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Terminology and new Wood stove tech

May 7, 2013
Terminology and new Wood stove tech
  • EPA Stove Terminology
    The wood stove terminology and new technology seen here can be like almost a foreign language to some People not familiar with the new stoves. I was a newbie here too, but I had a need to read and learn.
    Old stoves, are called non EPA (Environmental Protection Agency) rated or not EPA stoves, those are stoves produced before 1988. These stoves are also referred to as smoke dragons, Pre-EPA stoves or "air tight stoves". They are the old time stoves that can put out a chimney full of smoke, which is actually your fuel just blowing up the chimney and smoking out the neighborhood. They can maybe manage 35%-60% efficiency and waste 70% to 40% of your heat and wood.

    Non EPA rated stoves only have a primary air control that could shut off the air to a stove compleatly and may have a chimney Damper plate in the smoke stack. They use 1850 technology and are 157 years behind the times. Some models made efforts to encourage secondary combustion, but most did not accomplish this very well. They may have blowers and or heat mostly by radiant head with only nominal convection heat. They may or may not have a glass flame viewing area, usually not. The glass in these stoves is small and is always covered with creosote.




    Modern EPA rated wood stoves

    Run at about 70% efficient.
    Save you fuel costs by giving more heat with less wood.
    Little or no smoke up the chimney, if operated properly. Important for you and your neighbors health.
    Some have variable speed blower motors and heat exchangers
    Preheated dual primary and secondary air tubes that are combined into one easy to use operating lever. Or Catalytic converter controlled by a single rod.
    Some use automatic air floe controls
    Self cleaning large viewing clear ceramic panels, to see the flames, have air wash systems that blow hot air across the glass to minimize soot buildup, so that they only occasionally require cleaning.

    One big potential advantage is how clean the burn is and how much less creosote (and therefore danger) is produced by EPA stoves. For instance, a cleaner car might get double the MPG as another, but reduce emissions by 75%.....same with stoves. So while a new stove may only be 30% more efficient than the last generation, it reduces the smoke a lot more than 30%. Burned properly, a modern stove could reduce the smoke by 90% (40 grams per hour for dirty older stove vs. 4 grams per hour for newer stove).......not talking about EPA ratings here, but in-home use.

    Bottom line - everything is better with a newer stove...meaning, in general, one built from 1988 on.

    EPA RATED secondary burn stoves
    Modern EPA rated non catalytic stoves: run at about 70% efficient. They use preheated primary air as well as preheated secondary air. The preheated secondary air supplies a secondary smoke combustion chamber, through holes, whose purpose is to supply more hot fresh air to burn up the smoke from the primary combustion chamber and extract additional heat from the unburned gas to further warm the stove. The secondary smoke combustion chamber is located near usually above the primary combustion chamber and heated by it.

    Some models have separate secondary combustion chambers where pre-heated air is mixed with the smoke to finish burning it. A ceramic baffle can be used for the secondary burn chamber wall on some models. It is fragile, can be pushed out of place and or damaged. Most models have secondary combustion tubes in the main firebox that add additional air into the space above the wood for a secondary burn to burn un-burnt combustion gasses released by the first or primary burn . The secondary burn tubes can burnout and need replacing. These models are noted for their spectacular flame displays.

    Terms
    Primary air; start up air flow and used to control air flow to the stove, user controlled.
    Primary combustion chamber; firebox, where the wood goes.
    Primary air control provides measured preheated air to the primary combustion chamber.
    Secondary air; provides measured preheated air to the secondary combustion, air flow set at the factory, not user controlled, may be thermostatically controlled.
    Secondary combustion chamber; a area in the stove above primary combustion chamber or here it and heated by it to burn up the smoke from the primary chamber and further heat the stove.
    Heat exchanger; located above both the primary and secondary combustion chambers and receiving heat from both of them, cold air from your room is fan forced through the inside of these pipes, well warmed and released back into your room. (Used primarily in fire place inserts)
    Variable speed room air circulator fan; blows cold room air thru heat exchanger and back into room as hot air on some stoves and most fireplace inserts.

    Catalytic converter EPA rated wood stove
    Have all of the features and qualities on the non cat (catalytic converter) stove above except that:
    There is no secondary combustion chamber or secondary air tubes but instead, a catalytic converter like in your car whose purpose is to burn up the smoke before the smoke can go up the chimney. The catalytic converter also produces heat to help warm the heat exchanger and is about as efficient or maybe more efficient, depending on make and model, than the non-cat stove, but not by much , either way. The major difference is the catalytic converter is relatively easily damaged and may not last long if abused and costs $150.0 or more to replace.

    The catalyst somewhat fragile, and can be damaged by misuse; particularly by burning things other than properly seasoned firewood (the ONLY thing that should ever be burned in a stove). It is a consumable item that requires periodic replacement to maintain the clean burning ability of the stove.

    The catalytic converter can last up to 6 years on some models, with careful operation on your part. If you divide replacement cost $150 by 6 yrs = $25.00 to $40.00 /yr, allowing for price increases, to run a catalytic converter. Not an unreasonable cost.

    This repair bill can be avoided by buying the non-cat EPA rated stove or by very careful operation delayed.;Terminology_and_new_Wood_stove_technology_for_a_newbie.