First time with a cat temp probe

[jharkin]

Joful is right that its not always about the cat probe temp to determine how it will light off. It does seem to also depend on the temperature and composition of the gases going up the flue. On a small hot load I can sometimes close before I see 500 on the probe and the hot gases will warm it up enough to launch. On the other hand on a really big load I have sometimes seen that even if its reading 500 or more it wont always light off until Ive let the load burn a bit longer. Might be too much smoke and not enough oxygen smothering it?

The max temps relate to how big the load is and how much control you have. When doing full loads if you use small splits or soft woods its easy to spike the temps badly since everything starts off-gassing at once. Bigger the load the bigger the split and denser the wood is my rule. Save the big oak logs for overnight and use chunks and uglies in the daytime!

BTW, 10 hours since I put those 4 splits in and the house is still at 71F. nothing but one small glowing coal left in the box tho. Probably be tough to get it relit.... I'll leave it for the night and restart tomorrow if its cold.

 

[Ashful]

Well, this is new. I let the wife drive the stove today, as I was out fetching another cord or three of big ash, and she called me in a panic at one point. Seems the stove top was up close to 650'F, as she didn't remember to shut the air down far enough early enough.

I explained the process of lowering the air a little at a time, keeping the cat below 1700'F, while working the stovetop temp down. I later received a report that the stovetop was down below 400, and the cat never exceeded 1200'F... while she was watching the meter, anyway.

So, tonight I light a fire, and can't get the cat to light off for anything. It's just following the stovetop temp, currently 380'F and falling, two hours into the burn. Earlier in the evening, I had the stovetop up to 600'F, and the cat barely got to 500'F.

The longer this goes on, the less my wood seems to be the culprit. It can't take two hours to steam out a load of medium splits, can it? Maybe it's just the temp probe, or the gasket on my bypass damper. Maybe my wife killed the cat?

If anything, I thought the 1700'F I hit the night before was hotter than she'd have had it, and it still worked great after that.

 

[jharkin]

Joful I dont think you killed it with temp. 2 years ago I wasn't paying attention one day and had an accidental overfire. The upper fireback inside the stove was glowing dull orange, flames where shooting OUT from the cat inlet into the firebox, and the temperature probe read 2000F.

Scary as %(*&$%

Cat still works just fine today. And somehow nothing warped.

 

[Ashful]

The cat just lit off ten minutes ago, nearly four hours into the burn. I think this one can be chalked up to wet wood, or perhaps operator error. Here's the full story for those smarter than me to figure out:

Had lit the fire around 8pm, and engaged the cat a half hour or forty minutes later, at 475 stovetop. Cat only got to 380'F, so I left the air open wide, thinking it would only be a matter of minutes until it lit off. Stove top went to 600'F, but cat never got above 500'F. Had good flame in the firebox the whole time, so the stove was venting, no signs of a plugged cat.

I had lowered the air after that, and we had been watching our typical dull, glowing firebox, with intermittent whisps of flame the last several hours. Stovetop was crusing somewhere around 350'F, and the cat was holding almost the same temperature. If I hadn't had a cat probe to tell me otherwise, I'd have thought everything was crusing beautifully.

Almost four hours into the burn, the firebox suddenly took off, climbing above 550'F again, with good flame show. Air control was still almost fully shut, so it seems the next log in the stack just went up with a bang. To our surprise, cat temp soon shot up to 1058'F. I bumped the air control down to the stop (it was almost there already), and now we're down to 500'F stovetop and 839'F cat.

I don't think I had engaged the cat too early, or made a mistake by leaving it engaged when it did not light off. Sometimes doing this will kill the fire, so then I go back into bypass, but this time the fire seemed unaffected by the un-lit cat. Too me, this is an indicator of too much moisuture in the wood, or exhaust somehow bypassing the cat, but I'd like a more experienced opinion.