Catalytic Wood Stove - Fire Flare Up

[NYSB]

I have a catalytic wood stove (Regency CI2600) which some people have had difficulties with but I have been very happy with mine. I am getting around 10-12 hours of actual heat on most full-load burns and up to 24 hours in which I have enough coals to re-load the stove. It heats our 2000sqft home very well. But I have noticed a phenomenon of flair-up and wonder if this is a characteristic of all stoves, catalytic stoves, or just the model I have.

In my typical burn cycle I will re-load at some point on a bed of red-hot coals. Once the new load of wood is burning well and the exhaust gets to 500deg on the internal thermometer I close the bypass damper. Once the temp begins to shoot upwards of 1000-1200 deg I begin turning down the main air intake - this does not take very long. For overnight burns I turn it down all the way until just a few "lazy" orange flames are evident on the wood, with secondaries present. Exhaust stream temp hovers anywhere from 900-1250 or so, depending on amount of wood and moisture content. On many burns, after maybe 30-60 min or so of maintaining this temperature, the wood just ignites and burns with much more vigorous flames. I cannot turn the primary down any more. The exhaust temp may go up a little, but not much - certainly staying within proper range for this stove. It's not a runaway fire by any means - just a much more vigorous burn. When this happens a get a little bit less total burn time, maybe 8-10hrs rather than 10-12. So is this just a characteristic of catalytic stoves, or just mine? There is no air leak around the door gasket as far as I know (I've checked).

SB

 

[quotejso]

Maybe turn it down earlier unless you need the heat.

 

[webby3650]

My Blaze King runs exhaust temps as high as 650 and as low as 200. Your exhaust temps seem really high for a cruising cat stove. I can only reach temps like you are seeing if the bypass is open.

 

[Woody Stover]

Your exhaust temps seem really high for a cruising cat stove.

He may be talking about the cat thermo?

 

[webby3650]

He may be talking about the cat thermo?

Could be. I didn't think that stove had one though.

 

[TheRambler]

You just need to turn down the air sooner in the process. You have a cat, so very geberally speaking you should do somethibg like this to get max burn times. Load stove and let it rip full tilt for 10-15 minutes to allow the wood to get burning and char up. Then start turning down the Air, how quickly depends on how vigorous the burn. Within another 30 minutes it should be shutdown fully. However, once that wood is chared well and the cat is active you could shut it down immediately.

Every stove is a little different, so the time may vary a bit. But essentially once the wood is burned enough so that it will continue smoking adequately and rhe firebox has reached 500F at the cat then you should be able to shutdown fully and get a cat only burn.

I dont have the sane stove. But if i am doing a reload into an already hot stove then i can usually close the bypass within 5 minutes, and have my air shutdown fully within another 10-15 minutes and the cat will take it from there for the next 12-14 hours

 

[BKVP]

The ability to operate your stove at its lowest possible burn rate and keep the cat active, as designed by the manufacturer, will require sufficient draft. Your manual should tell you the w.c." of draw necessary.

If you are experiencing delayed ignitions, excessively dry fuel or too rapid and reduction in combustion air can have that result. Or your flare ups could just be the logs collapsing in the fire.

Rereading your post, you could also have excessive draft. When the wind blows or stack effect is increased due to dropping outdoor temps, in a manually operated air control, a minimum amount of air is prescribed by design to pass the EPA test and burn cleanly. If the wind is strong enough or the stack effect great enough, more air will be pulled into the stove firebox and the stove will burn hotter.

Consult the manufacturer for recommendations.

 

[NYSB]

Thanks for the replies. Just to clarify, I am measuring the temperature internally, right at the exhaust of the cat, with a Condar temp probe that is designed for this purpose. This temperature is necessarily much higher than stack temps or surface temp of the stove. At these temperatures, nothing is glowing red that's not supposed to be... These 'flare-ups' do not happen with every burn - maybe about half the time. Often when I am re-loading on a bed of coals I can activate the cat (close the bypass) when the thermometer reads only 400 degrees and within a couple of minutes the cat has lit off and the temp rises accordingly. When starting from a cold stove I burn with the damper mid-to-full-open and the bypass open until the cat temp is 500, then I close the bypass. In either case I will typically turn down the primary air control as soon as possible - this normally takes less than 10 minutes. Unless it is the coldest part of the winter, I never need to run the stove more than 1/4-open on the primary air control. Most overnight burns I utilize the fully 'closed' position. I might try closing the boost air all the way to see if that helps. What I would like to see is nothing but glowing red wood, with just a trace of primary combustion flames, and a glowing red cat. That goal may not be achievable with a manually-operated air control stove, but it's good to have goals. I guess then I would have a Blaze King! But we just had to have the flush insert.... But I still do love the Regency - it may not go 24 hours, but it goes long enough.

I agree that what must be happening is that somewhere along the way it is getting more air that I would like. Too much draft is an interesting question. Despite the fact I am using a non-insulated liner in an external masonry fireplace, my draft appears to be quite good. I've never measured it, but I've never had issues with smoke backing up or other such problems.

Anyone suggest measuring the draft? Is there some way of decreasing the draft in the chimney if there is too much?

SB

 

[Nick Mystic]

I have observed the flare up phenomenon you described in my secondary burn stove - Jotul F600. When it occurs in my stove it usually only lasts a few minutes before reverting to the previous burn pattern. I chalk it up to an irregularity in the wood. Perhaps a small pocket of sap wood firing off, for example. Another possibility I've considered is an air channel developing in a burning log that has diverted some primary air to a particular spot making it burn hotter for a time.

 

[webby3650]

This insert is a hybrid correct? Cat and secondary combustion tubes?

 

[Smoked]

I don't know the right term but mine have always seemed to "gas out" at about an hour or so into a burn with larger loads. It seems like the splits reach a certain stage and release remaining energy all a once. If I do a large load with similar sized splits and they all go at once, it is a raging inferno for a while. This happened in my first house with the new Heritage and only a 15 ft stack. I now use a combo in split sizes to stagger that stage a little more. Very large split with smaller stuff around for longer burns. That stage is very pretty but if already near max STT, a little unnerving.