Abstract:
An oil burner control system is disclosed in which recycling between a loss of combustion to re-establishment of combustion is limited by counting the number of times recycling occurs and causing a the system to stop recycling and go to lockout after the count reaches a predetermined value.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to oil burners and more particularly to an oil burner system that will prevent or reduce problems such as soot accumulation due to unlimited recycling under inadequate combustion conditions. 
     2. Description of the Prior Art 
     In our co-pending patent application entitled “Pump Purge for Oil Primary”, Ser. No. 09/621,257 filed and Jul. 21, 2000 assigned to the assignee of the present invention, an oil burner system which provides hardware and software that allows the system to be quickly primed or purged when necessary without entering a number of unwanted lockouts is described and claimed. In the normal operation of that system, after “Power On” occurs and various checks are made, an “Idle State” is entered where the system awaits a “call for heat” from a thermostat. When this arrives, a controller starts the ignition process, the flame is established and the system goes to a normal “Run State” in which the furnace supplies heat until the call for heat from the thermostat disappears. Sometimes in the normal Run State, the flame can go out before the call for heat from the thermostat ends. This is usually caused by a transitory condition such as an air bubble in the fuel line. When the flame in the burner goes out after having been established and before the thermostat stops calling for heat, the system goes into a “Recycle State” which, after a delay (recycle time), the system reverts to the Idle State where it receives the continued call for heat from the thermostat and the controller starts the ignition process and again initiates a flame. The system then returns to its normal Run State. Unfortunately, the condition causing the flame out may not have disappeared; for example when the system does not support combustion after the igniter turns off. When this occurs, the flame will again extinguish putting the system back in the Recycle State again and an endless cycle to the Run State, the Recycle State, the Idle State etc. may occur. This endless recycling is often due to a poor combustion situation and thus excessive soot may develop, excessive wear on components may result, and other damage may occur. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention overcomes the above problems by providing a recycle limit on the number of times that the system can recycle during a predetermined period. 
     This is accomplished with a recycle timer and logic for the microprocessor in the Primary Control so that the oil burner is restricted to going through the recycle mode a predetermined number of times (for example three), unless the call for heat is satisfied or power is removed. If the system enters the Recycle State more than the predetermined number of times it will go into a “Lockout State” that requires manual intervention to reset the control. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing the burner control system of the above mentioned co-pending application; 
     FIG. 2 is a state diagram showing various states of operation of the system of FIG. 1; and 
     FIG. 3, is a flow diagram for the logic used in the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1, an oil burner  10  is shown having a blower  12  in the lower portion thereof and a spark igniter  14  in the upper portion there of. A pump  16  is shown attached to the blower  12  and a supply conduit  18  connects pump  16  to a valve  19  that is connected to a source of oil (not shown). A motor  20 , which operates blower  12  to produce a stream of air, is shown also attached to pump  16 . Pump  16  is operable by motor  20  to pump a fine mist of oil combined with the stream of air through blower  12  and into a combustion chamber  24  of a furnace (not shown). The spark igniter  14  employs a pair of spark electrodes  26  which, when energized, produce a spark across the gap therebetween to ignite the mist of oil and swirl the burning fuel into the combustion chamber  24  where the heat generated will be circulated to the area to be heated. A flame detector such as a cad cell  28  views the combustion area to determine whether or not ignition has occurred and sends a signal indicative thereof via lines  29  to a primary controller  30  and an indicator light  31 . 
     The primary controller  30  is shown receiving signals from a thermostat  32  over lines  34 , and acts to control the operation of the oil burner  10 . More particularly, when thermostat  32  sends a signal calling for more heat, primary controller  30  sends a signal from terminals  40  over lines  41  to the spark igniter  14  that then operates to produce a spark across the gap between electrodes  26 . Primary controller  30  also sends a signal from terminals  44  via lines  45  to energize motor  20  and pump  16  to start the mist of oil and air flowing from the blower  12  to combustion chamber  14 . If the oil and air are present and the spark ignites the oil, then the flame detector  28  provides a signal via lines  29  to controller  30  and light  31  to show that satisfactory operation has occurred. Thereafter, when the flame is determined to be self sustaining, the spark igniter  14  is turned off and the furnace produces heat until the call for heat is lost, and the motor  20 , blower  12  and pump  16  are shut off. 
     It should be understood that controller  30  contains, among other things, a RAM, a ROM, at least a portion of which is non-volatile, an EEPROM for storing values to be utilized in timing etc. and a plurality of DIP switches for storing certain predetermined constant values to be used. Also, in FIG. 1 is a reset button  50  which will be described below and a remote alarm  60  connected to the primary controller  30  by lines  62  for purposes of producing an alarm (for example to the home security system) that can alert that a problem has occurred in the system and that service should be performed as will be further explained below. 
     FIG. 2 shows the various states that can be occupied by the system of FIG. 1. A simplified explanation of FIG. 2 is as follows: 
     Upon “Power up”, State  1 , shown by box  70 , the primary controller  30  performs checks to verify that conditions which would preclude proper system are not present. The system then goes to Idle, State  2 , shown by box  74 , where it waits for a call for heat from thermostat  32 . Upon receiving a call for heat, the system moves to Valve On Delay, State  3 , shown by box  78 , where the controller  30  performs certain safety checks, determines that there is currently no flame and then starts a timer to delay the opening of valve  19  until after motor  20  and igniter  14  are on. Upon completion of the timer, the system moves to Trial For Ignition, State  4 , shown by box  82 , where the controller  30  opens valve  19  and a stream of oil and air passes the igniter electrodes  26 . When the flame is detected by cad cell  28  and a signal indicative thereof is sent to controller  30 , the system moves to Carryover, State  5 , shown by box  86 , where another short delay occurs to assure that the flame is self sustaining at which time the igniter is extinguished and the system moves to an normal Run, State  6 , shown by box  90 , where heating continues until the call for heat is lost. When this occurs, the system moves to Blower Off Delay, State  7 , shown by box  94 , where the valve  19  is turned off and a timer allows the motor  20  to remain on a short time while the hot air is pushed through and out of the system. When this is done, the system returns to Idle, State  2  where it again waits for a call for heat. 
     In the event that the burner  10  is just being installed or has undergone extensive maintenance, the oil supply lines and filter may be dry in which case, the above procedure could result in a “no flame” condition at Trial For Ignition, State  4  and, after a delay, the system would go to Lockout, State  9 , shown by box  98  where further operation is prevented until the reset button  50  is pushed which allows the procedure to start over again. However, this is permitted to occur only a predetermined number of times, for example twice, after which the system goes into a restricted lockout and cannot again be started by merely pushing the reset button  50 . In order for a technician to get out of restricted lockout, the system provides that the reset button  50  can be pushed and held for an extended period, for example, 30 seconds, after which the system returns to the normal operation again. In order for the technician to avoid having to wait through several lockouts during an initial start up, the system allows the reset button to be pushed during States  3 - 5  (as long as there have been no previous lockouts since that last successful run) and the timing in State  4  is then increased to a value sufficient for the oil to fill the conduits and the filter and flame to be established. After the longer delay in State  4 , the detection of flame would move the system to State  5 , as before, and operation would continue as above described. 
     A more detailed description of the various States and their function may be had by referring the above-mentioned co-pending application. 
     If the system is operating in State  6 , with the sustained flame heating the desired area, and the flame is lost, control goes to a Recycle, State  8 , shown by box  102 . In State  8 , the system has had a proven flame that has subsequently gone out before the thermostat has indicated no further heat is needed. When this happens, the Recycle State  8  writes the state value to EEPROM. The blower motor, igniter and oil valve are turned off. The recycle timer (for example 60 seconds) is started and the indicator light  31  is flashed slowly to provide an indication that the system is in Recycle State. When the recycle timer expires, the indicator light  31  is turned off and the system goes back to the Idle State  2 . 
     As mentioned above, the call for heat from thermostat  32  causes the system to repeat the sequence leading up to the Run, State  6 . In the event that the flame goes out again, the same cycle is repeated. In order for the system to prevent endless repetition of the Recycle, State  8 , and to prevent damage to the system and the area being heated, the present invention provides a limit on the number of time the recycle can occur. After this limit is reached, the system goes to Lockout, State  9 , which prevents further operation until manual intervention occurs. 
     Referring to FIG. 3, the logic diagram for the present invention is shown and, it will be assumed that the system of the above mentioned co-pending application is in Run, State  6  of FIG.  2 . While in Run, State  6 , the system continually checks the flame and the call for heat. The procedure is shown starting with an arrow  120  in FIG.  3 . The existence of a flame is checked as shown by diamond box  124 . If there is no loss of flame, the answer is “no” as seen by arrow  128  and the system moves to diamond box  132  where the determination is made as to whether there has been a loss of a call for heat from thermostat  32 . If the answer is “no”, the system returns back to arrow  120  and diamond box  124  as shown by arrow  136 . This cycle continues as long as there is flame and a call for heat. If there has been a loss of the call for heat, the answer, at diamond box  132  is “yes” and the system moves to box  140 , as shown by arrow  144 , where the recycle counter is cleared. Then, the system moves on to box  146 , Blower off delay as shown by arrow  148 . Blower off delay, box  146  corresponds to State  7  in FIG. 2 and, after the delay, the system moves, as shown by arrow  150 , to Idle, box  152 , which corresponds to State  2  of FIG.  2 . As described above, when another call for heat from thermostat  32  is received, the system of FIG. 2 moves, to Valve On Delay, State  3 , Trial For Ignition, State  4 , and to Carry Over, State  5  to re-establish Run, State  6 . This puts the system back at arrow  120  in FIG.  3 . 
     If, in diamond box  124 , it is determined that there is a loss of flame, the answer is “yes” and the system moves from diamond box  124  to box  160 , as shown by arrow  164 . At this position, the recycle counter is incremented by 1 and, the system moves, as shown by arrow  168 , to diamond box  172 , where a determination is made as to whether more or less than the predetermined number of recycles have occurred (in this case, three). If less than three, the system moves, as shown by arrow  176  to box  180  where a predetermined delay (in this case, sixty seconds) is introduced to allow cooling of the system and expulsion of combustion products and uncombusted fuel before attempting to restart the system. After the delay, the system moves to Idle, box  152  as seen by arrow  184 , which, as explained above, is the same as Idle, State  2 , box in FIG.  2 . Thereafter, the system moves through Valve on Delay, State  3 , Trial for Ignition State  4 , and Carry Over, State  5  to Run, State  6 . This, again, puts the system back to arrow  120  of FIG.  3 . 
     In diamond box  172 , if there have been three or more recycles, the system moves, as shown by arrow  188  to Lockout, box  192  where the recycle counter is cleared and the system is put in the Lockout condition, i.e., State  9  in FIG.  2 . Thereafter the system will resume normal lockout operation explained above. After the reset button  50  is pushed system re-ignition may again occur and the process repeated as above until the flame stays on, the call for heat is lost or the return to Lockout, State  9 , box  98 , again occurs. 
     It is therefore seen that we have provided a limit for a burner system to prevent excessive recycling when a loss of flame occurs after having been established. Many changes and modifications will occur to those having ordinary skill in the art and we do not wish to be limited to the specific disclosures used in describing the preferred embodiment. For example, it will be understood that while the present invention has been shown to operate the oil-fired burner of a furnace, the invention may be used with boilers, water heaters and other equipment. Also, where a thermostat  32  has been shown to provide the call for heat, an Aquastat® or other heat detecting device may be employed. The number of recycles may be more or less than three and the recycle delay may be other than sixty seconds. Furthermore, many of the logic sequences disclosed may be considered optional and alternate sequences may be utilized. 
     The scope of the invention is set forth in the claims appended hereto.