Ingersoll-Rand 900829, Руководство по обслуживанию

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General Description
28
Heat Mode - Model 30 and 50 Units
Only
The unit enters Heat mode when the temperature
falls a pre-determined number of degrees below
the setpoint temperature. Before going into the
Heat mode, the controller places the unit the Null
mode for 10 seconds and then the Purge mode for
45 seconds before shifting to the Heat mode.
NOTE: The unit only uses the Purge mode
before the Heat mode the first time the unit goes
into Heat. After that the Purge mode is not used
before the Heat mode unless the unit is powering
up or when going directly from the Cool mode to
the Heat mode.
To shift to the Heat mode the controller energizes
the compressor clutch, evaporator fans, defrost
solenoid, condenser blocking solenoid, and hot
gas heat relay, which energizes the liquid injection
valve.
The refrigerant flow in Heat mode is similar to a
conventional hot gas heat cycle in a T-Series truck
unit. The condenser blocking solenoid is closed
and the defrost solenoid is open so high pressure
refrigerant vapor leaves the compressor and flows
through the defrost line, defrost solenoid, and
drain pan heater to the evaporator. There, the
refrigerant heats the evaporator and returns to the
compressor through the accumulator, CPR, and
suction lines. The liquid injection valve is open so
refrigerant in the condenser will flow through the
liquid injection valve into the suction line when
the pressure in the condenser is higher than the
pressure in the suction line.
The unit operates in Heat mode until the setpoint
temperature is reached. The unit then enters Null
mode.
• If the temperature falls a pre-determined
number of degrees, the unit will go into Purge
mode for 45 seconds and then go into Heat
mode.
• If the temperature rises a pre-determined
number of degrees, the unit will go into Cool
mode.
NOTE: The following diagram shows a Model
30 unit. Heat mode in a Model 50 unit is similar.
Figure 7: Model 30 Refrigerant Flow in Heat and Defrost Modes
HEAT/DEFROST MODE
CONDENSER BLOCKING SOLENOID (PS5)
ARA1808
COOL/PURGE MODE
ARA2042
CONDENSER BLOCKING SOLENOID