Chip wood furnace and furnace retrofitting system

A new and improved furnace system for retrofitting a conventional domestic oil furnace to provide for automatic, continuous, and efficient burning of chipped, hogged, pelletized or other fragmented wood type fuel, said conventional oil fired furnace of the kind having oil fuel combustion chamber means and heat exchange means, said oil furnace having an oil burner gun inlet to the oil combustion chamber with the oil burner gun removed, said new furnace system comprising:

• wood fuel combustion chamber means formed by an enclosure of refractory material for combustion of the wood type fuel at elevated temperatures to substantially complete combustion, said enclosure formed with a primary combustion region and an afterburner region, a combustion grate positioned in the combustion region for receiving the fragments of wood type fuel and for supporting the combusting fuel, said enclosure formed with an opening at the top over the combustion grate for gravity delivery of fuel onto said grate, said enclosure formed with combustion air draft inlet means in the primary combustion region in the vicinity of the grate for introducing combustion air, and draft outlet means spaced from the grate in the afterburner region for venting the products of combustion;
• flame tube means for coupling the wood fuel combustion chamber outlet with the oil combustion chamber inlet of a conventional oil fired furnace, said flame tube adapted for extending into the oil combustion chamber of a conventional oil furnace with the oil burner gun removed, said flame tube means formed with selected length to afford substantially complete combustion of the exhaust gases while maintaining sufficient temperature to radiate heat into the oil combustion chamber and heat exchanger;
• wood type fuel fragment feeding means comprising conveyor means for trickle feeding wood fuel at selected uniform rates to a position over the wood fuel combustion chamber and the opening at the top of the chamber;
• substantially vertical passageway means for gravity feed of the wood fuel type fragments from the conveyor means through the top of the wood fuel combustion chamber to the combustion grate, said passageway means affording a first break in the fuel line thereby to prevent propogation of combustion up the fuel line from the combustion chamber into the wood fuel feeding means;
• blower means for inducing a forced draft through the wood fuel combustion chamber means, flame tube means, and conventional oil furnace combustion chamber and heat exchanger at least during start up of the furnace system;
• said wood type fuel combustion chamber means adapted to receive oil burner gun motor and firing means at the inlet of said wood fuel combustion chamber for igniting wood fuel type fragments on the combustion grate and initiating sustained combustion of wood fuel received upon and supported by the combustion grate during start up of the furnace system;
• and control means for controlling and sequencing said furnace system elements, said control means adapted to turn on the wood fuel trickle feeding means and induced draft blower means, and further fire the oil gun motor and firing means after the induced draft is established for igniting wood type fuel fragments received on the combustion grate, said control means adapted to turn off the oil gun motor and firing means once the wood type fuel is ignited and passing combustion heat through the system;
• and safety switch control means for shutting down the system if the oil burner gun fails to operate or ignite the wood type fuel, if the induced draft fan fails to operate during start-up, or if combustion heat climbs up the fuel feed passageway.

A new and improved furnace system for retrofitting a conventional domestic oil furnace for combustion of fragmented wood type fuel upon removal of the oil gun motor and igniter means from the conventional oil furnace comprising:

• wood fuel gun means comprising a refractory wood feed combustion chamber for efficient high temperature combustion of fragmented wood type fuels, fragmented wood type fuel feeding means for trickle feeding wood fuel fragments into the wood fuel combustion chamber at rates to produce upon combustion substantially the heat equivalence of the domestic oil burner gun motor and igniter means removed from a conventional oil furnace to be retrofitted, flame tube coupling means adapted for coupling combustion exhaust from the wood fuel combustion chamber into a conventional oil furnace to be retrofitted, said wood fuel combustion chamber adapted to receive the oil gun motor and igniter means removed from the conventional oil furnace for initiating combustion of wood type fuel in the wood fuel combustion chamber, means for forcing a draft through the wood fuel combustion chamber, and control means for controlling the fuel feeding means, forced draft means and the oil gun motor and igniter means of the conventional oil furnace to be retrofitted whereby said retrofitting furnace system affords automatic and continuous combustion and heat delivery from wood fuel fragments at rates comparable to the preretrofitted conventional oil burning furnace system.

A new and improved retrofitted furnace system, for combustion of wood type fuel fragments comprising:

• conventional oil furnace means comprising oil combustion chamber means, heat exchanger means and oil gun motor and igniter means, said oil gun motor and igniter means removed from its mounting position at the oil combustion chamber;
• wood fuel gun means comprising refractory wood fuel combustion chamber means for efficient and high temperature combustion of fragmented wood type fuels, fragmented wood type fuel feeding means for trickle feeding wood fuel fragments into the wood fuel combustion chamber at rates to produce upon combustion substantially the heat equivalence of said oil gun motor and igniter means, flame tube coupling means adapted for coupling combustion exhaust from the wood fuel combustion chamber into the oil combustion chamber of the retrofitted oil fired furnace, said wood fuel combustion chamber constructed and arranged for receiving the oil gun motor and igniter means for initiating combustion of wood type fuel in the wood fuel combustion chamber, and means for forcing a draft through the wood fuel combustion chamber;
• said oil gun motor and igniter means mounted in the wood fuel combustion chamber for initiating combustion of wood type fuels in said combustion chamber;
• and control means for controlling the wood type fuel feeding means, forced draft means, and oil gun motor and igniter means whereby said retrofitted furnace system affords automatic and continuous combustion and heat delivery from wood fuel fragments at rates comparable to the pre-retrofitted conventional oil furnace.

A new and improved residential scale furnace system for providing automatic, continuous, and efficient burning of chipped, hogged, pelletized or other fragmented wood type fuel, said furnace system comprising:

• heat exchange plenum means having an inlet for receiving hot combustion gases and a chimney flue outlet, said heat exchange plenum adapted for transferring heat of combustion gases to a heat transfer medium;
• wood fuel combustion chamber means formed by an enclosure of refractory material for combustion of the wood type fuel at elevated temperatures to substantially complete combustion, said enclosure formed with a primary combustion region and an afterburner region, a combustion grate positioned in the combustion region for receiving the fragments of wood type fuel and for supporting the combusting fuel, said enclosure formed with an opening at the top over the combustion grate for gravity delivery of fuel onto said grate, said enclosure formed with combustion air draft inlet means in the primary combustion region in the vicinity of the grate for introducing combustion air, and draft outlet means spaced from the grate in the afterburner region for venting the products of combustion;
• flame tube couplnng means for coupling the wood fuel combustion chamber outlet with the heat exchange plenum means inlet, said flame tube adapted for extending into the heat exchange plenum means, said flame tube coupling means formed with selected length sufficient to afford substantially complete combustion of the exhaust gases while maintaining sufficient temperature to radiate heat into the heat exchange plenum;
• wood type fuel fragment feeding means comprising conveyor means for trickle feeding wood fuel at selected uniform rates to a position over the wood fuel combustion chamber and the opening at the top of the chamber;
• substantially vertical passageway means for gravity feed of the wood fuel type fragments from the conveyor means through the top of the wood fuel combustion chamber to the combustion grate, said passageway means affording at least a first break in the fuel line thereby to prevent propogation of combustion up the fuel line from the combustion chamber into the wood fuel feeding means;
• blower means for inducing a forced draft through the wood fuel combustion chamber means, flame tube means, and heat exchange plenum means at least during start up of the furnace system;
• said wood type fuel combustion chamber means adapted to receive oil burner gun motor and firing means at the inlet of said wood fuel combustion chamber for igniting wood fuel type fragments on the combustion grate and initiating sustained combustion of wood fuel received upon and supported by the combustion grate during start up of the furnace system;
• control means for controlling and sequencing said furnace system elements, said control means adapted to turn on the wood fuel trickle feeding means and induced draft blower means, and further fire the oil gun motor and firing means after the induced draft is established for igniting wood type fuel fragments received on the combustion grate, said control means adapted to turn off the oil gun motor and firing means once the wood type fuel is ignited and delivery combustion heat through the system;
• and safety switch control means for shutting down the system if the oil burner gun fails to operate or ignite the wood type fuel, if the induced draft fan fails to operate during start-up, or if excessive combustion heat climbs up the fuel feed passageway.