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The EWFD air cooled screw chillers have been designed and optimized to operate with HFC 134a refrigerant. The components such as compressors and shell and tube heat exchangers have also been designed and optimized for this refrigerant.

The models EWFD 300.2 to 960.2 can be equipped, as optional, with total heat recovery system (composed mainly of additional condensers, liquid receivers and 4-way valves) allowing to recover all the condensing heat for the production of domestic hot water.

These chillers are available in 2 ranges : Standard (EWFD STD) and High Efficiency (EWFD AEE).

The EWFD STD range is composed of 23 sizes, 300.2 to 1650.4, covering a nominal cooling capacity range from 293 to 1646 kW.

The models EWFD STD 300.2 to 960.2 (15 sizes) consist of 2 independent refrigerant circuits with one screw compressor on each circuit and one new double circuit pure counter flow shell and tube type heat exchanger. These models are based on 3 frame sizes : 4, 6 and 8 meter long frames.

The models EWFD STD 1030.4 to 1650.4 (8 sizes) are composed of 4 independent refrigerant circuits with one screw compressor on each circuit and two new double circuit pure counter flow shell and tube type heat exchangers. Each unit is supplied with two independent electrical boards located on each end of the unit. These units are based on 8, 10 and 12 meter long frames.

The EWFD AEE range is composed of 24 sizes, 300.2 to 1650.4, covering a nominal cooling capacity range from 304 to 1686 kW. The models EWFD AEE 300.2 to 960.2 (15 sizes) consist of 2 independent refrigerant circuits with one screw compressor on each circuit and one new double circuit pure counter flow shell and tube type heat exchanger. These models are based on 3 frame sizes : 4, 6 and 8 meter long frames. The models EWFD AEE 1060.4 to 1650.4 (9 sizes) are composed of 4 independent refrigerant circuits with one screw compressor on each circuit and two new double circuit pure counter flow shell and tube type heat exchangers. Each unit is supplied with two independent electrical boards located on each end of the unit. These units are based on 12 meter long frame.

Each of the two ranges (EWFD STD and EWFD AEE) is available in 3 acoustic versions: Base Low Noise (STD), Low Noise (SI) and Extra Low Noise (SS).
- STD version : This version is equipped with Delta connected fans. Each fan is located in an externally mounted nozzle profile housing generating low sound level. The compressors are housed in a protective box.
- SI version : The units of this version have the same condenser coils and fans as the STD units, but the fans are Star connected. Each fan is located in an externally mounted nozzle profile housing. In addition, the units are equipped with an acoustically insulated box mounted on compressors.
-SS version : The SS units have the same equipment as the SI ones (same condenser coils and fans). The fans are Star connected for all sizes. In addition, the units are equipped with fan speed controller, acoustically insulated compressors box, and flexible pipes as well as mufflers mounted on compressor discharge lines.
The EWFD AEE high efficiency range differs from the EWFD STD standard one by the greater surface area condenser coils and by the greater number of fans.

Frame and cabinet
The unit frame and cabinet are made of heavy gauge galvanized steel, fastened with non-corrosive screws and bolts.
The galvanized steel parts are coated with polyester resin based white colour (RAL 9001) painting.

Semi-hermetic screw compressors
The compressors installed in the EWFD units are of semi-hermetic twin screw type integrating step type cooling capacity control system. All compressors are fitted with an electronic control system ensuring the following functions :

- protection against high temperature and excessive load ;
- correct direction of rotation ;
- phase monitoring.

The main features of cooling capacity control of each compressor are stated below :
- compressor capacity reduction by means of solenoid valves ;
- capacity reduction steps relating to each compressor : 25% (at start-up and pump down), 50%, 75% and 100% ;
- 6 capacity steps are then provided on 2 refrigerant circuit units : 25%, 50%, 63%, 75%, 87% and 100% and 9 steps on 4 refrigerant circuit units.

Furthermore, the screw compressors are provided with control devices to make the EWFD units more reliable :
- electric motor temperature sensor ;
- discharge temperature sensor.
The compressors are supplied with a Part-Winding and/or Star-Delta starting system (refer to section Compressor electrical data).

Refrigerant circuits
Each EWFD unit has 2 or 4 independent refrigerant circuits according to the models.
Each refrigerant circuit is composed of components as shown in the section Refrigerant flow diagram.

Evaporators
New generation of pure counter flow shell and tube type evaporators optimized for operation with HFC 134a refrigerant. The twin units are fitted with two independent exchangers that can be connected by inlet and outlet connecting manifolds supplied as optional extra. They are insulated with a 19 mm thick closed cell foam material and are fitted
with an electric cable resistance on the external surface to prevent the unit from freezing at a low temperature (down to -18 °C), when the unit is off.

Total heat recovery condensers (optional)
Shell and tube type condensers fitted on the gas discharge lines, in parallel with the standard cooling circuits. Each unit is equipped with two heat recovery condensers, one on each circuit. Thanks to the 4-way valves used in the heat recovery system, the mode switching from cooling only mode to heat recovery mode is totally synchronized.
With such system, there is no any refrigerant stagnation in the condenser coils where all the fans are off, because the compressors suck all the refrigerant from the coils. Thus, influence of wind or air temperature is avoided during heat recovery operation.

Condenser coils
The condenser coils are consisting of seamless 1/2 copper tubes, arranged in staggered rows, mechanically expanded into corrugated aluminium fins. The coil circuiting has been specially designed to increase the performance of the refrigerant.

Condenser coil fans
The condenser fans are of direct drive axial type and are composed of wing contour aluminium blades. All fans have diameter of 800 mm. Each of them is fitted with a painted steel protective guard.
Each fan is equipped with a nozzle profile housing which generates low noise level during the operation of the unit.

Fan controls
The standard units operate with an external air temperature down to -5 °C thanks to the use of a fan step controller which consists in deactivating a certain number of fans for each step.
A stepless fan speed controller can be supplied as optional in order to allow the units to operate with an external air temperature down to -18 °C.
The minimum external operating temperature on SS units is -18 °C, thanks to the stepless fan speed controller supplied as standard.

Electrical board
Electrical board is a metal box of IP54 weather protection, arranged inside the unit and protected by a horizontally pivoted external panel.
On the twin units, an auxiliary electrical board (IP54) is located at the opposite end of the unit. In this case, 2-point power supply connections will be supplied. Single point power supply connections can be provided as optional.

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