cat stove owners. a question about air flow?

[ozarkjeep]

when you get the stove HOT, and engage the damper to put the cat in the exhuast stream, HOW MUCH intake air do you leave going?

50%, 25%? enough to keep some small flames?

I have no idea, ive tried engaging the cat, and reducing airflow alot, and it smolders, and looses temp.

IM trying to leave more airflow going now to keep some flames with the cat engaged.

any thoughts?

Im still unsure if I just cant get the process correct, or if Im trying with a defective combustor unit.

 

[ozarkjeep]

ok, here are some pics, its been burning for 45 minutes, with the cat engaged, and the airflow between 50% and 100% - I have adjusted it to make sure it isnt declining in top surface temp.

it varies from 390-540 on top surface temp right now.

and its steady, but ive got the air flow alot more open than it seems it should be.

possibly though, the exhuast going thru the cat instead of straight out the flu slows down the combustion?

is this not a big enough fire or what?

im needing some help here!

 

[elkimmeg]

Cat stoves are not flaming beast when the cat is engaged .Each load will vary a bit to loading spaces between logs moisture content. You will need to learn the primary air adjustment

390-540 on top surface temp right now

from the looks this is not a bad range to be, the fire looks normal

Today I took out my Cat in the Intrepid after a full year usage only fly ash.This is the Stovecombustor's replacement, paint brush, shop vac, and it was good to go, working perfect now
running 450 stove top. The Familly room is 74 degrees.

is yours good and clean? how old is it? condition?

 

[Corie]

what's your chimney system like? Generally it seems to me that setups with weak draft usually force you to keep the air controls open further than optimal, in order to keep the cat lit.

 

[ozarkjeep]

Elk,

this is the combustor that came in this 12 or so year old insert I bought.

https://www.hearth.com/talk/threads/4290/

It is possible that it has never been replaced.

the 390-540 temp variance is different areas on the stove top.
I can shoot the temp way back into the insert, and its hotter in the back ( near the flu)

the fact that you say that arent flaming beasts when the cat is engaged, almost completely solidifies my thoughts that this combustor is worn out.

if I engage the cat, and turn the intake air down low, the stove gradually looses temp.

EDIT:

Today, I removed ash from teh stove, and removed the combustor, I blew it out with weak compressed air, and went thru ALL of those holes with pipe cleaners.
after blowing it, there was NOTHING in it, some discoloration, but no dust, no obstructions, no build up.

It really looks more and more like the actual noble metal catalyst has been erroded from the ceramic surface.

Im just going to order another one and see what happens.

Cat stoves are not flaming beast when the cat is engaged .Each load will vary a bit to loading spaces between logs moisture content. You will need to learn the primary air adjustment

390-540 on top surface temp right now

from the looks this is not a bad range to be, the fire looks normal

Today I took out my Cat in the Intrepid after a full year usage only fly ash.This is the Stovecombustor's replacement, paint brush, shop vac, and it was good to go, working perfect now
running 450 stove top. The Familly room is 74 degrees.

is yours good and clean? how old is it? condition?

 

[ozarkjeep]

Hey Corie!

split level house, full masonry fireplace and chimey, the oval clay block liner was original, I installed a 316ssti ( whatever the hell that stainless ti alloy is) liner.

it took the full 20' flex liner, I trimmed maybe 4 inches from it to get the final fit.

I am not quite sure how to measure draft, but, I shoved a single sheet of wadded up newspaper into the top of the stove tonight ( trying what I read here, to heat the flu), and when I lit it, I scared the hell out of me!

it sounded like a rocket engine, and then the burnt newspaper was sucked up the flu, I could hear being sucked all the way up.

is that good or bad?

it seems to draft well in my limited experience, not really any smoke backpuffing with the door open.

thanks for your thoughts and ideas!

what's your chimney system like? Generally it seems to me that setups with weak draft usually force you to keep the air controls open further than optimal, in order to keep the cat lit.

 

[elkimmeg]

Sounds like it time to replace it it may only be working a fraction of its capabilities. you will use less wood and gain more control and produce a better heat range.

 

[ozarkjeep]

yes, thats about what conclusion I have formed as well.

Oh well, whats another $235 combustor to a $350 stove!

haha

 

[elkimmeg]

well if it works like mine, that will pay for its self in short time with heat produced and less wood used

 

[EatenByLimestone]

When I replaced my cat I found that I ran into a problem with the cat cooking a little too hot. I almost had to close the front damper down in order to keep the temperature under control. Then in the morning I'd have to open up the damper to burn off the coals. It's better now, but the damper is no where near as open as it was with the old combustor.

Matt

 

[ozarkjeep]

hey Matt,

so, are you saying a new combustor was hotter than your habits you had learned with the stove?

or a newer technology combuster was burning a bit too hot for the stove design?

thats one thing im not sure of.

so, when the cat is engaged..

you close the air intakes ( this prolongs the fire, basically a smudge fire, that burns the smoke) then the cat gets REALLY hot, and thats what generates more heat than a smudge fire would alone. ( burning the smoke)

if I engage the cat with a stove top temp of 500 degrees ( thats about 900 in side the underneath of the top- where the cat is)
will it get hotter?

or just STAY that hot with less air intake and fuel consumed?

i REALLY need to see one of these cat stoves in action, it would explain alot to me.

When I replaced my cat I found that I ran into a problem with the cat cooking a little too hot. I almost had to close the front damper down in order to keep the temperature under control. Then in the morning I'd have to open up the damper to burn off the coals. It's better now, but the damper is no where near as open as it was with the old combustor.

Matt

 

[EatenByLimestone]

I don't believe the technology was burning too hot for the stove. I have never seen the stove glowing and have not seen any of the white coloring normally associated with a stove that has overfired.

I am learning this too, I hope I can explain what I have observed.

When I swapped in the new cat, I also pulled down my stovepipe and ran a brush through it. I pulled much more out of my pipe than I care to admit, and I'm sure the cat I was using was partially plugged too. That being said, the stove has much more draft now.

When I start a fire, I need to close the air intakes more than I needed to when I had the old cat installed. The old cat did not burn as hot as the new one does. Most likely because it didn't reburn as much smoke as the new one does. When I first started burning wood in my stove, I followed, almost exactly what the owners manuel said the stove should be started and ran. After I replaced the cat I found the cat heating up the top of the stove to the point where the baffle would expand and stick on the stovetop supports. There really is only one way to control my stove and that is the air intakes. I now set them for 1/4 to 1/2 what the owners manual says.

I don't think I close the intakes enough to create a smudge fire. I only close them to the point where I can control the temp of the cat. When it gets down to a point I want it set at I open the intakes a little. I found if I opened the intakes too little I would have a good amount of coals in the stove in the morning. A little more air and the coals would take off. I guess when the cat superheats the pipe and really warms the chimney it pulls more draft. As it starts to burn down the draft isn't there and you get left with coals.

I engage my cat when my probe reads 500 degrees. I believe this is somewhere between 4 and 500. The cat from StoveCombustors.com is supposed to be able to light off at 380. It will quickly climb to what the probe says is 1600 if I don't start dampering it down.

I just took a pic of my stovetop after the cat has been engaged about 5 minutes. I'll take another on in another 5 and post them.

Matt

 

[ozarkjeep]

thank you very much eaten by limestone!

 

[EatenByLimestone]

I'm having upload issues with the camara, but I can let you know what the probe is reading and the regular surface thermometer beside it. My probe is reading 1100 and the stovetop is 400.

Matt

 

[DavidV]

Man, I gotta get a cat probe.

 

[Mo Heat]

... After I replaced the cat I found the cat heating up the top of the stove to the point where the baffle would expand and stick on the stovetop supports.

I've noticed a similar phenomenon with my stove (VCWW cast Iron Beheamoth), but it normally happens when I'm starting a new fire with the cat bypassed. I've concluded it is a 'local heating' thing and once the stove is in it's normal operation mode for 10 - 20 minutes and reaches an ambient operating temp by distributing some of that initially localized heat, everything is fine again.

What I actually notice is that when closing the damper, it feels a bit different in that the damper seems to be a bit more expanded on one side or something of that nature. Not a big thing, but I can feel the difference when I close the damper. After operating for a while, everything is back to normal and the next damper operation feels the same as always.

It will quickly climb to what the probe says is 1600 if I don't start dampering it down.

1600 - 1700*F are accceptable, continuous operating temperatures BTW, at least for most cat stoves. Even over 1700*F for short periods (maybe 10 to 15 minutes) probably isn't anything to worry about either. I've had one incident where I went well over the 2000*F mark on my digital cat probe thermometer with no problems. I reduced the primary air and it only lasted about 5 - 10 minutes. I was getting a little excited, but it came back down smoothly and settled in around 1600*F, then slowly dropped off over the next couple hours like it always does.

The real problems for a cat happen with sudden temperature changes that can thermally shock your element and cause damage or complete destruction (rare). This happens when your cat is (say for the sake of example) over 1000*F and you throw in a whole bunch of room temp wood (or wet wood that is boiling off 212*F water vapor--really bad) and immediately reengage the cat. The relative firebox temp has just been radically lowered and that relatively cooler air/smoke is bathing your super heated and very delicate ceramic cat. Yikes! Kind of like throwing water on hot glass. Not a good idea.

The typical slow, steady climb after preheating a reload, or a load introduced when cat temps are below 750*F, is nothing to worry about, even if it climbs rather high.

 

[ozarkjeep]

Good info Mo-heat,

thank you!

May I ask where and how much for the digital cat temp probe?

I want one!

But my stove has to have one at an angle or one thats read from the face of the edge, limited clearance.

 

[Mo Heat]

...May I ask where and how much for the digital cat temp probe?
...
But my stove has to have one at an angle or one thats read from the face of the edge, limited clearance.

I have this one: (broken link removed to http://www.condar.com/9-85.shtml)

It cost me over $100 and I spent another $15 or so at Radio Shack for an AC to DC 9-volt converter with 9-volt terminator. All in all, a bit pricey, but I haven't regretted it for a second. The piece of mind and precise control this thing gives me is hard to overstate. Looks like Condar now charges:

$89
$24
===
$113 (I think this is what I paid, as well)

May be some shipping, too.

Their non-cable, analog display, cat probe model is only $20, but you have to have access to the read-out. Won't work with an insert and will likely be mounted in an odd place for most cat stoves since the cat is usually hanging off the back.

Condar now seems to offer an AC adapter, but I didn't see a price. If you go the Radio Shack route for the AC adapter, I'd recommend getting a fixed voltage unit so you don't accidentally change the voltage and fry the instrument (display). The 9-volt pig tail was separate, but they allowed me to swap out the terminator for free (I had my pick of several terminators with the unit, but none of them was a 9-volt type). Before I bought that thing I was going through an expensive 9-volt battery every few days. I use the thing almost contantly. I have a tape measure on the couch next to me to extend my reach.

I like it. I have an insert so the probe is nestled beneath the convection shroud at the rear where there is no way to read a standard type thermometer. The cable on this one allows the probe to be in the back and the instrument (display) to be somewhere else. Of course, I had to install the probe with the insert out of the fireplace with the convection cowl removed. Lucky for me I bought it before the insert and had the installer put it in there before pushing it into place.

 

[ozarkjeep]

UPDATE:

I got the cat to lite by accident last night.

I was just past the kindling stage, and had several small ( 1" approx) splits in a criss cross fashion, laid a couple of larger splits over them.

left the air open all the way, and closed the cat damper after about 15 minutes, walked in to the next room to check emails, started talking to wife.

smelled something HOT, afraid something was burning, went back in, stove TOP temp was 500-650 ( various places)
closed off the air.

looked inside, and the combustor was glowing bright orange.

I adjusted air to about 50%, ( it was still falming pretty well)

after about 20 minutes the glow went away, and I wasnt able to light it off again, I ran out of smaller wood though, and the fire wasnt nearly as intense with a couple of big rounds.

SO...

new questions, how in the HELL am I suposed to keep the fire that HOT to keep the cat engaged?

OR is this a sign of a worn cat?

a newer unit will hopefully remain lit at much lower temps? ( by newer, I mean just a fresh catalyst, not different technology -stovecombustors cat-)

thanks!

 

[elkimmeg]

Can not answer that question I suspect the newer cat will light off easier and last longer than intermitten use of the old cat

 

[ozarkjeep]

also, from talking with Shane on this BBS, I cleaned the air tube that feeds fresh oxygen to the cat, and that might have helped it lite as well.

Ill experiement some more tonight when I have time, and see if I can get some consistant cat ignition, and burn times.

 

[Todd]

It sounds like your cat is on it's last leg. Have you looked outside at your chimney? When my cat is lit off and glowing all I see is white steam out my chimney, no smoke. The cat doesn't have to be glowing to work tho. Mine doesn't glow throughout the whole burning cycle. If you can't keep the stove up to temp on a full load and you have smoke out your chimney it is time for a new cat.

 

[Mo Heat]

I've never been able to get my cat to light off in less than 30 minutes. And that was doing some fancy wood stacking that reflected all the heat backwards toward the cat. I mean, I had a real conflagration going in there. That's not really a great idea because of the thermal strain of the quick heating of all the cast iron in my stove. Better to let things heat up slowly and steadily. Cast iron is some great stuff, but I like to treat it with respect to avoid heating one side of a thick panel too much quicker than the other side. This is one of the things that can crack cast iron (it's also what cracks or breaks glass BTW, like when you run tap water over a hot glass cooking dish).

I think you are trying to light that cat off way too quickly. Even with my cat thermometer I wait at least one hour before attempting to close the bypass and fire off the cat. While it is possible to get those things to light off quickly, without a cat thermometer, you will never be able to tell for sure. Better to err on the safe side and wait an hour before attempting it. That way you have a nice bed of coals and the newer splits you've added are rolling nicely in flames, contributing, rather than consuming, heat.

Once a cat is lit, provided it is not exhausted of its catalytic metals, it will remain lit. This is not something to worry about (with a good cat), but I'm not convinced that yours is lighting off properly. Certainly not after just 15 minutes of kindling.

Do this. Kindle your fire, then add some smallish sized splits. Let the whole thing go to coals, or nearly so during the first 30 minutes. Add a few more modest sized splits as the first load is nearing coals and let that burn for a second 30 minute period. Your stove will be at a pretty good operating temperature and ready to engage the cat. Then tell us what happens.

 

[ozarkjeep]

Mo,

out of alot of attempts to light it, last night was the first time, probably the longest ive left the air intake wide open with a smaller stack of splits in there too.

usually I wait ALOT longer to close the damper ( like an hour)

some of my wood is wet, and not seasoned very long.

so after several tries to lite the cat, I assumed it was bad, after cleaning and retrying, I felt certain it was bad.

so ive been closing the damper simply to slow down the born and direct more heat to the FRONT of the insert to radiate into the room instead of up the floor.

I wasnt even trying to light the cat last night, just trying save some of the heat from going up the flu.

I also watched secondary blue flame action all under and around the refractory plate for almost the entire duration of the cat being lit.

Ill try again tonight and see what I can get.

I was unable to go outside and look for smoke ,but I will be prepared to do so tonight if I can get it re-lit.

 

[Todd]

I've never been able to get my cat to light off in less than 30 minutes. And that was doing some fancy wood stacking that reflected all the heat backwards toward the cat. I mean, I had a real conflagration going in there. That's not really a great idea because of the thermal strain of the quick heating of all the cast iron in my stove. Better to let things heat up slowly and steadily. Cast iron is some great stuff, but I like to treat it with respect to avoid heating one side of a thick panel too much quicker than the other side. This is one of the things that can crack cast iron (it's also what cracks or breaks glass BTW, like when you run tap water over a hot glass cooking dish).

I think you are trying to light that cat off way too quickly. Even with my cat thermometer I wait at least one hour before attempting to close the bypass and fire off the cat. While it is possible to get those things to light off quickly, without a cat thermometer, you will never be able to tell for sure. Better to err on the safe side and wait an hour before attempting it. That way you have a nice bed of coals and the newer splits you've added are rolling nicely in flames, contributing, rather than consuming, heat.

Once a cat is lit, provided it is not exhausted of its catalytic metals, it will remain lit. This is not something to worry about (with a good cat), but I'm not convinced that yours is lighting off properly. Certainly not after just 15 minutes of kindling.

Do this. Kindle your fire, then add some smallish sized splits. Let the whole thing go to coals, or nearly so during the first 30 minutes. Add a few more modest sized splits as the first load is nearing coals and let that burn for a second 30 minute period. Your stove will be at a pretty good operating temperature and ready to engage the cat. Then tell us what happens.

Jeez, 1 hour seems a little paranoid to me. Your sending alot of smoke and heat up your chimney. From a cold start I light mine off in 15-20 minutes. I use lots of kindling and small splits at first, get her up to 600 degrees (probe temp), engage the cat, let it burn down to large red coals, then open bypass, refuel with larger splits, burn with alot of air for 5-10 minutes, engage the cat, then bring the air down til there are lazy flames bouncing around the top of the fire box. Stove top runs between 550-650.