|Finnish Contraflow Heat-Kit
The Heat-Kit system was developed in 1985. It is a system of precast refractory components that has allowed us to reduce the amount of expensive on-site time required to build a heater core by 90% . The main innovation was to retain about 50% of the firebrick construction in the core, including all critical areas such as the firebox. Firebrick are unsurpassed, in our opinion, for taking the heavy abuse of thermal cycling.
Gas flow through the Heat-Kit is illustrated below. It is shown with the bakeoven option.
Outside combustion air enters at a lower level through the foundation. It passes through the air damper (1) and then into the firebox (2). Rapid combustion of the fuel charge results in long flames, which are directed around the bakeoven and then burn out in the secondary combustion chamber. The hot gases are cooled in two downdraft heat exchange channels (7) and enter a connecting plenum (8) under the firebox. From there the cooled exhaust gases enter the chimney at floor level. The design of the connecting plenum allows the chimney to be connected anywhere at the back or side of the heater without unbalancing the downdraft channels.
A shutoff damper (9) in the chimney is closed once the fire is completely out, after about two hours. This interrupts the chimney draft and prevents the large amount of energy now stored in the masonry from bleeding out through the flue.
The design has been refined
over several years of trials and feedback from users. It is no longer simply an
add-on feature. Instead, we have redesigned the whole heater around it.
The oven operates at zero cost, since you are firing the heater daily to heat your home. It can be on either side (front or back). A popular design is to have the heater serve as a space divider between living room and kitchen, with the glass firebox doors on the living room side and the oven on the kitchen side.
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