Guardian 4721, Repair Manual

Page: 22 / 115

PART 1
GENERAL INFORMATION
SECTION 1.7
AUTOMATIC OPERATING PARAMETERS
Page 18
AUTOMATIC OPERATING SEQUENCES CHART
SEQ. CONDITION ACTION SENSOR, TIMER OR OTHER
1 “Utility” source voltage is No action Voltage Dropout Sensor on control
available. circuit board.
2 “Utility” voltage dropout below A 6-second timer on control Voltage Dropout Sensor and 6
60% of rated voltage occurs. board turns on. second timer on control board.
3 “Utility” voltage is still below 6-second timer runs for 6 Voltage Dropout Sensor and 6
60% of rated voltage. seconds, then stops. second timer.
4 “Utility” voltage is still low after Control board action energizes a Control board crank and run
6 seconds. crank relay and a run relay. The relays.
engine cranks for 7-9 seconds,
rests for 7-9 seconds, and so on
until engine starts. See NOTE 1.
5 “Utility” voltage still low and Control board’s “engine warmup Engine Warmup Timer (15 seconds)
the engine has started. timer” and “engine minimum run Minimum Run Timer (13 minutes)
timer” both turn on.
6 Engine running and “engine Control board action energizes a Control board transfer relay circuit
warmup timer” times out. transfer relay in transfer switch Transfer switch transfer relay.
and transfer to “Standby” occurs.
7 Engine running and load is No further action Control board’s “voltage pickup
powered by “Standby” power. sensor” continues to seek an
acceptable “Utility voltage.
8 “Utility” source voltage is Control board’s “voltage pickup Voltage Pickup Sensor (80%)
restored above 80% of rated sensor” reacts and a “return to Return to Utility Timer (10 seconds)
source voltage. utility timer” turns on.
9 “Utility voltage still high after 6 “Return to utility timer” times out Return to Utility Timer
seconds.
10 “Utility” voltage still high. Control board action opens the Control board transfer relay circuit
transfer relay circuit to ground. Transfer switch transfer relay.
Transfer relay de-energizes and
retransfer to “Utility” occurs.
11 Engine still running, loads are Control board’s “engine cooldown control board’s Engine Cooldown
powered by “Utility” source. timer” starts running. Timer (1 minute)
12 After 1 minute, “engine cooldown Engine Cooldown Timer
timer” stops and control board’s control board Run Relay.
run relay de-energizes. Engine
shuts down.
13 Engine is shut down, loads are No action. Voltage Dropout Sensor on control
powered by “Utility” source. circuit board.
Return to Sequence 1.
Note1: In Sequence 4, if engine has not started in 90 seconds cranking will end and shutdown will occur.