Please help me evaluate performance of new cat in VC Defiant Encore #2190

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jlggomez

New Member
Jan 1, 2021
24
Andes, NY USA
Thanks to all ahead of time. This is a follow up to a previous thread asking for help replacing catalytic combustor in my VC Encore Defiant #2190. Thanks again to Defiant3 for the help.

So, I replaced the cat and secondary air probe (OEM parts) in my #2190 which I have been running with a non-working cat. It was all actually easier than expected, fireback came out relatively easily and miracle of miracles the refractory box and cover were in good shape. I used the occasion to thoroughly vacuum out and clean everything as there was a good deal of old ash in there. What I am trying to determine is whether everything is now working as it should? I will describe what I observe Re temperatures and please tell me if it is all normal or not. Thank you again.

- I have two thermometers on the stove. The “Imperial” sits on the griddle and the “Condor Flue Gas” is the probe type that goes into the connector pipe. Btw, I have read references here to cat temperatures of 1k + degrees. How does one measure the cat temperature and how does that temperature relate to the temperatures that the griddle/flue thermometers display?

- Last night was the first night of use after the installation of the new cat and air probe and I was frankly a bit underwhelmed by the “improved” performance of the stove. I followed the instructions in the manual carefully. After the temperatures displayed were at 500+ degrees and with the air control lever fully open I closed the damper. As expected per everything I’ve read, the temperature dropped and settled at around 400 degrees on the flue probe thermometer. However, I was surprised to observe that it did not seem to go up after the drop as was also expected per my reading. I loaded the stove and closed the air control lever about half way and went to bed.

- This morning, the temperature on the flue probe thermometer read slightly above 200. The griddle thermometer read, as usual, about 100 degrees higher (300). There was a very good bed of very active coals in the box; more than usual after a typical night-long burn with NO cat and air control lever open only about 1/4. The glass on the doors, while not exactly clear, had less creosote (?) buildup than usual for a typical morning, but there was some black on them. Is this normal?

- I reloaded the stove. Temperatures rose quickly to 450 on the flue probe therm and about 550 on the griddle top therm. I closed the damper and with the air control lever fully open the temperature dropped to just below 400 on the flue probe and about 500 on the griddle therm. This time however, after a few minutes the temperature did rise back up to about 425 (flue) and about 550 (griddle) and has settled there nicely. All this with the air control lever fully open.

- Which of the two temperature readings should I be most concerned about?

- I assume that closing the air control lever partly or fully will drop the temperature accordingly. My goal is to get longer and cleaner burns with higher temperatures from the same amount of wood as before. I believe that is the point of a cat, no?

- Since the cat needs temps above 450-500 (per the manual) to activate, does that mean that if one lets the temp drop below that point during the course of a burn that the cat stops working and won’t activate again until the temp rises again to 450-500?

So, how does all this sound? Normal? If not normal, what should I be looking at to replace/repair. I guess I was confused and my expectations were possibly too high given what I have read about the very high temperatures that some run their stoves at. Btw, I don’t burn anything with higher than about 12-14 % humidity and when I say I “loaded” the stove, I mean about 60-75% of what I think I could actually get in the box.

Thank you all for your comments/suggestions and have a great weekend.
 
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Diabel

Minister of Fire
Jan 11, 2008
3,385
Ottawa, ON
Sounds pretty normal to me. One thing I would add it the cat probe. That would provide a full picture of what goes on during the burn.
 

begreen

Mooderator
Staff member
Nov 18, 2005
90,660
South Puget Sound, WA
Anyone else with a Defiant cat stove?
 

RandyBoBandy

Minister of Fire
Feb 25, 2015
1,270
Whitmore lake, MI
As diabel said these temps seem fairly normal. X2 on the cat probe. This is a must with this stove. Are you able to maintain flame in the box once the damper is closed? My stove pipe probe will drop to 400 every time I close the damper. If it falls below 400 then so does the cat temps. Higher cat temps will lead to higher flue temps. Most of us VC guys are using the Auber Instruments AT 100 digital thermometer. They only offer a 6” K-type probe so if you are using the rear heat shield you will need to drill a hole in it. Another option is to go to condar’s website and just buy their probe which is only 4” and will fit behind the heat shield. With no eyes on the cat you just have no idea if the cat is running to hot or to cool. 1600 cat temp seems to be the no go zone. Temps here and higher will destroy your cat. It’s been my experience if the cat is running steady at or near the danger zone then the flue temps are between 500-600 degrees. Hope this helps. If you have anymore questions just put them in the VC owners thread.
 

Rusty18

Burning Hunk
Nov 3, 2018
103
Belpre oh
+1 on the cat probe. I have the AT 100 that Randy mentioned, it is literally the only instrumentation on my stove that I trust. I have an encore 2550 so not the same stove.

I recently had secondary control issues and was seeing 1500-1600 at the cat with only 400-450 on the griddle and 300 on the flue (DISCLAIMER, I have 2 bimetal indicators on my flue, both are on at boiling point but one says 250 when the other is showing 400. IR says they are both wrong.)
 

jlggomez

New Member
Jan 1, 2021
24
Andes, NY USA
Thank you all again for your thoughts and suggestions. You guys are great! It is really appreciated as we‘re trying to get a handle on all this after running a stove which came with our house and with some issues. It was in pretty sad shape and I’ve been trying to get it up to speed a bit at a time. New gaskets, new glass and, as I explained above, replacing a non working cat and secondary air probe. As suggested, I will get and install (with your help) a cat probe. A couple of additional questions for now and comments please on something that happened yesterday that is of concern.

We had the chimney and flue swept by a professional about a month ago and I THINK that in spite of that we had a small (?) fire in the flue/chimney just yesterday. All seemed well with how the stove was performing as described above. I did my usual morning ash clean up and reloading and went out to do some snow blowing (brutal up here in Andes, NY). I happened to look toward the house and noticed an unusual amount of gray/white smoke coming out the chimney. My wife, who was inside the house called me and said that the griddle temp was reading 450, but the flue temp had risen to 900(!). We never let that temp rise above 500 or so. She closed the air control completely, the temp started to fall and settled to normal. My concern is, per Randy’s comments, that I damaged the cat. Is it possible for the flue temp to rise so high while the griddle temp remains that much lower? After temps settled down, we did recommend test of the cat (per the manual) by opening and closing the damper and observing the amount of smoke leaving the chimney. Here’s the weird thing:

The first three times that we opened and closed the damper there was much MORE smoke with the damper closed than with it open; the opposite of what should happen. Afterwards things returned to normal; much less or no smoke with damper closed and more smoke with it open. Is it possible the cat was burning up ash that had fallen in during the possible flue fire. Or, was the smoke from the cat itself? This morning all seems normal. We did the smoke test again and things appeared to be normal; more smoke with damper open.
; less or none with damper closed. Temps are as described in my original post. Obvious concern: could I have damaged the cat either with too high a temp or with ash?

Lastly (for now ☺). Still a source of some confusion is that the Condar flue probe therm reads that 400-900 is the “Normal” range. Yet, my Imperial griddle top therm reads that 500 and higher is in the “Overfire” range. If I get flue temps up to 600 I am well into the “Overfire” range and, as Randy states, in danger of damaging the cat. Or, are the two temperatures more ”independent“ of each other than I thought? If the griddle temp is at 450, which is the temp the manual recommends to fire the cat, what would cause the cat’s temp to rise so much; assuming that was what happened? What am I missing?

BTW, Re Randy’s question: Yes, I can maintain a little bit, not much, flame in the box with damper closed.

Thank you all again for the help and patience. Huge help!
 
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