Wood burning heaters aka “wood stoves” come in two main configurations; standard non-catalytic wood stoves and catalytic wood stoves. Modern wood stoves are typically combination appliances that deliver heat via both radiation and convection:
- Radiant Heat – Think of sunshine; Infrared waves radiate out from the walls and especially the glass door of the appliance in all directions.
- Convective Heat – Convective appliances have two walls, the firebox wall and a cabinet wall, between which air passes via convective currents or a blower delivering heated air to the room.
Starting the Fire
First off make sure you have good fuel. Fire staring is a crucial skill when it comes to wood burning. Not only are you staring the fire, you are “starting” the chimney properly so there is sufficient draft to produce a self-sustaining fire. I recommend starting with a Top Down Fire.
Non-Catalytic Appliance Operation
The goal with a non-cat stove is to maintain high efficiency by burning a hot fire where complete combustion is maintained with high fire temperatures. Heating this way with wood is a balancing act – maintaining an efficient fire while not overheating the space where the stove is located. This is best achieved by burning smaller hot fires, utilizing frequent reloading of the firebox with small loads of fuel with the air supply set somewhere between mid to fully open. If burning with the air supply fully open pay close attention for over-firing of the stove.
Catalytic Appliance Operation
While there are similarities between cat and non-cat stove operation there are significant, substantial and very important differences. Using methods for non- catalytic appliances with catalytic appliances can cause damage to the catalytic element, inefficient burning, excess fuel consumption, inadequate heat output and overall poor performance. Poor performance can lead to user frustration and unhappiness with the appliance.
The catalyst must achieve “light off” also called activation before being engaged. A good hot initial fire allowed to burn into a good bed of coals will generally achieve light off of the catalytic element. The best way to monitor catalytic combustor temperature is with a probe thermometer – new catalytic stoves are required to have probe thermometers at the catalyst.
Here’s how it works
Catalytic stoves have a bypass damper – when open the smoke and flue gases bypass the catalyst and go directly up the flue, when closed the smoke and flue gases are routed through the catalyst.
The bypass door must be open during start up to preheat the flue and establish draft. Once the stove is going and the catalytic combustor has reached 1,000°-1,600° the bypass damper should be closed. Closing the bypass to early during stove startup will prevent proper draft, and fail to light off the catalyst. Whenever the stove door is opened to reload the firebox the bypass door should be opened to prevent smoke spilling in to the living area.
With light off achieved and catalytic element temperatures from 650° to 1,400° the cat is under normal operating temperatures and fully active. Temperatures in excess of 1,600 dangerously overheating the cat and can seriously damage the element.
An active catalytic combustor triggers a chemical reaction in wood smoke that breaks apart the molecular structures of unburned particles. The catalyst converts smoke into water vapor, carbon dioxide, and heat – the elements of complete combustion.
With an activated catalyst the appliance has the best efficiency at low to moderate burn rates. The air controls should be closed more than non-catalytic appliances –less air into the appliance means a slower velocity of gases passing through the catalytic combustor. This means maximum efficiency and heat output. Catalytic appliances operate best at low and moderate burn rates because residence time is increased. This is unlike non-catalytic appliances which are more efficient at moderate to high burn rates.
- Load a catalytic appliance fully and burn the fuel load completely until there is a good bed of coals left for the next fuel load.
- Avoid small fuel loads and unnecessary door openings.
- Burning out and restarting catalytic appliances is not as preferable as it is with non-catalytic appliances.
Above all close attention to manufacturers’ operation instructions is important.