D-EOMCP00104-14_01EN
Operating Manual
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EWYD_BZ
recovery circuit operation, the related compressor will trip and the alarm reset will not be allowed up to the flow is recovered
(otherwise recover heat exchanger freeze will occur).
5.20.2
Recovery control
When heat recovery is activated the control will activate or deactivate recovery circuits with a step logic. In particular a
next heat recovery stage is activated (a new heat recovery circuit is inserted) if the heat recovery leaving water
temperature remains below the setpoint by an amount greater than an adjustable regulation band for a timer greater than
an adjustable value (heat recovery interstage). When a recovery stage is requested, the relative compressor is completely
downloaded and then the recovery valve is energized. After recovery valve switches the compressor load is inhibited until
the saturated condensing temperature is lower than an adjustable threshold (default is 30.0°C).
At the same manner a heat recovery stage is deactivated (a heat recovery circuit is removed) if the heat recovery leaving
water temperature remains above the setpoint by an amount greater than an adjustable dead regulation band for a timer
greater than the previous defined value. An high temperature setpoint is active in the recovery loop; it will disable all
recovery circuits at the same time if the heat recovery water temperature rises above an adjustable threshold (def ault
50.0°C). A three-way valve is used to increase recovery water temperature at startup; a proportional control is used to
establish valve position; at low temperature the valve will recirculate recovery water, while at temperature increasing the
valve will bypass a portion of the flow.
5.20.3
Compressor limiting
Two levels of limits are included in the control:
•
Load inhibit.
The load is not allowed; another compressor may start or may be loaded.
•
Forced unload.
The compressor is unloaded; another compressor may start or may be loaded
The parameters that may limit compressors are :
•
Suction pressure
The compressor load is inhibited if the suction pressure is lower than a “stage -hold” setpoint
The
compressor is unloaded if the suction pressure is lower than a “stage-down” setpoint
•
Discharge pressure
The compressor load is inhibited if the discharge pressure is higher than a “stage-hold” setpoint
The compressor is unloaded if the discharge pressure i
s higher than a “stage-down” setpoint
•
Evaporator outlet temperature
The compressor is unloaded if the evaporator outlet temperature is lower than a “stage -down” setpoint
•
Discharge Superheat
The compressor load is inhibited if, the discharge superheat is below an adjustable threshold (default 1.0°C)
for an adjustable time (default 30s) from the compressor starts at the end of prepurge procedure.