Emerson COPELAND ZO18AG, Инструкции по применению

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In order to ensure positive compressor protection, discharge gas temperature protection is required
for any application with Copeland compressors.
The maximum discharge gas temperature is 135 °C for ZO(V)*AG compressors.
Discharge gas temperature protection is the "fall-back" for failure of the system control. It is essential
that proper control of both the evaporating and condensing pressures and the superheat is
maintained and has the ability to cope with all likely conditions and high loads. Reliance on protectors
will cause inadequate system performance and short cycling.
NOTE: The maximum discharge gas temperatures indicated in this chapter are valid for safe
operation within the approved application envelope. The discharge line thermostat has the
function of a compressor protection device; it is not designed to control the operating
envelope. For compressor envelope control, an additional control device or regulation must
be used.
3.6.1 Excessive discharge gas temperatures
A few of the possible consequences of excessive discharge gas temperatures are listed below:
▪
Since the oil circulates in the system with the refrigerant, it is subjected to high discharge gas
temperatures. If the discharge gas temperature becomes too high, the so-called "cooking" effect
will occur (heating of oil under exclusion of air). Carbon deposits can form at points of high
temperature, for example on the valves, oil channels, oil filters, etc. The oil lubricity will be reduced
and a progressive wear process will occur which will prematurely damage the compressor.
▪
The stability of the refrigerant can also be affected, particularly if traces of contaminant are
present.
The problems listed under the first 2 points frequently occur simultaneously, particularly since the
chemical reaction speed approximately doubles with every 10 °C temperature rise. This directly leads
to chemical reactions of the oil with the refrigerant and the compounds extracted from sealants and
insulation material. As a consequence, contaminants of various types, among them acids, will form
inside the system.
3.6.2 Discharge temperature sensor NTC
Variable- and fixed-speed compressors need an external discharge line temperature sensor. The
correct reading of this sensor is fundamental for discharge line temperature control. The sensor must
ensure accuracy and adequate dynamic behaviour.
Mounting recommendations
▪
The temperature sensor should be installed along the straight or bended pipe at a distance of
120 mm from the compressor outlet.
▪
The sensor must be installed in a copper sleeve to improve response time and to reduce setoff.
The copper sleeve must be brazed on the surface of the discharge pipe.
▪
Use thermal compound to improve the heat transfer from the sleeve to the sensor. The thermal
compound must be approved for maximum system operating temperatures.
▪
The discharge pipe including the sensor must be insulated to reduce the impact of ambient
temperature.
▪
Protect the sensor from being moved or removed from its position by transport, vibration or any
other incident.
Figure 18: Sensor installation
NOTE: For complete mounting recommendations please refer to Assembly Instructions.
C30.11 "NTC Mounting Recommendations".
NOTE: When using an Emerson qualified drive, please refer to the drive user manual to see
how to connect it.