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271015-UUM-A-0407
Unitary Products Group 9
FIGURE 7: Furnace Control Event Schedule
W2 SIGNAL
ON
CLOSED
OPEN
OPEN
CLOSED
ABSENT
PRESENT
HIGH INDUCER
HIGH STAGE PRESSURE
SWITCHAND 2ND STAGE
MAIN VALVE
CIRCULATOR HIGH
HEAT SPEED
2ND STAGE
CALL HIGH HEATAFTER LOW
HEAT IS ESTABLISHED
HIGH
HEAT
OFF
DELAY
30SEC.
HIGH LIMIT
W1 SIGNAL
LOW
INDUCER
LOW STAGE
PRESSURE
SWITCH
HSI
1ST STAGE
MAIN VALVE
FLAME
SENSE
LOW CIRCULATOR
HEAT SPEED
1ST STAGE
LOWPRESSURE
SWITCHCLOSE
RECOGNITION
HSI
WARM
UP
17SEC.
IGNITION
ACTIVATION
PERIOD
4SEC.
TRIALFOR
IGNITION
7SEC.
INTER-
PURGE
60SEC.
HSI
WARM
UP
27SEC.
IGNITION
DEACTIVATION
PERIOD
3SEC.
HEATFAN
DELAYON
30SEC.
BURN
TIME
POST
PURGE
15SEC.
HEATFANDELAYOFF
SELECTABLE
60,90,120,180SEC.
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
NOTE:
1. THIS DIAGRAM SHOWS TWO IGNITION ATTEMPTS
2. TIMING LENGTHS ARE NOT TO SCALE