Burner control system

Burner control apparatus for use with a fuel burner installation having an operating control switch which is actuated to produce an ignition request signal, an air flow switch which provides an air flow signal to indicate the presence of an adequate air flow through the burner, and means responsive to said burner control apparatus for controlling fuel flow, said burner control apparatus comprising:

• an electronic timing circuit for providing an ignition cycle having successive timing intervals including in sequence a purge interval, a pilot ignition interval, a pilot stabilization interval and a main fuel ignition interval;
• air means for providing an air flow through the burner during said ignition cycle;
• lockout means, responsive to a lockout signal applied thereto for a predetermined time, for terminating burner operation and stopping fuel flow to said burner installation;
• means, responsive to said operating control switch, for activating said timing circuit, including:
• a first photocoupler having a light source connected in parallel with said air flow switch and providing an output signal across its output terminals when said air flow switch is open;
• a second photocoupler having a light source connected in series with said air flow switch and providing an output signal across its output terminals when said air flow switch is closed;
• means, operative in response to an ignition request signal, for initially applying power to the timing circuit to begin an ignition cycle only if said first photocoupler output signal is present;
• and
• means, operative in response to an ignition request signal, for applying a lockout signal to said lockout means until the occurrence of said second photocoupler output signal;
• whereby said timing circuit is disabled to prevent further ignition cycle operation if said air flow switch is closed before said air means is operative and said lockout means is actuated to prevent further ignition cycle operation if said air flow signal is not present within a predetermined time after said air means is operative.