I had a thermocouple installed in my PH for the first season and a half of use because I was terrified of cat stalls. But it failed at the end of last season and I've been pleasantly surprised with the reliability of cat engagement even without that direct temperature knowledge. You can tell within a few minutes of a stall (always because I've shut it down too soon on a cool reload) by the lack of glowing near the little air inlet in front, and a flue gas temp below 400 (on my stove). If you don't have those two things, you don't have a burning cat.
Wow, that tells me a lot.. I had a feeling that my 350 flue temp reading after engaging the cat wasn't good,, I always open the draft to allow for a 400 min. flue gas temp... Are you talking about the little hole at the bottom front of the stove? You're saying that should be glowing or burning some coals? How did you position your probe to your cat? Since a probe reads right at the tip only I'm thinking of putting a slight radius in my probe and setting it on top of the heat exchange scoop and letting tip hang over the front of the cat or exhaust side... I have a K type probe coming with a ceramic cable that is suppose to be good for 2000 degrees.
Here's a pic: sharp eyes will count 3 thermocouples in there. The one going through the combustor didn't last terribly long despite being inconel jacketed type K's... good for 2000F. I should state for the record that this effort was due both to engineering curiosity, and the poor wash coat sourced problems with the early combustors. I have nearly 3 cords through my latest combustor and it works perfectly.
That's how I plan on running my probe , between the fins on the scoop and over the front of the cat... I just want to see how my cat works and compare flue gas temps like you did... How far open do you run your draft ? Do you ever run it just closed ? I have at times charred my reload wood just right and then shut the draft all the way and have had a blacked out stove for 4 hrs with no flame and temps on the flue probe and STT running @ 600.. I know the cat must be humming along then... Other times I try to duplicate this and I will see 450 ... I'm thinking getting my flue gases to 600 verses 450-500 creates the nicer cat burn when the draft is closed 100% Sometimes engaging the cat and leaving the draft open 1/2 for about 15 minutes and then closing 100% works to get a known cat burn going to ... Definitely a lot to learn about burning the PH.. I'm all ears about what others have found...
Ever consider dropping in a mechanical probe from the top... Is there room on the top of the stove where the cat lines up or are you into the main frame of the stove top? I haven't had the top off in a while to eye things up...
I don't think drilling through both layers of top would be practical even if someone would guarantee that neither layer would crack at the edge of the hole. I run fully closed all the time unless I'm aiming to charge up the house on a super cold evening before loading up for the night. Anything other than fully closed with my draft and I get 600 degree flue temps and my reload cycle cut in half. Your 350 deg flue temps may be fine for your stove and your house. Mine won't operate there, however, and a strong draft is the likely difference. The original stove innards used to result in much more time spent with a dark firebox then the stove experiences now. In fact I generally always have a little secondary action working away. I've considered draft control strategies, but haven't decided on anything yet. The stove is very reliable as is, and very easy for my wife to operate.
My probe will tell me what's going on in my draft situation,,,, after I compare to what I see with the flue gas temps and STT, I won't really need the probe,,,, maybe only to verify that cat has come to the end of it's lifecycle.. I guess you could say a cat probe would be handy to have while learning about your stove,,, comparing flue temps and SST to what the probe is reading... Once you have all three figured out,, the cat probe,,, you could probably do away with...
I think you will find yourself watching the cat probe more than anything else. It's the only thing I ever watch now. I know when to engage and when to reload and how hot the stove is just by looking at the cat temps. All that soapstone mass really gives a big lag time on surface temps and flue temps have a pretty long lag as well if your using a Condar thermometer.
Putting own cable probe together through input from another PH from the other site... The Condor cable probe can't take the heat, cable fails... Condor called me and said it would fail in my situation... Going with Omega...
Todd, Are you talking about a probe thermometer? Mine reacts very quickly. It can go from 300 to 700 in a very few minutes.
I think I used the Omega TJC36 in an 0.062" sheath diameter if I recall (the metal sheath was long enough to snake through the stove [36"]- the transitions to wires happened outside behind the heat shield). I would get something with larger leads and more insulation next time because even though they're rated for it, enough cycles will eventually cause the little ones to fail. Also, a thermocouple has very low thermal mass so you the response you see is very quick and jumpy. Buying something where the probe is bolted to a little chunk of metal will help to smooth the response curve which makes the reading easier to follow. A good example of this is the common Condor flue thermometer which is embedded within a long piece of 1/8"-ish brass in order to create an averaging effect. This makes it so the reading you see lags the actual reading by a minute or so, but it's much more stable. I also used an Omega i series panel monitor that I scored during a lab clean out at work. Good luck.
I'm just looking for a yes or no that the cat is engaged,,so I will see what happens when I get my probe from Omega... A close friend does instrumentation for high pressure boilers for GE,, he also burns a wood gun boiler, so I will talk to him more about a more permanent robust probe set up as issues arise... Maybe something I can direct towards Woodstock for a reliable probe set up... Right now I have sent them people to contact for HT silicone impregnated gaskets... I've used them before on a Paxo 60 gasification boiler,,, they rock.... any gasket smoke leaks are gone! Nothing sticks to them and they stay pliable creating a long life positive seal. Yes they are more money, but,,, trouble free operation... Once you use them, you will never use another gasket... You just got a taste of a more high tech world,,, enough said...
