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2.4.2 Application limits
CAUTION
Inadequate lubrication! Compressor breakdown! The superheat at the
compressor suction inlet must always be sufficient to ensure that no refrigerant
droplets enter the compressor. For a typical evaporator-expansion valve
configuration a minimum stable superheat of at least 10 K is required.
For application envelopes and technical data, please see Select software available at
www.climate.emerson.com/en-gb.
2.4.3 PED category and maximum allowable pressure PS
The Pressure Equipment Directive PED 2014/68/EU does not apply to 2D*, 3D* and 8D* semi-
hermetic compressors.
The pressure PS is the maximum allowable pressure at the low- and high-pressure sides of the
compressor. The maximum pressure value PS for the individual compressor type is printed on the
nameplate of the compressor. Safety is established in compliance with the relevant standards
applicable to the given product. Also refer to section 3.2.6 "Maximum allowable pressures".
Compressor
High-pressure side
2D*, 3D* & 8D*
Table 3: Maximum allowable pressures
2.5
Design features
2.5.1 Compressor construction
The semi-hermetic compressors covered in these guidelines are suction-gas cooled compressor
models 2D*, 3D* and 8D* with 2, 3 and 8 cylinders respectively and a displacement between
16.8 and 181 m³/hr. They are fitted with Discus™ valve plates.
Each cylinder head has a plugged 1/8" - 27 NPTF tapped hole for connecting a high-pressure switch.
The high-pressure switches must be calibrated and tested before putting the compressor into service.
They must stop the compressor if the allowable pressure is exceeded.
The complete cylinder head is under discharge pressure.
2.5.2 Compressor cooling
With suction-gas cooled compressors, the motor is cooled by the incoming refrigerant, which enters
the compressor and is then passed over the motor area. An additional fan may be required depending
upon the operating conditions – see Select software at www.climate.emerson.com/en-gb.
2.5.3 Liquid injection / Demand cooling
WARNING
Ignition source in a potentially flammable atmosphere! Fire hazard! The
solenoid valve of the liquid injection is not an ignition source during normal
operation in an A2L-refrigerant system but could become one if not installed
properly. Never operate the solenoid coil when not positioned on the solenoid
valve. Secure the installation with a screw.
Liquid injection may be required for low-temperature applications in order to keep the compressor
within safe discharge temperature limits.
Additional liquid cooling can be applied in the low-temperature model versions of 2D* and 3D*
compressors. With this solution, an additional discharge temperature sensor, a separate Demand
Cooling driver and a liquid injection valve kit work together.
For more information also see Section 4.6 "Demand Cooling™".
NOTE: For corresponding application envelopes, please see Select software available at
www.climate.emerson.com/en-gb.
AGL_HA_ST_Discus_A2L_A1_EN_Rev00
PS
Low-pressure side
32.5 bar(g)
PS
22.5 bar(g)
5
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