Ignition sequence and electrode tip geometry for oil-fired furnace

Abstract

The ignition sequence of a conventional oil-fired furnace is altered to achieve significant fuel economy. In response to a thermostatic call for heat, a short two to five second delay interval ensues during which the ignition electrode pair are energized to cause an arc which associates with the nozzle surface to burn off unburned fuel debris and, in effect, clean the nozzle, electrode tips and warm the spark. At the termination of this short interval, the oil pump and air blower are energized to achieve combustion of oil mist and air within an association ignition chamber.

1 . The method for operating an oil-fired furnace incorporating a nozzle, a motor-driven fan, an oil pump, an electrode pair extending to mutually spaced tips, and a controllable response to a thermostat call for heat to commence an ignition sequence, comprising the steps:
 (a) providing said electrodes with a tip geometry effective when energized to burn off unburned fuel debris at the nozzle;   (b) responding at said controller to a said thermostat call for heat to energize said electrode pair; and   (c) then energizing said motor driven oil pump and fan only after a delay effective to permit the energized electrode pair to burn off unburned fuel debris from the nozzle.   
   
   
       2 . The method of  claim 1  in which:
 step (a) provides the electrode tip geometry such that, at least during said step (c), delay an arc is caused to pass about the surface of the nozzle between the tips.   
   
   
       3 . The method of  claim 1  in which:
 step (a) provides the electrode tip geometry as mutually spacing the tips about ¼ inch apart.   
   
   
       4 . The method of  claim 1  in which:
 step (a) provides the electrode tip geometry as spacing each tip about ¼ inch above the orifice of the nozzle.   
   
   
       5 . The method of  claim 1  further comprising the steps:
 (d) simultaneously with step (b) commencing to monitor for the presence of fuel ignition for an ignition monitoring interval; and   (e) subsequent to step (c) at the termination of the monitoring interval and in the absence of fuel combustion, terminating steps (b) through (d).   
   
   
       6 . The method of  claim 1  in which:
 step (c) energizes said motor driven oil pump and fan following a said delay of about 2 to 5 seconds.   
   
   
       7 . An oil-fired furnace system, comprising:
 a combustion chamber;   a nozzle having an orifice for expelling oil mist into the combustion chamber;   an electrode pair having a tip geometry effective, when energized to burn off unburned fuel debris at the nozzle;   a fan assembly actuable to blow air into the combustion chamber;   an oil pump actuable to pump fuel oil from a source through the nozzle surface;   a controller assembly including one or more relays actuable to simultaneously energize the fan assembly and oil pump, an ignition transformer circuit energizable to effect creation of an arc between the electrode tips, and a delay circuit actuable to effect a delay output following a delay interval, said controller assembly being responsive to a thermostat call for heat to energize said ignition transformer circuit and simultaneously actuate said delay circuit and responsive to said delay output following a delay interval effective to cause said electrode pair to burn off unburned fuel debris at the nozzle, to simultaneously actuate said fan assembly and said oil pump.   
   
   
       8 . The system of  claim 7  in which:
 said electrode pair tip geometry is configured such that, at least during the delay interval, an arc is caused to pass about the surface of the nozzle.   
   
   
       9 . The system of  claim 7  in which:
 said electrode pair tip geometry is configured to mutually space the tips about ¼ inch apart.   
   
   
       10 . The system of  claim 7  in which:
 said electrode pair tip geometry is configured to space each said tip about ¼ inch above the nozzle orifice.   
   
   
       11 . The system of  claim 7  in which:
 said delay circuit delay interval is about 2 to 5 seconds.   
   
   
       12 . The system of  claim 7  in which:
 said electrode tip geometry is configured to space each tip about 1/16 inch forwardly from the forward surface of the nozzle.