Jacks are one tough furnace. The fireboxes are made of 7-gauge (3/16 inch thick) steel. That's heavy duty. The firebox is cylindrical (round). It is near impossible for it to warp or burn out. They have an extra heavy-duty cast iron grate and are lined with 9-inch high firebrick. They are not to be compared to the lightweights from your local discount store. They cost a little more, but they don't have to be replaced every few years like the lightweights. Jack furnaces have been made since 1976. No one has ever requested a firebox replacement because it failed.
Jacks operate on a forced draft principle. Put some kindling in, light it with a match, and turn the thermostat up. That turns on the combustion fan to get the wood burning. Then load it up and relax. It's automatic from there. The room thermostat tells the combustion fan to start when it is not warm enough and shuts it off when you're comfortable.
A fan control mounted in the sheet metal plenum above the firebox tells the circulating blower when to start and stop. All automatically.
Is the Jack efficient? You bet. The right amount of the air from the combustion fan is directed to the fire. Twenty per cent of the air (called secondary air) is directed above the fire to ignite the unburned gases and smoke created by the main fire. The result is high efficiency wood burning. |
