Hot Gas By-Pass Valve; Refrigerant Pressure Switches Lps - Hps - Pv; Safety Thermo Switch Ts - pilotair ACT 3T User’s Maintenance & Spare Parts Manual

7.9 Hot Gas By-pass Valve

This valve injects part of the hot gas (taken from the discharge side of the compressor) in the pipe between the
evaporator and the suction side of the compressor, keeping the evaporation temperature/pressure constant at
approx. +2 °C. This injection prevents the formation of ice inside the dryer evaporator at every load condition.
ADJUSTMENT
The hot gas by-pass valve is adjusted during the manufacturing testing
phase. As a rule no adjustment is required; anyway if it is necessary the
operation must be carried out by an experienced refrigerating engineer.
WARNING
the use of ¼" Schrader service valves must be justified by a real
malfunction of the refrigerating system. Each time a pressure gauge is
connected, a part of refrigerant is exhausted.
Without compressed air flow through the dryer, rotate the adjusting screw
(position A on the drawing) until the following value is reached:
Hot gas setting :
7.10 Refrigerant Pressure Switches LPS – HPS – PV
As operation safety and protection of the dryer a series of pressure switches are installed in the gas circuit.
LPS: Low-pressure protection device on the suction side of the compressor, trips if the pressure drops below
the pre-set value. The values are automatically reset when the nominal conditions are restored.
Calibrated Pressure :
HPS: This high-pressure controller device, located on the discharge side on the compressor, is activated when
the pressure exceeds the pre-set value. It features a manual-resetting button mounted on the controller
itself.
Calibrated Pressure :
PV: Fan control pressure switch located at the discharge side of compressor. It keeps the condensing
temperature/pressure constant within preset limits
Calibrated Pressure :

7.11 Safety Thermo Switch TS

23 | P a g e
Technical Description
R134.a pressure 2.0 barg (+0.1 / -0 bar)
R407C pressure 4.5 barg (+0.1 / -0 bar)
R 134.a Stop 0.7 barg - Restart 1.7 barg
R 407 C Stop 1.7 barg - Restart 2.7 barg
R 134.a Stop 20 barg - Manual reset (P<14 bar)
R 407 C Stop 30 barg - Manual reset (P<23 bar)
Start 11 barg (+0.5 / -0 bar) – Stop 8 barg (+0 / -0.5 bar) R
R 134.a
Start 18 barg (+0.5 / -0 bar) – Stop 14 barg (+0 / -0.5 bar)
407 C
To protect the operating safety and the integrity of the dryer, a thermo switch (TS)
is installed on the refrigerant gas circuit. The thermo switch sensor, in case of
unusual discharge temperatures, stops the refrigerating compressor before it is
permanently damaged.
Manually reset the thermo switch only after the nominal operating conditions have
been restored. Unscrew the relative cap (see pos.1 in the figure) and press the
reset button (see pos.2 in the figure).
TS setting: Temperature 113 °C (+0 / -6 °K)
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