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Air and Water cooled inverter chillers and heat pump
EWAD TZ - EWAD TZ B - EWWD VZ
Air and Water cooled inverter chillers
and heat pump
D-EOMZC00105-17EN
Operation Manual
9/84
If the circuit operates with a suction pressure lower than an adjustable limit for a certain time the circuit safety
logic will shut down the circuit and generate an alarm. The alarm requires a manual action on the Unit Controller
to be reset. Reset will take effect only if the suction pressure is no longer lower that the safety limit.
High Pressure Protection
If the discharge pressure becomes too high and exceeds a limit which is linked with the operational envelop
of the compressor the circuit safety logic will try to prevent the alarm or, if the corrective actions have no effect,
it will shut down the circuit before the Mechanical High Pressure switch will open. This alarm required a manual
action on the Unit Controller to be reset.
Mechanical High Pressure Switch
Each circuit is equipped with at least one high pressure switch which tries to prevent the relief safety valve to
open. When the discharge pressure becomes too high the Mechanical High Pressure switch will open and
immediately stop the compressor cutting the power supply to the auxiliary relay. The alarm can be cleared as
soon as the discharge pressure becomes normal again. The alarm must be reset on the switch itself and on
the Unit Controller. The triggering pressure value cannot be changed.
Relief Safety Valve
If the pressure becomes too high in the refrigerant circuit, the relief valve will open to limit the maximum
pressure. If this happens switch off immediately the machine and contact your local service organization.
Inverter fault
Each compressor can be equipped with its own inverter (integrated or external). The inverter can automatically
monitor its status and inform the Unit Controller in case of faults or pre-alarm conditions. If this happen the
Unit Controller will limit the compressor operation or eventually switch off the circuit in alarm. A manual action
on the controller will be needed in order to clear the alarm.
1.4 Available sensors
1.4.1
Pressure transducers
Two types of electronic sensors are used to measure suction, discharge and oil pressure on each circuit. The
range of each sensor is clearly indicated on the sensor casing. Discharge and oil pressures are monitored
using a sensor of the same range.
1.4.2
Temperature sensors
The evaporator water sensors are installed in the entering and leaving side. An outdoor temperature sensor is
mounted inside the chiller. Additionally each circuit installs a suction and discharge temperature sensors to
monitor and control the superheated refrigerant temperatures.
On refrigerant-cooled inverters additional sensors immersed into the cooling plate measure the temperature
of the drives.
1.4.3
Thermistors
Each compressor is equipped with PTC thermistors which are immersed into motor windings for motor
protection. Thermistors trip to a high value in case the motor temperature reaches a hazardous temperature.
1.4.4
Leak detectors
As an option the unit can be equipped with leak detectors to sense the air in the compressor cabin and being
able to identify a refrigerant leakage in that volume.