The present invention relates to a condensing furnace utilizing a pulsating combustion process which furnace discharges flue products consisting of flue gas and condensate through a flue gas conduit and more particularly, this invention relates to a drain leg assembly connected to the flue gas conduit for separating the flue gas and condensate received from the condensing furnace and discharging them separately and independently through a flue gas vent and a drain line, respectively.
The pulsating combustion process has recently been adapted for residential gas fired furnaces. In a pulsating combustion condensing furnace, recently introduced by Lennox Industries Inc. and identified as the G14 series, the combustion process takes place in an enclosed combustion chamber. Basically, gas and air enter the combustion chamber via flapper control valves and mix in the combustion chamber. To start the combustion cycle, a spark is used to ignite the gas and air mixture. Positive pressure from the combustion process within the combustion chamber closes the flapper control valves and forces combustion products (exhaust gas) down a tail pipe extending from the combustion chamber. Exhaust gases leaving the combustion chamber create a negative pressure. This opens the flapper control valves drawing gas and air into the combustion chamber. At the same instance, part of the pressure pulse is reflected back from the tail pipe into the combustion chamber causing the new gas and air mixture to ignite. No spark is needed for the second ignition. The process repeats itself without continued use of the spark plug or purge air blower. The steps of opening the flapper control valves to draw the air/gas mixture into the combustion chambers and of igniting them are repeated 58 to 68 times per second forming consecutive pulses of one-quarter to one-half Btu (British thermal unit) each. Only about 0.0003 cubic feet of natural gas is consumed for each ignition. From the tail pipe, the exhaust gases pass to an exhaust decoupler, which is part of the sound reduction system of the condensing furnace. In the exhaust decoupler, the gases are cooled from about 700.degree. Fahrenheit to 350.degree. Fahrenheit. The exhaust gases from the exhaust decoupler are forced through a condenser coil and are discharged through the flue gas outlet from the condensing furnace. Exhaust gases passing through the condenser coil are cooled by air passing over the coil so that the exhaust gas will leave at a relatively low temperature, such as 100.degree. Fahrenheit or lower. As the temperature of the gases reach dew point (at about 130.degree. Fahrenheit) in the condenser coil, water is condensed from the gases, allowing the furnace to reclaim the latent heat of combustion. High furnace efficiencies in excess of 91 percent can be achieved in condensing furnaces of the type described.
The flue products, which consist of small amounts of spent exhaust gases and condensate are expelled through a flue gas conduit from the condensing furnace. In tests, it has been found that an 80,000 Btu input residential condensing furnace produces approximately five gallons of condensate per day under normal operation in winter. In development of the residential condensing furnace, it was determined that it was necessary to develop means for efficiently and effectively handling the passage of flue gases and condensate from the condensing furnace in separate flow paths. Whereas it was ascertained that condensate could be discharged to a conventional drain, the flue gas could not safely be discharged into a conventional drain or inhabited environs.
An object of the present invention is to provide a drip leg assembly for effectively and efficiently separating the flue gases from the condensate discharged from a condensing furnace.
Another object of the present invention is to provide a drain leg assembly for a condensing furnace, the drain leg assembly being connected to a flue gas conduit means and including a tubular body having inlet means communicating with the flue gas conduit means, flue gas outlet means connected to the flue gas vent and condensate outlet means connected to a drain line, whereby flue gas and condensate are separately discharged from the flue gas vent and the drain line, respectively.
Other objects and advantages of the present invention will become more apparent hereinafter.