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TM5-4120-387-14
b.
Bypass cycle.
This unit has a bypass cycle which allows cooling operation
at low cooling loads without cycling the compressor (1) on and off.
In bypass,
the refrigerant is piped from the discharge (high side) to the suction (low side)
of the compressor, bypassing the evaporator coil (10).
When the temperature control thermostat on the control panel senses that
cooling conditions have reached the set point, it closes the liquid line solenoid
valve (6) to shut off refrigerant flow to the evaporator coil (10).
As the compressor suction pressure starts to drop, the hot gas solenoid
valve (9) closes and the pressure regulating valve (12) opens to allow flow of hot
gas from the compressor.
The expansion valve (quench) (11) senses the temperature of the gas at
the suction side of the compressor.
To prevent excessively hot gas from reaching
the compressor, the expansion valve (quench) (11) opens to allow liquid
refrigerant to mix with the hot gas.
The charging valves (13) are provided for charging, and general servicing
of the high and low pressure sides of the refrigerant system.
The pressure switch (low) (14), the pressure switch (high) (15), and the
pressure relief valve (4) are provided to protect the unit from damage due to
pressure extremes.
The pressure control switch (16) overrides the fan speed control switch
to place the fan in either HI or LOW SPEED when preset pressures are reached.
1-13. HEATING
HI HEAT mode.
When the mode selector switch is set for HI HEAT the six
heating elements, located behind the evaporator coil, are energized. These ele-
ments are protected from overheating by a thermal cutout switch.
Three of the
elements are thermostatically controlled by the temperature control thermostat,
and remaining three are on all of the time.
b.
LO HEAT mode.
When the mode selector switch is set for LO HEAT, only the
three thermostatically controlled elements are used.
1-9/(1-10 blank)
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