Evaporators, Hydraulic circuit K versions only

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)

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