Carrier Supra 950MT Operation & Service Manual

Also see for SUPRA 950Mt: Operation and service manual Operator's manual

3-23 62-11863b. Auto Start Sequence (Engine Mode)On initial power up, there is a five-second delay before the starting sequence begins. When starting conditions aremet, the start sequence begins by energizing the run relay, defrost relay, main heat relay, all hot gas and coolrelays, and the unloader.If the required glow time is zero, the control will energize the starter after a five-second delay. After five seconds, theglow plug relay (GPR) is energized by a timed run control relay (RCR), supplying power to the glow plugs. The starteris energized after the variable glow time has elapsed, which is based on engine coolant temperature that is monitoredby the microprocessor.The flash circuit is used to ensure current is always available in the windings of the motor. This current is used toexcite the magnetic field the motor produces when turned by the engine. The current is driven by three capacitorsthat are uniquely sized and balanced for the system. These capacitors work in conjunction with the motor to ensurethree-phase AC voltage.The engine will crank for 10 seconds or until engine operation is sensed by the alternator auxiliary signal. If theengine fails to start, a 15-second null cycle will elapse before subsequent start attempts.The run relay remains energized until the next starting sequence. Before the next starting sequence, the oil pres-sure and alternator auxiliary output must be checked to ensure that the engine is not running.For the second and third start attempts, the glow time is increased by five seconds over the glow time of the firstattempt listed below. The control allows three consecutive start attempts before the starting is locked out and thestart failure alarm is activated.c. Variable Glow TimeThe glow time for the first start attempt varies in duration based on engine coolant temperature and the type ofengine selected.The second and third start attempts have a glow time that is five seconds greater than the table amount. The glowtime can be manually overridden through the function parameters. If the coolant temperature sensor is defective,the control assumes a temperature of less than 32°F (0°C) for the glow timing.d. Minimum On-TimeIf configured for Start-Stop operation, the unit must run for the minimum runtime (factory default is four minutes)before it can consider shutting off. This time is necessary to prevent short-cycling and ensure adequate air flowthrough the load to allow the micro to accurately sense load temperature and bring the battery up to minimum volt-age level.Minimum on-time value is selected via keypad.e. Minimum Off-TimeOnce the unit has cycled off, it will remain off for the minimum off-time (factory default is 20 minutes). This preventsrapid cycling due to changes in air temperature. Air temperature in the box can change rapidly, but it takes time forthe product temperature to change.Minimum off-time value is selected via keypad.The minimum off-time is overridden if the temperature is more than ±11°F (±6°C) from set point.f. Time Start / Temp StartSelection between Time Start or Temp Start is provided via the keypad• Temp Start: Unit remains OFF until box temperature deviates from set point.• Time Start: Unit restarts automatically 30 minutes after it has stopped regardless of the box temperature.Table 3–8 Engine Coolant Temperature Glow TimeTemperature TV DILess than 32°F (0°C) 15 5533°F to 50°F (1°C to 10°C) 10 4051°F to 77°F (11°C to 25°C) 5 25Greater than 78°F (26°C) 0 10