Introduction
15
Chillers
DeltaChill
TM
DeltaChill Technical Manual 9758541 V1.1_06_2020
Refrigerant Leak Detection
A factory calibrated leak detection system shall be fitted as standard. If the unit includes a compressor enclosure, a
refrigerant sensor shall be fitted within this enclosure and will raise an alarm on detection of refrigerant gas. The alarm
state will activate an ATEX certified ventilation fan within the enclosure and the unit will immediately shut down, closing
the EEV and actuating the isolation contactor to disable all non-essential electrical circuits. The unit will remain turned off
(not pumped down) until it is manually reset; the unit can only be reset when the refrigerant level is below the trip setting.
HP / LP Transducers and Switches
HP / LP Transducers and switches are fitted to the unit to protect against high or low pressures.
High pressure switches are manual reset.
Dual Pressure Relief Valve
A 3-way dual shut-off valve that incorporates 2 relief valve assemblies per circuit. The valve allows the maintenance of
individual pressure relief valves without the need for refrigerant evacuation. The pressure relief valve
protects the evaporator.
Head Pressure Control
Electronic head pressure controllers are fitted which modulate the fan speed to maintain a constant condensing
pressure, allowing the system to operate satisfactorily in ambient temperatures as low as -30°C.
Head pressure can be set, monitored and values viewed at the microprocessor display.
Electronic Expansion Valves (EEV)
Electronic expansion valves differ to the normal thermostatic expansion valves in their ability to maintain control of the
suction superheat at reduced head pressures. This can lead to significant energy savings particularly at reduced loading
and low ambient temperatures.
Key
Cooling Cycle @ 22°C ambient with a conventional TEV fitted.
Cooling cycle @ 22°C ambient, demonstrating a typical EEV condensing
temperature taking full advantage of lower ambient air temperatures (below
30°C).
Heat of Rejection
Reduction in
Compressor Input
Power
Enthalpy kJ/kg
Increase in
Cooling Duty
Evaporating
Pressure
Reduced
Condensing
Pressure
Presssure
Bara
Thermostatic Expansion Valve (1)
Electronic Expansion Valve (2)
1
2
3
4
Filter Driers
Maintainable filter driers are fitted with replaceable cores, to protect the system from moisture, acids and solid
contaminants. They help to maintain system efficiency and prevent premature compressor failure.
Using an EEV allows for good refrigeration control whilst operating at part load and lower ambient conditions with a
reduced condensing pressure. By fitting an EEV and adjusting the head pressure control setting an increase in the
system EER (Energy Efficiency Ratio) can typically be seen at lower ambient conditions.
The Mollier diagram shown below helps to illustrate how this increase in efficiency is achieved.