Intrepid cat observations

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jetmech

jetmech

Member
Dec 8, 2007
228
Dillsburg PA
Heres the deal, just replaced the cat on my 1303 intrepid with a condar unit and installed a digital probe, yea i know im eat up with it as my wife says. First fire today with outside temps around 44 deg f. after getting stove top to 450 deg engaged damper and probe went up to 1350 degrees in a couple of minutes, keep in mind this is reading gas temp about 1/4 inch from cat outlet. stove pipe temp was 500 degrees when i engaged cat. i slowed the primary air after about 5 min and stove settled at 550 and digital reading is steady at 950 deg. cat is definatly working looking at chimney outside nothing but heat coming from cap. this is fun stuff for an old jet engine mechanic.
 
The cat thermometers will really improve the life of your catalyst. I have a VC Encore 2550 with thermometers at the inlet & outlet. I was surprised at how hot the Cat would get with the way I traditionally ran the stove - relying on the stove surface temperature & stack temp. It is very easy to approach 2000F, without a problem. And those kinds of temps will drastically reduce the life of your catalyst & the refractory that surrounds it.

I try to run with the cat inlet around 800 with the outlet running 1100-1200. As the the logs burns and the wood turns to coals, the cat inlet & out temps converge. I like the delta temp across the the cat - I know when its preforming - and I'll know in the future when it is depleted (no guessing).

And as you were saying, I have literally no smoke, just a heat distortion plume coming out of my chimney. As it should be on a good catalyst stove!
 
Thanks wood engineer, do your stack temps drop alot when your cat is engaged. mine went down to 250/275 with stove top temps at 600.
 
Ive also got a 2550 with steelcat and the probe thermometer. Also able to hit 1800-1900 occasionally if I'm not careful. The times I have caught it at 1800+ are usually accompanied by metal starting to glow and the sight of flames under the draft hood. not good.

I try and keep it under 1700.
 
My stack runs between 300-400, never much higher - even with a good fire going (running thru the cat).

Another thing I learned with the Cat thermometers is the 2550 does not do well with extremely dry wood. I have some 2 year old hard maple. If I load the stove up with a full load of that wood, I can not keep the cat temp below 1500, which I feel is too high. So I've switched so semi-seasoned red oak in the VC, and run the maple in the Tarm. The cat temp tracks very well with position of the air valve control lever. I put the air inlet lever at about 6 o'clock - and the cat outlet locks in at about 1100. Move it to 7 o'clock - it rises to 1250 or so.

To all you catalyst users out there, I highly recommend you set your stove up with at least an outlet thermometer. And inlet & outlet thermometer is even better. I have struggled with this stove for 5 years, and I finally feel I have it figured out. This season has been awesome.
 
wood-engineer said:
To all you catalyst users out there, I highly recommend you set your stove up with at least an outlet thermometer. And inlet & outlet thermometer is even better. I have struggled with this stove for 5 years, and I finally feel I have it figured out. This season has been awesome.
Click to expand...

Where do I get one of these? Also, there is only one hole at the back for the probe thermo. Is this where it goes?
 
Hey Diabel, i picked up my probe at a local stove shop. its made by condar.... My stove had a predrilled opening that was plugged by a chrome button. it is on the downstream side of the cat so im measuring temps after the cat. its very responsive to primary air, the more air the more outlet temp
 
wood-engineer said:
My stack runs between 300-400, never much higher - even with a good fire going (running thru the cat).

Another thing I learned with the Cat thermometers is the 2550 does not do well with extremely dry wood. I have some 2 year old hard maple. If I load the stove up with a full load of that wood, I can not keep the cat temp below 1500, which I feel is too high. So I've switched so semi-seasoned red oak in the VC, and run the maple in the Tarm. The cat temp tracks very well with position of the air valve control lever. I put the air inlet lever at about 6 o'clock - and the cat outlet locks in at about 1100. Move it to 7 o'clock - it rises to 1250 or so.

To all you catalyst users out there, I highly recommend you set your stove up with at least an outlet thermometer. And inlet & outlet thermometer is even better. I have struggled with this stove for 5 years, and I finally feel I have it figured out. This season has been awesome.
Click to expand...

This is exactly why my Encore 2550 had a warped Throat Hood and Upper Fireback after 18 months. I burned 2 year old hard maple and ran the stove hard: usually 650 stovetop temp. I SAW the throat hood glowing red on a regular basis.....yet the MANUAL simply says to keep stovetop temp below 750 to prevent overfiring...which I did......so I thought it was OK. It wasn't OK.
 
jetmech said:
Hey Diabel, i picked up my probe at a local stove shop. its made by condar.... My stove had a predrilled opening that was plugged by a chrome button. it is on the downstream side of the cat so im measuring temps after the cat. its very responsive to primary air, the more air the more outlet temp
Click to expand...

Hi Jet,

So it is a regular cat probe thermo. nothing fancy....and that predrilled hole - would that be your inlet (I suppose). What is the outlet then as mentioned before??? Also, I would think that it is not easy to read...
 
Its a digital condar, theres a probe about 4 inches long about 6 feet of wire and a digital read out unit.. powered by a 9 volt battery. mine onlr reads cat outlet temps. the opening in my stove sits just below the cat, airflow is from top to bottom on my stove.
 
Thanks Jet! I just checked mine & it would also be considered outlet since it would poke through the refactory box about 1/2 inch below the cat. I will check the Condar site & see if they have any. Also, how do you control the cat temp?
 
These cat thermometers sound like a great idea, I'm going to pick up a couple for my Encore and Intrepid II. Anyone using the regular (non-digital) condar models? I'm guessing I would need the 4" probe length for both stoves.
 
The only control on my stove is primary air, I close damper at 450 to 500 degrees and the readout starts climbing up to around 1300 to 1500 degrees. once i reduce primary air to a stove top around 450 to 550 the cat outlet will cool to about 900 to 750 range. when i look outside only heat coming from chimney. the cat outlet is very sensitive to primary air, the more air i give it the more outlet temp. and its almost immediate. even last night when stove cooled to 300 deg with coals slowing down cat outlet never got below 600. also i just replaced my cat and it made a difference in my intrepids performance
 
That is interesting. I would think that on a fresh load of wood, as you reduce primary air you begin to kill the fire (smolder) & the cat temp would increase.
 
While we're on the topics of catalysts, does anyone know the function of the secondary air controller? On the 2550, it is a spiral wound bi-metalic, with a probe that sticks thru the refractory - about 4" down from the cat outlet. Here is what puzzles me...

1. The air shutter, which is connected to the bi-metalic via a control rod (a bent wire), sits on a pin that keeps it slightly open at room temperature.

2. As the stove heats up, the bi-metalic moves in a direction to close the air shutter - which is already closed (sitting on the limit pin).

So I question what it actually does. It never deviate from the 5% open position - no matter how hot or cold the stove gets.

Anybody got a clue?
 
The probe is the same on my intrepid, as the stove gets hot it should expand the coil and start to close the shutter to decrease secondary air. My stove was at 650 the other day and i looked at my shutter and it was still wide open. i replaced the probe and coil during rebuild and i know the wire is hooked between the two, not sure why it wasnt closing... maybe takes more heat to start it moving. Also if you ever have a runaway stove you can plug the opening to cut even more air to your stove
 
As my 2550 is taken all apart I played with that secondary air inlet. When the stove is cold the flap is completely open, I put a propane torch to it in order to see if it works & within 3min of heat application the flap closed totally. Now, when the refactory was in place I could hardly see the probe sticking through. I am not sure how long the stem should be when new, but I am assuming that as it ages the tip burns off & the flap movement is affected.
 
wood-engineer said:
While we're on the topics of catalysts, does anyone know the function of the secondary air controller? On the 2550, it is a spiral wound bi-metalic, with a probe that sticks thru the refractory - about 4" down from the cat outlet. Here is what puzzles me...

1. The air shutter, which is connected to the bi-metalic via a control rod (a bent wire), sits on a pin that keeps it slightly open at room temperature.

2. As the stove heats up, the bi-metalic moves in a direction to close the air shutter - which is already closed (sitting on the limit pin).

So I question what it actually does. It never deviate from the 5% open position - no matter how hot or cold the stove gets.

Anybody got a clue?
Click to expand...


It feeds additional pre-heated air to the catalyst. Its sensing the temperature in the refractory chamber so its supposed to open up and let more air in if the cat cools off to far,but it also has that stop so it never completely closes and starves the cat for air.

It is adjustable, when cold you can usea screwdriver to turn the coil. The end of the coil that attached to the rod should be at the 4-5 o'clock position/
 
Great dialog on this stove. It's nice to have an engineer and a jet mechanic playing with this little fellow. These details have been perplexing several owners. Thanks for posting.
 
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