Chillers
This section of the specification details the requirements of materials, workmanship and other accessories in respect of Air Cooled Chiller Units.
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The chiller unit shall consist of galvanised steel cabinet mounted on a frame, the whole of which shall be rust proofed and finished with a scratched-resistant and wear resistant baked on enamel so as to resist marine environment corrosion. Removable panels shall be provided to enable all maintenance and repairs to be carried out without removal of the unit or structural alteration to prevent rattles and looseness after prolonged period of operation.
The inside of the cabinet (where the compressor is located) shall be insulated with 2” thick high density fiberglass or Rockwool. The nuts and bolts shall be treated with anti rust and coat with rust proof paint.
Popular Industrial Chiller Manufacturers
- Trane Air Cooled Chillers
- Carrier Chillers
- Hitachi Chillers
- Mcquay Chillers
- Dunham Bush Chillers
- York Chillers
- Clivet Chillers
- Daikin chiller
Compressors
The air cooled chiller shall be fitted with two or more screw compressors of the semi-hermetic or the accessible hermetic type. In either case, the availability of spare parts shall be assured. The bidders may offer other types of compressors as alternatives.
The compressors shall be driven by electric motors designed for operation on 440 volts, 50 cycle, 3-phase. Compressors motors shall be cooled with suction gas or other approved means.
The compressors and motors shall be fully protected against abnormal operating conditions by high and low pressure switches, thermal relays, overload relays and safety controls and Phase Failure fuses.
The compressors shall be fitted with gauge connections for reading oil, suction and discharge pressures and shall be fitted with a sight glass, crankcase heater, muffler, discharge manifold and internal motor protection.
The compressors shall be mounted on spring vibration isolators.
Warranty of compressor: The air conditioning contractors shall note that the complete compressors unit shall be guaranteed for a period of five (5) years from the date of hand-over. Failure of any part will require complete replacement of the compressor unit at no extra cost to the Purchaser. Rewinding of motor windings will not be acceptable.
Cooling Coils
The air cooled chiller shall contain a bank of copper tube, aluminum fin cooling coils of approved manufacture with marine environment corrosion resistant coating.
Fins shall be bonded to the primary surface by mechanical means or by other approved means. Fins shall form a regular surface and coils with damaged fins will be rejected by the Consulting Engineers.
Condensers
The air cooling condenser shall be of the air cooled cross-finned type with copper tube type to suit the capacity of the unit. Bonding of the fins to the tubes shall be by mechanical means to ensure a positive lasting bond.
The condenser fan shall be the propeller type and be statically and dynamically balanced and shall be mounted on a solid steel shaft running in self-aligning ball bearings, amply sized for quiet operation and long life. The condenser fan shall be driven directly by a resiliently mounted squirrel cage induction motor with adequate horsepower for the duty.
Unit Control Panel
Each refrigeration chiller equipment unit shall be furnished with a complete control centre in an enclosure, factory mounted, piped and wired. The capacity, operating and safety controls sequences shall be designed for completely fail safe, automatic operation. The control sequence shall provide for operation of oil heaters during normal shut down.
Provision shall be made in the control centre for inter-locking of compressor motor starter, chilled water pump. Machine shall also be fitted with no-load center and shall contain the following in a weather proof compartment.
- Capacity control shall be modular, solid state and fully automatic. Manual `control switch shall regulate chilled water temperature and prevent motor overload by control of compressor guide vane positioner. Capacity modulation shall be from 100 percent to 10 percent of full load under normal operating conditions. Chilled water temperature controller control points adjustment and the motor current controller with load limiting selector switch.
- Safety controls shall be electric or electronic fully automatic and shall be fail safe. Machine shall shut down for oil low pressure, chilled water low temperature, refrigerant low pressure, condenser high pressure, lubrication oil high and low temperature and surging operation. Each shut down shall be indicated with light individually. Controls centre should be fitted with remote alarm indicating terminals. Machine shall not restart until manually reset.
- Machine shall be provided with start/stop, remote/local and reset switches.
- Machine shall be fitted with dial pressure gauges for refrigerant evaporator and condenser pressures and oil pressure.
- Terminals strips shall be clearly marked for field wiring connections.
System Control Panel
The system control panel module shall be supplied where two or three chillers are connected in parallel. It shall be designed to optimize the control of the chillers and their associated auxiliaries including pumps and condenser fans.
The system control panel shall incorporate the following facilities / features or equivalent:-
- Chilled Water Temperature Sensor
In HVAC chiller system chilled water temperature sensor shall be the system control panel to co-ordinate the operation of the multiple chillers as a system. The panel shall evaluate the chilled water requirements of the building and bring the chillers on or off the system as required. The load shall be balanced between the chillers. Provision shall be included in the panel for chilled water temperature reset for each chiller to save energy when the cooling load is below the design levels.
- Complete Scheduling Capability
The unit shall incorporate seven day, 24 hours clock plus holiday scheduling. Facilities shall be provided for the operator to schedule the chilled water temperature set point.
Energy Saving Control Strategies
- The system control panel shall control the rate of chiller loading to avoid setting electrical peaks during system start up. If the system leaving chilled water temperature is above the set point, the unit shall bring in the chiller to gradually reduce the leaving chilled water temperature within a time frame specified by the operator.
- Electrical demand shall be limited by a electric demand meter as the electrical demand limit is approached.
- System chilled water reset shall be load based. With temperature based control the chilled water set points are changed as a measured temperature varies (i.e. outdoor ambient air) for load based on the return water temperature.
The following operator interface shall be provided:
Dedicated chiller system control strategies
Preformatted system and individual chiller reports
Remote access
Alarm connection
Assembly
The air cooled heat exchanger shall be fabricated an assembled in the factory with all the foregoing listed major components, all refrigerant piping, all necessary oil piping, wiring between all above listed components, evacuation, full charge of refrigerant and oil.
The machine shall be under coated with Epoxy Resin Primer and finished with Phithalie-acid Resin Enamel.
The painted color shall be to the process chillers manufacturers selection.
The chiller and suction piping shall be factory insulated with self extinguishing foam type insulation.
Vibration Isolation Mounting
The unit shall be supplied with adequate number of level adjusting spring type isolation provided by the manufacturer.
Testing In Factory
The machine shall be tested fully in the factory in the presence of the consulting engineer and shall include the following:
- Setting of all protective controls.
- Operation of unit and necessary adjustments of operating conditions.
Load tests at full and partial loads with power consumption data tabulated.
Refrigerant
The refrigerant offered in industrial refrigeration system shall comply with the intent of Montreal Protocol Agreement for phasing out CFC’s by the year 1995.
The chiller units and accessories offered now shall be suitable for use with the new generation of refrigerants without loss in capacity or efficiency or costly replacement of parts.
To achieve the objectives the selected equipment shall:
- Be charged with refrigerant unaffected by the Montreal Protocol or
- Be suitable for operation with dual refrigerants (i.e. R11, R12, R22 etc. at present and R123, R134 etc. at a later date) in which case.
- The machine shall be selected for optimum operation when charged with refrigerant unaffected by the Montreal protocol and be installed with presently available refrigerant.
- The machine shall provide not less than the specified refrigerant capacity when charged with either refrigerant and operating at the specified water flow rates and temperatures.