Seeking advice and observations on catalyst woodstoves

[northcountry]

I've had a catalyst stove for a year now (bought a used Silent Flame from a neighbor) I replaced the combustor because the stove was 18 years old. The stove has a built in blower fan which I set to be controlled by the onboard thermostat. Once a certain firebox temp is reached, it runs the fan at either a low or high speed, depending on the temp of the firebox. Or it can be run manually at high speed anytime. I used the auto setting.

The stove seemed a bit fickle when it came to engaging the combustor because the flame would die down, which I understand is supposed to happen - a slower burn with a higher output due to the glowing combustor. But it could not hold the combustion temperature for long periods, even with a full load of wood burning well. I try to keep the combustor clear - vacuuming out the fly ash, etc. but eventually, I came to the conclusion that the stove does not like to have heat drawn from it by the blower fan. It burns far better for far longer without the fan running.

I am interested in any observations from others who have stoves with combustors and blowers.


One thing I am considering is to install a rheostat so I can run the fan at a low speed and get some heat movement without the cooling effect that the higher fan speed currently seems to produce. Plus it will be quieter.

 

[Corie]

What type of chimney are you running the stove on?

I believe this might be a big clue.

 

[northcountry]

Its a Duratech prefab chimney - I don't think there's an issue there because the stovepipe is straight up through the roof w/ no bends.
Chimney was brand new last year and there's always a good draft.

In thinking about it, it seems that the size of the firebox and my tendency to put bigger pieces of wood in after the fire is going might have something to do with it.
My second stove is a non-catalyst and it handles bigger pieces fine once the fire is hot.
This stove seems to prefer pieces that are split smaller.
Also, since the capacity is less, it may not be conducive to holding heat as well as a larger stove might be.
This is my first year using a stove w/combustor, so I'm still getting the hang of it.
I just wanted some input from others with a similar setup.

Also, I looked at the Q&A section of this site after I posted and I see that some of this is discussed there.
This site seems pretty comprehensive and I'm glad I found it.

 

[Todd]

Do you have a stove top or probe thermometer? What temp or how long til you engage the cat? Most cat stoves require a 500 degree temp before engaging the cat. And you should also wait 10-20 minutes after reloading to drive out moisture to prevent thermo shock. Cat stoves do take a little getting use to. Here are some tips on combustors.

www.woodstove.com/pages/combustortips.html

 

[northcountry]

Thanks for the link Todd. I don't have a thermometer.
I was using a rule of thumb that when the fan switched on, the stove was hot enough for the combusstor.
In retrospect, that was probably too soon.
My other mistake seems to be engaging it too soon after reloading - especially if I load bigger pieces.
Once this season is over (if it ever is here in MD!) I will remove and inspect the combustor.
BTW, my combustors came from stovecombustors.com - they're not a honeycomb-style, but one that looks more like a coarse sponge.
It was about half the cost of the standard variety.
Has anyone here had experience with them?
Supposedly, they light off as low as 380 deg F, but I'm not so sure...

 

[Todd]

A few people here use those combustors and I haven't heard anything bad about them yet. I think they are less prone to thermo shock than the ceramic honeycomb type and they do light off at a lower temp, but not sure how much that matters in the overall efficiency. Maybe with the competition of these new combustors we will see even better combustors in the future.

 

[Gooserider]

I don't have one of those combustors, but my understanding is that while they will MAINTAIN a light-off at lower temperatures than the OEM honeycomb jobs, they won't initially light off until you get them to about the same temp as the OEM units.

In other words, they will keep burning longer once they are going, but still need about the same high level of heat to begin with. Given how catalytic chemistry works, this makes sense - there is a certain minimum temp required to start the reaction, but once you've gotten lit off, the reaction itself supplies the heat needed to keep it going.

I think your comments and some of the earlier posters are pointing in the correct direction, that you need to wait longer, and get things hotter before engaging the combustor.

I would strongly reccomend getting a thermometer and learning how best to use it on your stove.

Gooserider

 

[elkimmeg]

This Manufacturer went out of business in the mid 80's the manual quotes code compliance to 1977 NFPA 211
The Cat used in this stove is an add on. It is nothing like the modern secondary combustion chambers of modern cat stoves
Its own manual clames 38% effeciency when max inlet air is open Nobody knows the condition or gasket seals to advise how to run that old of a stove addon Cat technology.

Here is a link to the manual I hope that helps some I have the stove combustors combustor in my stove the past 2 years but of modern technology it works very good

http://servicesales.com/woodburning/owners_manuals/Silent_Flame/SFowners.pdf

 

[webbie]

Elk is correct that this stove bears little resemblance to a modern Catalytic stove - so it may not be of much use for folks to report their experiences with more modern stoves. As a general rule, it might be fair to say that most stoves built after 1990 might be slightly more up to date....and, even then, a lot of earlier stoves had problems with cats being too close to the flame path, etc. and therefore early degradation.

I suspect your problem is due to some combination of poor design, lack of secondary air for the combustor and possible bypass leakage.

 

[northcountry]

Thanks for the great info folks. The pdf link is to what appears to be an earlier version of the manual that came with my stove - the date code on my manual is 9/88 and is specifically for the Model 2058. There is no efficiency data listed in my manual.
Here's a bit more background on my pre 1990 stove:
The date of MFG is stamped 10-88.
On that plate is printed the following:
"Certified to comply wth July 1988 particulate emission standards.
Not approved for sale after June 30, 1992."

I am going to remove, inspect, clean and reseat the combustors with new gasketing - apparently I should have done better because while vacumming it out, I noticed they moved rather easily in the housing and I had to slide them back into position.
Further inspection shows that not only should you apply gasketing between the combustor and the housing, but you should addtionally wrap each combustor with gasket, effectively doubling up on the material where it meets the housing.

So doing that should tighten things up a bit.
It's good to know that I have a decent set of combustors. This stove did its job well theis past winter despite these little snafus and I'm looking forward (in a perverted sense) to getting it in order and firing it up again in the fall.
One item no one has addressed - putting a rheostat on the fan motors - many newer stoves have these. Aside from containing more heat within the stove, this should quiet things down a bit - those fans get annoying after a while. Has anyone done a conversion of that sort? I figure it's straightforward as long as i get the right amperage of rheostat and don't cross wires...

 

[elkimmeg]

A lot of companies went out of business about the time when they had to comply to the EPA standards, that and cheapheating fuel cost. At one point 550 companies were selling stoves the number today in USa is about 18. you are right about the gasket tak pe neede for the combustor also do not forget to vax out any fly asy near the combustor placement.. If you leave it there it will find and clogg that combustor

 

[webbie]

As far as the rheostat, I suggest buying one that plugs into the electric outlet and then plug the stove into that.

Harbor Freight sells something like this - I think they call it a "router speed control" - it is also sold by some stove acc. companies.....
Here you go - $18 - can't beat it!
http://www.northlineexpress.com/detail~PRODUCT_ID~5SA-4008.asp

 

[northcountry]

Thank you Mr Webmaster!
This is great info and a good lead on the rheostat.
I was thinking along the lines of installing one in the stove, but why bother if I don't have to?

Thanks Again!.