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Mosca 12-18-2005 03:38 PM

Tricky Wood Stove Question
I have an air-tight wood stove with a catalytic converter and a metal "smoke" shelf.

This wood stove was a gift and is my only heat source. Yesterday the metal smoke shelf fell down as a result of poorly designed threaded connectors. A number of the custom sized threaded bolts have been lost in the ash (perhaps weeks, months, or years earlier)

I am presently working to resolve and restore the "smoke" shelf to its intended function by repairing and re-threading the connector bolts and locating new (custom?) nuts and washers.

The wood stove's integral catalytic converter is now, of course, exposed to the fire directly-- unshaded from the fire's radiant energy by the now-absent smoke shelf.

My question is: Am I taking any known risk by exposing the catalytic converter directly to the radiant heat of the firebox? Does anybody know of any damage that this direct radiant exposure could cause to the catalytic converter? Catalytic converters are certainly designed to sustain the usually high air temperatures present in stove flues-- but I am ignorant of what effect the direct unshaded radiant heat from a firebox would have.

It is very cold outside now (7300 feet elevation in the Rocky Mountains); and the wood stove is badly needed. Repair is ongoing; but may well take weeks or more as parts are either found or built here on site.

I will be building needed fires in the now simpler firebox because of the weather. What risks am I taking other than the normal wood stove maintenance issues?

If this question strains the knowledge base available here, I would be grateful for any links you could provide to other internet sources. (Google is not very informative for wood stove questions)

Thank you for any help you can provide.

Bonus 12-18-2005 10:58 PM

I'm no expert, but I've heated with wood my entire adult life, and can see no danger happening, except that I think you'll go through a lot more wood without the shelf in to slow everything down. It should also have the effect of cleaning the converter which can be a problem, over time it can build up with gunk and be hard to burn hot enough fires to get it clean with the shelf in the way. I wouldn't worry personally, but if you do, call the manufacturer and see what they say.

Mosca 12-19-2005 10:57 AM

Thank you, Bonus

It's good to know that a side benefit will be the cleaning of the converter. My location (New Mexico) provides an abundance of pitchy wood and frequent cleaning is a requirement.

20 years with wood stoves--but also no expert.

Thank you.

Denison 12-20-2005 02:11 PM

Re: Tricky Wood Stove Question
Catalytic combustors are ceramic with a semi-precious metal coating. Direct exposure to flames will degrade this coating rapidly and ruin the combustor. It is called flame impingement. The cleaning effect of the flames on the combustor that Bonus described is off track. Combustors clogg because 1: they are degraded normally after 2-5 years of use, resulting in no combusting of unburned gasses which then condense on the too cool combustor, clogging it. 2: There is a user opperated bypass damper that should be kept open upon fire starting so unburned gasses don't flow to the cumbustor until the temperature of the stove reaches a point that will then trigger the chemical reaction between the smoke (unburned gasses) and the cumbustor. Once this point in temperature is reached (check the thermometer), close the bypass and a good cumbustor will then start working to burn the gasses that are only now being forced to flow through the more restricted passages of the clean and pre-heated cumbustor. If the bypass is not opened upon start-up the unburned gasses will condense on even a too cool, brand new combustor, clogging it. Don't burn anything but dry wood... no galvanized nails or trash:eek: . Newspaper creates fly ash that will clogg the combustor too. Firestarters are the way to go.
The shelf (baffle plate) you descibed as missing is a design feature that the performance of the stove depends on... call a wood stove shop and ask for a chimney sweep they recommend to inspect the stove... it's worth it! If the shop wants to inspect for you, be prepared to have them suggest you buy a new stove. You may have a beyond repair stove ...but a sweep will be more objective in helping you make that decision, plus most sweeps are much better at troubleshooting that woodstove shop installers and can look at the chimney which plays a major role in system performance and safety. Good luck!

Mosca 12-20-2005 04:59 PM


Thank you for your help.

I realise that advise based upon an unavailable inspection is dicey, but I will still inquire based upon what my non-expert observations allow.

The wood stove is about three years old. So perhaps the converter needs replacement very soon anyway. I don't know if it is replaceable or removable--it seems integral.

In the past two(?) days I have allowed the exhaust from 400 degree fires to be directed thru the converter. Henceforth I will keep the bypass damper open and direct no exhaust the converter. The converter may therefore already be degraded.

It seems to me that you are, therefore, recommending replacement of the converter, if possible at this time-- possibly, God forbid, the entire stove.

I am attempting repair/rebuilding of the smoke shelf asap.

A sweep's inspection is not feasible given my current resources (I am unemployed and will have sufficient income no sooner than February).

I am unimpressed with the design of this (Big Box Store Name Brand) product, and will replace it as soon as feasible. My landlord purchased it.

However, it is likely that present realities will require the use of this stove for the duration of this winter.

I assume that if I operate this stove with the bypass open, prior to shelf repair, I will likely be okay. Once the shelf is repaired, the converter should be used--but it is likely that it will be less than fully effective until the converter is replaced (if this choice is available).

Am I overlooking anything?

Thanks again to both of you for you inputs.

jproffer 12-20-2005 05:16 PM


My landlord purchased it.
Well now...that throws a different light on things. I know nothing, and I mean ZERO about wood stoves and such, but I do know about rental property and I know that (at least in Illinois) the LL is responsible for any permanent fixture and it's maintanance and/or replacement. He is, afterall, going to retain ownership of it after you leave. Call him or her, be civil (or try to be...but remember they only deserve the level of civility that they give you in return), and request that this matter me taken care of right away. First time...request, second time...demand "nicely"...Third time...have a good lawyer demand "not so nicely"

BTW before making any of these calls, make sure the law is the same there as it is here.

Bonus 12-20-2005 06:15 PM

Always learnin', tks Denison.

Denison 12-22-2005 12:42 AM

Landlords and Stoves
This must be a fairly casual rental relationship. Most landlords are skitterish when it comes to woodstoves. Here in Oregon alot of wood is burned for heating homes. Landlords are either the first to call for a sweep or they remove the stove. They are liable if they have an uninspected installation and there is a fire. Since he bought the stove he has a very good reason to make sure it is safe.

Back to the combustor... they all can be removed from the stove since they all have only a handful of years to live before a replacement is needed. Most don't even need tools to remove but there are many different makes and not knowing what you have...

You can leave the bypass open but stay alert to the fire and control the air at the primary draft controls so the flue is not overheated . You will be wasting lots of heat (fuel) by keeping it open but until you get the baffle plate fixed... hopefully soon. 400-500 degrees is usually plenty high for good heating. By the time it gets that high you should have a well established fire and could surely think about restricting the air to about one fourth open.

I would consider asking the landlord at least when the last time the chimney was swept. Is this stove hooked up to a brick chimney, fireplace or a metal chimney and if metal is it a straight shot up from the stove.


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