Furnace Combustion And Safety
The regulator [A] maintains stable gas pressure over full range of required gas flow. A programmable controller [B] reads one of two Type-R thermocouples © and activates an actuator motor [D] which opens/closes the automatic butterfly valve [E]. As the air pressure changes, the proportionator [F] proportionally adjusts the gas flow. The ALO valve ® provides high-fire gas adjustment. Safety: Flame monitoring unit [G] energizes spark ignition transformer [H] only after purging the atmosphere inside the furnace with fresh air. It then initiates a trial-for-ignition period of 15 seconds during which the spark plug [I] (standard) fires and the main gas valves allow gas flow to the burner. If the U.V. Scanner [J] sees a flame, the valves stay open and the spark plug is de-energized. Otherwise the valves close and a manual reset is required. The Redundant Automatic Shutoff Valves [K] or DMV-DLE (mandatory on furnaces over 150KBTU/HR) shut off the gas immediately if any of the following incidents occur: