air control, which will allow more of the gasses to be burned in the firebox, reducing the load on your cat. If you're stuck between overheating your stove and overheating your cat, then it's time to open the bypass damper.
- Direct flame impingement can cause the same type of catalyst plating peeling that you see in a classic cat over-temperature scenario.
- Plugging with ash is caused by burning garbage, cardboard, improper firestarters, etc.
- Plugging with creosote is caused by engaging the cat too early, especially burning wet or pitchy woods, such that it's in the smoke path without being in the active (500F+) region, as measured on the cat temperature probe.
- Poisoning is caused by burning many different chemicals, including painted wood, pressure-treated wood, garbage, plastics, lots of galvanized nails, etc.
- Cracking and all mechanical failures are caused by rapid temperature change. Hot to cold (throwing a big load of cold wood in and re-engaging before the steam is sufficiently baked out), or cold to hot (engaging a cold cat during a vigorous burn, causing direct flame impingement on a cold cat.

If I saw a hole thru the middle of my cat, I'd assume thermal shock resulting in cracking and failure, nothing else. I don't think you can get a cat hot enough in a wood stove to actually burn thru ceramic.

 

[Highbeam]

Even if you choose to bypass the cat and burn in non-cat mode, start the process for getting a new cat since your warranty is based on time. If they won't give you anything then you can run in non-cat until you decide to trash that stove.

 

[Ashful]

If they won't give you anything then you can run in non-cat until you decide to trash that stove.

Depending on his stove, it may not be his decision. I've seen some users here report that their cat stoves were almost entirely uncontrollable without the cat installed, essentially going straight into self-destruct mode, when they tried to burn without a combuster installed. I've not experienced this myself, but I don't own the same stove as the OP, either.

 

[jharkin]

Depending on his stove, it may not be his decision. I've seen some users here report that their cat stoves were almost entirely uncontrollable without the cat installed, essentially going straight into self-destruct mode, when they tried to burn without a combuster installed. I've not experienced this myself, but I don't own the same stove as the OP, either.

He owns the 2in1 which is actually designed to run with or without. The combustion chamber for the cat is set up to work in the old VC noncat "everburn mode with the catalyst removed.

But unless they made big improvements over the everburn system, I know I'd want to keep that cat in.

 

[Heatsource]

great post Joful

 

[Sprinter]

great post Joful

+1 Should be a sticky.

 

[Trktrd]

If it's designed to have a functional Cat, I would replace it before long term use. I tried to burn without one installed and the stove took off like a runaway nuclear reactor.

 

[begreen]

At Jag's recommendation I made a wiki article from joful's nice post. It would be helpful to add why a metal cat might fail and the differences between metal and ceramic cats.

https://www.hearth.com/talk/wiki/why-catalytic-combustors-fail/?noRedirect=1

 

[Ashful]

Cool! I think some of the same applies to steelcats, excepting the facturing of the ceramic caused by rapid temperature change. I guess steelcats are new to most of us, so we're still figuring out new ways to kill them.

 

[jharkin]

Oh I found out how to kill mine.

2000 degree overfire.

Doesnt crack but the cat warps from the heat (sag in the middle) and turns grey as all the active material stripped.

 

[Todd]

BKVP has been preaching door gasket leaks as a big cause of thermal shock. How's your door gasket holding up?

I also remember many threads on VC stoves where they seem to burn very hot in that rear chamber and even have a dull red glow. Maybe a cat thermometer would be a good idea.

 

[jharkin]

BKVP has been preaching door gasket leaks as a big cause of thermal shock. How's your door gasket holding up?

I also remember many threads on VC stoves where they seem to burn very hot in that rear chamber and even have a dull red glow. Maybe a cat thermometer would be a good idea.

Not sure if you are talking to me or the OP or both.... But yes, probe thermo is a must on any downdraft CAT stove I think. I have one and its how I noted the 2000F (rookie mistake a couple years ago - very cold night, very big dry load, left he stove unattended before I had it closed down all the way)

As far as the door gaskets and thermal shock, I wonder if its more of an issue in BKs since the cat inlet is right up front by the door?

 

[Ashful]

I would expect a door gasket leak to cause an overtemp issue, not shock. What's the theory behind a leaky door gasket causing thermal shock?

Just so we're on the same page, thermal shock = rapid change in temperature.

 

[jharkin]

I think we cross posted Joful. On the BKK, the flue gasses enter the cat right up at the front of the firebox above the main door. I think a leaking door on a BK can allow the cold air to get sucked straight into the catalyst without being warmed passing through the main box as they are in our stoves where the cat inlet is in the back.

 

[Todd]

You guys are probably right, a leaky door gasket on a down draft type stove probably won't effect thermal shock like it would on a BK or WS, but I could see it contributing to overfires or a 1800+ cat.

 

[jharkin]

Number one source of bad things happening on a Vermont stove is the ash pan gasket.

 

[Augie]

I think everyone is totally off base here, I think it was curiosity.