The control continually compares the set temp to the actual water temp. When
the water temp is 1º below the set point the following sequence starts:
1. The control checks for open blower vacuum switch
2. Blower starts pre-purge cycle as the ignitor heats up (20 Sec).
3. The control checks for a closed blower vacuum switch.
4. At proper ignitor temp, a 4 second trial begins. Gas valve opens and
monitors flame sense. The blower will turn off for one second. The ignitor
is de-energized at flame sense or at completion of 4 sec trial. If the flame is
sensed, The blower vacuum switch, control loop, temp sensor & flame
sensor are constantly monitored during call for heat.
5. When set temp is reached, the control ends the call for heat. The gas valve
is de-energized, and the flame is extinguished.
6. The blower will operate for a 30 second post purge.
7
UHS Sequence of Operation: Normal
NOTE: If during step four, the heater fails to fire, please procced to the next page for
more details outlining failure to light operations.
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