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–EIMWC00803-21_01EN - 15/57
4
MECHANICAL INSTALLATION
4.1
Safety
The machine must be firmly secured to the ground.
It is essential to observe the following instructions:
- The machine must be raised only by the lifting points. Only these points can support the whole weight of the unit.
- Do not allow unauthorised and/or unqualified personnel to access the machine.
- It is forbidden to access the electrical components without having opened the machine
’s general disconnecting switch
and switched off the power supply.
- It is forbidden to access the electrical components without using an insulating platform. Do not access the electrical
components if water and/or moisture are present.
- All operations on the refrigerant circuit and on components under pressure must be carried out by qualified personne l
only.
- Replacement of a compressor or addition of lubricating oil must be carried out by qualified personnel only - Sharp edges
can cause wounds. Avoid direct contact.
- Avoid introducing solid bodies into the water pipes while the machine is connected to the system.
- A mechanical filter must be installed on the water pipe connected to the heat exchanger inlet.
- The machine is supplied with safety valves, that are installed on both the high and the low pressure sides of the refrigerant
circuit.
If the unit mounts suction and discharge valves they need to be secured in open position when the
unit is installed, by means of a lead seal or equivalent. This to avoid they are put in closed position.
The use of this valve is intended for compressor maintenance.
4.2
Positioning and assembly
The unit must be mounted on a level concrete or steel base and must be located to provide service clearance at one end
of the unit for possible removal of evaporator tubes and/or condenser tubes. Evaporator and condenser tubes are rolled
into the tube sheets to permit replacement if necessary. The length of the vessel should be allowed at one end. Doors or
removable wall sections can be utilized for tube clearance.
Minimum clearance at all other points, including the top, is 3 feet (1 meter).
The shipped-loose neoprene vibration pads should be located under the corners of the unit (unless the job specifications
state otherwise). They are installed to be flush with the sides and outside edge of the feet. Most DWSC units have six
mounting feet although only the outer four are required. Six pads are shipped and the installer can place pads under the
middle feet if desired.
Make sure that the floor or structural support is adequate to support the full operating weight of the complete unit.
It is not necessary to bolt the unit to the mounting slab or framework; but should this be desirable, 1 1/8
” (28.5 mm)
mounting holes are provided in the unit support at the four corners.
4.3
System water volume
All chilled water systems need adequate time to recognize a load change, respond to that load change and stabilize,
without undesirable short cycling of the compressors or loss of control. In air conditioning systems, the potential for short
cycling usually exists when the building load falls below the minimum chiller plant capacity or on close-coupled systems
with very small water volumes.
Some of the things the designer should consider when looking at water volume are the minimum cooling load, the minimum
chiller plant capacity during the low load period and the desired cycle time for the compressors.
Assuming that there are no sudden load changes and that the chiller plant has reasonable turndown, a rule of thumb of
“gallons of water volume equal to two to three times the chilled water gpm flow rate” is often used.
A properly designed storage tank should be added if the system components do not provide sufficient water volume.
4.4
Condensation control with evaporative cooling tower
The minimum condenser inlet water temperature should not be less than 20 °C at full water tower flow rate.
If the water temperature must be lower, even the water flow must be reduced proportionately.
To modulate the water flow to the condenser, install a three -way by-pass valve. The figure shows how the three-way valve
is applied to cool the condenser. The three-way valve can be activated by a pressure actuator which guarantees proper
condensing pressure in the case where the water temperature entering the condenser is less than 20 °C.
A three-way servo-controlled valve or inverter driven circulation pump could be used instead of a valve with pressure
actuator. Both of these devices could be controlled by a 0 -10 Vdc analogue signal emitted by the machine electronic
controller according to the condenser inlet water temperature.