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Evaporators
The plate evaporators are made of 316 stainless steel, braze-welded. Unit sizes 040 to size 130 have a
single water side circuit. From unit size 140 upwards, the circuits are double “cross flow” type. The use of
these types of evaporator allows a significant reduction of the refrigerant charge for the unit compared to
traditional shell-in-tube evaporators and increases the efficiency of the refrigerant cycle during part load
operation. The evaporators are factory insulated with flexible close-cell insulation and can be fitted with an
antifreeze heater (optional). Each evaporator is provided with a temperature sensor as antifreeze protection.
Hydraulic circuit (K versions only)
QLAC chillers can be supplied with an optional built in hydraulic kit that includes:
Water tank: various capacities (depending on the size of the unit), factory insulated with flexible close-cell
material and ready for installation of an antifreeze kit (option). The water tank is installed on the supplied
water side (7°C) in order to minimize fluctuations in the water temperature caused by cycling of the
compressors. By installing on the supply side, the supply water temperature can be maintained for some
time after the compressors turn off, a situation that cannot be achieved if the water tank is installed on the
return water side (12°C).
Water pump: centrifugal type, is available in single (K1) or double configuration (K2). In the K2 version, one
pump is running and one pump is in stand-by. The change over can be manual (by a manual switch installed
in the electric box) or automatically controlled by the microprocessor (option). The expansion vessel, safety
valve and manual valves with fittings are sited in the hydraulic circuit.
Electrics enclosure
Access to the electrics enclosure is achieved by switching the mains isolator to "OFF" and removing the
front cover.The electrics conform to electromagnetic compatibility norms CEE 73/23 and 89/336. Moisture
protection is IP55.
All QLAC units have installed, as standard, a compressor sequence relay, which disables compressor
operation if the power supply phase sequence is incorrect (scroll compressors can be damaged if they
operate in reverse). The following components are also installed as standard:
Mains switch, Magnetic-thermal switches (MCB's) for protection of pumps and fans
Compressor fuses Control circuit automatic breakers
Compressor contactors Fan contactors, pump contactors.
The terminal board is supplied with volt free contacts for remote ON-OFF, Heat / Cool change over (heat
pumps only) and general alarms.
Microprocessors
QLAC units are supplied with microprocessor controls as standard. The specific controller used depends
upon the unit size, number of features and use of optional features e.g. electronic expansion valves.The
microprocessor controls the following basic functions:
regulation of the water temperature
antifreeze protection
compressor timing
compressor automatic starting sequence
alarm reset
volt free contact for remote common alarm
alarms and leds.
Any microprocessor can, on request, be connected to a BMS system for remote control and management.
Typically, solutions can be found for MODBUS, LONWORKS, BACNET or TREND protocols.
Control and protection devices
All units are supplied with the following control and protection devices:
Return water temperature sensor, installed on the return water line from the plant (12°C)
Antifreeze protection sensor installed on the outlet water temperature (7°C)
High pressure switch with manual reset
Low pressure switch with automatic reset
High pressure safety valve
Compressor thermal overload protection
Fan thermal overload protection
Flow switch. (std versions supplied loose, K versions factory fitted)