Catalytic Combustor Operation Temps in Intrepid II?

[DoubleClutch]

Well, I just replaced the CC for the first time on our VC Intrepid II and I am impressed. Whenever we tried to get it to work in the past 10 yrs (stove came with the house), closing the flue to go into catalytic combustion just seemed to make the fire die down slowly. Also never noticed any difference in quantity or quality of smoke. Considering that I had cleaned the thing many times, and the cat was intact and looked good, I wondered whether the whole thing was a gimmick or just simply would never work in our setup for some reason.

After replacing the cat a few days ago, tonight I threw on a big dry hnk of white pine. Got her up to 550° or so and clamped down...and it got HOTTER instead of COOLER! It works, apparently!

EDIT [burning plastic questions removed]:

I'm curious about when to use the cat and when not to use the cat.

The old (circa 1987) manual says not to engage the cat until 450°F ... but then it says, "When thermometer readings drop below 350°F, it's time to adjust air control for a higher burn rate or to reload the stove."

Are they saying you can keep the cat engaged until it drops to 350°F? I'm confused about this 450°F versus 350°F issue...will I foul the cat with pine resin if the temp on a pine fire drops to 400°F before I disengage the cat?

Just trying to get used to the idea of a real, working catalyst. Thanks,

J

 

[EatenByLimestone]

Plastic is generally bad to burn cat or not.

Matt

 

[oconnor]

burn wood.

 

[bmwbj]

DoubleClutch, I to have a Intrepid II stove, and for the first 2 years I could never get the
cat. to "light off"... I purchased a new cat. from condor assuming the new stoves cat was bad. NOT
I than purchased a probe thermometer for the stove pipe and inserted it about 18" up from the stove
top. Now I can monitor the exiting smoke temps more carefully, and can get the cat to "light off" every
time.
When I have a good bed of coals, I rake coals to the rear of the stove as to cover the inlet of the "hood"
with red coals. This will heat the "bypass air" so the cat lights easier. I then put in about 3 or so 3" well
seasoned splits and close the doors. When the stack temp probe thermometer reaches 1000 deg. I engage
the bypass, and I have cat light off every time.
The probe thermometer stays at around 800 to 1000 untill all the wood is gone and its time to reload.
Usually 3 splits of well seasoned wood (mainly) maple and oak will last about 2 to 3 hours. I will slowly turn
the Primary air back to try and maintain 500-600 on the grittle temp.
I am not 100% sure this is the correct method, but I do know it works every time for me and I never
have smoke outside. The sweet smell of a cat burning properly is all I have.

 

[jpl1nh]

Once you engage the cat and get it to light off, it will feed on the particulates in your exhaust stream. The cat burns those particulates generating a lot of heat in the process, the more smoke (particulates) the hotter the cat will burn. Even if your fire box temp drops, as long as you have a smoke supply, the cat is self sustaining, generating its own heat from the combustion of the smoke until the point where your fire is down to coals and producing no more smoke. At that point it doesn't matter whether the cat is lighting off or not since there is no more polluting smoke exiting your chimney. Just having the remainng smoke free exhaust stream continue to pass through your cat at that point is in no way harmful to your cat. Therefore, you have no reason to disengage it until you load your next load of wood

 

[Backwoods Savage]

Well said jpl1nh.

 

[DoubleClutch]

Great replies, thank you. I think I understand a little better, now. As the wood burns and the temperature drops, there is less vaporized flammable sugars, esters, alcohols, etc., in the smoke until all you're burning is the carbon in the coals, in which case the cat does nothing.

BW, do you know of any good sources for a stack probe thermometer like the one you use? I'm thinking that might be a good idea for me. (I have my stove set up with rear exhaust.) Thanks again.

 

[moondoggy]

holy cow 1000 degrees?
when my griddle is over 500 and when the same stupid magnet thermo about 3" from the collar is over 550.(which probably means 700inside)
1000 scares me....unless its there and i dont know it.
i engage, hear a sight roar.....couple of tic tic's... within minutes the stack temps drop ... like a lot, and stove temps rise.
i get light off 90% of the tiem this way.

sorry to hijack.. but..
BMWBJ-- and anyone else, when you engage the cat, and it burns, the result, I thought, was actually lower stack temps.
you mention the probe stays 800-1000.
Further- you mention you cover the hood? i've been afraid to do that.. like crud will get in and clog the combuster no?

 

[oconnor]

holy cow 1000 degrees?
when my griddle is over 500 and when the same stupid magnet thermo about 3" from the collar is over 550.(which probably means 700inside)
1000 scares me....unless its there and i dont know it. ...

Keep in mind that the 1000F is flue gas temp on a probe, vice surface temp on the magnet mount. Liners in Canada are tested to sustain operation at 1200F for extended periods, and 2100 F during a chimney fire for short periods, without external flue temps rising beyond certain levels.

But in the end, it is still hot, but probably what we all would get on a probe thermometer at many points during the season..

 

[jpl1nh]

holy cow 1000 degrees?
when my griddle is over 500 and when the same stupid magnet thermo about 3" from the collar is over 550.(which probably means 700inside)
1000 scares me....unless its there and i dont know it.
i engage, hear a sight roar.....couple of tic tic's... within minutes the stack temps drop ... like a lot, and stove temps rise.
i get light off 90% of the tiem this way.

sorry to hijack.. but..
BMWBJ-- and anyone else, when you engage the cat, and it burns, the result, I thought, was actually lower stack temps.
you mention the probe stays 800-1000.
Further- you mention you cover the hood? i've been afraid to do that.. like crud will get in and clog the combuster no?

Yeah, I have the same experience, lighting off the cat, will temd to bring down and stabalize my stack temp. I would guess that's due to reduction in air flow when you divert through the cat. 1000 sounds hot to me too, yet the cat will often be up in that temp range or above when its really chewing on a lot of smoke, I suppose measured close enough to ithe cat you might have those temps.

 

[bmwbj]

Alright Guys, I know you all think I'm crazy, but those temps inside the flue pipe
is what I get every time the Cat. is lit and stays lit. Those stack temps do drop as the wood
slowly turns into a coal bed.
My probe thermometer is about 18" up from the top of the stove. I can reach this temp
in about 10 min. from the start of a cold stove and a good "handfull" of kindling. It must be
measuring the passing flames as the climb through the stack. I do have a really good draft, so
maybe the flame are reaching that high. My single wall black pipe is 3 sections long leading into the double
wall pipe at the ceiling thimble. It is a straight shot from the stove to the sky, about 20 feet in total.
When the cat is lit, I can maintain the stove temps easily between 400 and 600 steadily, and
the stack probe thermometer maintains a steady 1000. "No Glowing Parts" The cat must be burning the gasses and I am measuring that temp with the probe thermometer. I don't know if This is normal, but it works
every time and the total chimney length is always clean. About a cups worth dust every year.