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HVAC
Antifreezing Devices
1. Binary pressure switch
It is used to limit pressure conditions in a closed
refrigerant cycle for series / parallel logic.
High - Low Pressure Settings:
If the system
pressure reaches impermissible levels i.e. if the
pressure is less than 2 bar or if the pressure is higher
than 28 bar then the compressor is switched off. This
avoids its consequential damage.
2. Thermistor or Thermo sensor
It is a temperature sensing device, which protects the
AC systems from damage. It switches off the
compressor when condensed water tends to form ice
on the fins of evaporator. Thus it maintains the
evaporator temperature within a specified range.
A/C Relay
It controls the operation of compressor relay and
condenser fan motor according to the signals from
the switches which detects the state of the engine
and driving conditions.
A/C relay operates depending upon the state of
condition of following parameters:
(a) Idle speed control
(b) Dual pressure switch operation
NOTE:
If the pressure is less than 2 bar or if the pressure
is higher than 28 bar then the compressor gets
switched off.
(c) Coolant (water) temperature switch operation
(d) Thermistor (Evaporator thermal switch) operation
NOTE:
AC relay gets ON when the evaporative
temperature is above 5.5° C and it gets OFF when
the temperature is below 3.5° C.