C6.1.11/0718-0619/E
27
Figure 34: Sensoring in subcritical mode
2.10.3.2 Transcritical operation
For temperatures typically above 27°C (
AIC7 > GC1
), the system operates in transcritical mode.
▪
According to the gas cooler outlet temperature detected by the
AIC7
probe, the high-pressure
valve modulates to maintain a pressure that maximizes the COP (Coefficient of Performance).
▪
The fan speed setpoint is +5°C with a proportional band of +5K.
2.10.3.3 Transcritical operation with flashgas bypass
In transcritical operation mode in CO
2
systems, the liquid receiver becomes a flashtank, in which the
liquid phase is separated from the gas phase. In high ambient conditions, the amount of gas will
increase due to the thermodynamic properties of CO
2
. Flashgas ratios of 50% or more are not
unusual. Typically, the flashgas is removed to the compressor suction side to keep the pressures in
the flashtank at acceptable levels.
Bypassing flashgas will reduce the mass flow coming from the cold rooms/cabinets. This necessary
process will however reduce the total system efficiency. The flashgas-bypass valve limits the
maximum pressure in the flashtank to 43 bar (adjustable with parameter
GC20
according to
application and piping design).
▪
The fan speed setpoint is +5°C with a proportional band of +5K.
2.10.4 Alarms
In the event of an alarm, the alarm symbol will be flashing on the main display.
Figure 35: iPro Alarm flashing symbol
Summary of Contents for Copeland EazyCool OME-4MTL-09X
Page 1: ...Copeland Eazycool CO2 Refrigeration Units Application Guidelines ...
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