Lochinvar CF-CH(E)-i&s-08, 999 - 750, 399 Ignition, Heat Transfer Process, Post-Purge, Idle

Installation and

Service Manual

are energized. This does not interfere with the safety functionality of either pressure switch or the ignition modules.

IGNITION

(Ignition Module Function)

Once the trial for ignition period has been completed, the ignition module sends 24VAC to the gas valves on one or the other of the primary stages . Gas valves should open and allow gas to flow to the burners in the stages being energized. The fuel/air mixture should ignite from the hot surface igniter. Once this voltage has been sent to the valves, the hot surface igniter is turned off. The ignition module then monitors the status of the flame and will either allow ignition to continue or shut down the gas valves should flame not be proven and proceed to a Flame Failure condition. If flame was proven briefly during the ignition period, the module may not proceed to Flame Failure, but rather post- purge and then go into another trial for ignition.

HEAT TRANSFER PROCESS

(Gas Valves, Burner and Heat Exchanger)

Once flame has been proven, the ignition module will hold the gas valves open as long as there is proof of flame and a call for heat is present. Depending upon the number of stages being called upon by the electronic thermostat controller, more or less B.T.U.’s are delivered to the water within the heat exchanger. Once the temperature rise is sufficient to allow stages to be turned off, the electronic thermostat will begin to shut down stages in preprogrammed order to prevent the set point from being exceeded. When the temperature of the water reaches that of the highest programmed set point, all stages will be shut down.

POST-PURGE

(Ignition Module Function) When 24VAC is removed from the ignition module’s thermostat input, the module turns off the gas valves and maintains the blowers for approximately 25 seconds in order to allow the combustion chamber to be purged of all combustion by-products.

IDLE

(Electronic Thermostat Function)

After completion of the post-purge cycle, the unit will go into an idle state whereby the electronic thermostat continuously monitors the water temperature until the water temperature drops to levels that require additional heat.

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