Air Cooled Centrifugal Water Chillers | How Does A Chiller Work

This article describes the minimum requirements for factory assembled air cooled centrifugal water chillers including compressor motor, motor starter, lubrication system, evaporator, condenser, controls, and interconnecting piping and wiring.

How Does A Chiller Work? 

An aircooled condenser uses ambient air to cool and condense the hot refrigerant gas back down to a liquid. It can be located inside the chiller or can be remotely located outside, but ultimately it rejects the heat from the chiller to the airResource by ThermalCare.

How Does A Chiller Work? Air Cooled Centrifugal Water Chillers

How Does A Chiller Work? Air Cooled Centrifugal Water Chillers

Air Cooled Centrifugal Water Chillers

Submittals

Product data shall include refrigerant; rated capacities; shipping, installed, and operating weights; certified dimension drawings, piping connections, furnished specialties; and accessories for each model indicated.

Shop Drawings:

a. Wiring diagrams indicating power, signal and control wiring. Wiring diagrams shall differentiate between manufacturer installed and field installed wiring.

b. Access requirements around other work, including working clearances to mechanical controls and electrical equipment.

c. Certification of performance in accordance with ARI 550.

Operation, installation and maintenance data shall be submitted for air-cooled centrifugal water chillers to including operation, installation and maintenance manuals.

Quality Assurance

  1. Electrical components, devices, and accessories shall be listed and labeled as defined in NFPA 70, Article 100, by a testing agency acceptable to authorities having jurisdiction, and marked for intended use.
  2. Chiller design, construction, leak testing, and installation shall comply with ASHRAE 15.
  3. Chillers shall comply with ASME BPVC: Section VIII, for construction and testing evaporator and condenser pressure vessels. Chillers shall be stamped with an ASME label.
  4. Chillers shall comply with UL 1995.
  5. Chillers shall comply with NFPA 70.
  6. Chillers shall be rated in accordance with ARI 550.
  7. Chillers shall be factory tested for the following:

a. Sound power level ratings in accordance with ARI 575

b. Centrifugal water chiller performance ratings in accordance with ARI 550 and ASHRAE

Casing

Exterior casing shall be manufacturer’s standard equipment casing coated with corrosion resistant exterior finish and with removable doors or panels for service and inspection.

Compressors

    • Compressors shall be cast iron casing with high strength, cast aluminum alloy impeller on carbon or forged steel shaft; statically and dynamically balanced compressor assembly; and overspeed tested at 120 percent of design operating spe
    • Compressor capacity control shall be by the use of variable, inlet guide vane assembly for stable operation that is free of surge, cavitation, or vibration throughout throttling range from full load to 20 percent lo
    • Oil pump shall be positive displacement, submersible pump with heater, strainer, and sight glas
    • Chiller shall be come with a full operating charge of non-CFC refrigerant and oil.

Liquid Cooler

    • Cooler shall be shell and tube design with refrigerant totally enclosed in shell and water in tubes. 
    • Shell material shall be carbon steel plate.
    • Tubes shall be seamless, externally finned, individually replaceable tubes; expanded into tube sheets.

a. Material shall be copper, 90/10 copper nickel alloy or titanium as defined by specific project requirements.

b. Internal finish shall be smooth or enhanced.

c.    External finish shall be smooth or enhanced.

    • Water boxes shall be standard, removable, carbon steel, with vent and drain connecti
    • Refrigerant working pressure shall be 2070 kP
    • Water side working pressure shall be 1040 kPa.
    • Insulation shall be factory applied to evaporator, suction lines, and other surfaces where condensation might occur, with flexible elastomeric insulation of the 13 mm thickness minimu
    • Eliminators shall be metal screen mesh to prevent refrigerant carryover into compressor.
    • Pressure relief shall be by frangible carbon rupture disc or single or multiple, reseating type, spring-loaded relief valves.

Condenser

    • Condenser construction shall be shell and tube design with water enclosed in tubes and refrigerant enclosed in shel
    • Shell material shall be carbon steel pl
    • Condenser tubes shall be seamless, externally finned, individually replaceable tubes; expanded into tube sheets.
    • Material shall be copper, 90/10 copper nickel alloy or titanium as defined by specific project requirements.
    • Internal finish shall be smooth or enhanc c.  External finish shall be smooth or enhanced.
    • Water boxes shall be standard, removable, carbon steel, with vent and drain connecti
    • Refrigerant working pressure shall be 2070 kP
    • Water side working pressure shall be 1040 kPa.
    • Pressure relief shall be by single or multiple, reseating type, spring-loaded relief valves.

Purge Unit

Purge unit shall pump out unit, air, water, or refrigerant cooled, with automatic controls to remove and separate non-condensables, and return refrigerant to chiller.

Control Panel

Control panel shall be manufacturer’s standard microprocessor based chiller controls; unit or remote mounted, and factory wired with a single-point power connection and separate control circuit.

Status display shall include the following conditions:

    1. Date and time
    2. Operating or alarm status
    3. Operating hours
    4. Entering chilled water temperature
    5. Leaving chilled water temperature
    6. Evaporator refrigerant temperature
    7. Condenser refrigerant temperature
    8. Oil supply temperature
    9. Oil sump temperature
    10. Percent motor amperage

Control functions shall include the following:

a. Manual or automatic startup and shutdown time schedule

b. Leaving and entering chilled water temperature, control set points, and motor load limit

The following conditions shall shut down chiller and require manual reset:

    1. a. Evaporator low pressure
    2. b. Evaporator low temperature
    3. c. Low oil flow
    4. d. Low oil pressure
    5. e. High oil temperature
    6. f. High bearing temperature
    7. g. High condenser pressure
    8. h. High compressor discharge temperature
    9. i. No or low chilled water flow
    10. j. Sensor or detection circuit fault
    11. k. Processor communications loss
    12. l. Starter fault
    13. m. Extended compressor surge

Motor Starter

Power controls shall be combination controller and disconnect with star delta (wye delta), solid-state or across the line starting.

Motor protection shall include:

    1. a. High winding temperature
    2. b. Overvoltage protection
    3. c. Undervoltage protection
    4. d. Electrical distribution faults, including phase loss, phase unbalance, and phase reversal e.    Current overload protection

Vibration Control

Vibration control shall be by direct isolation and either rubber mounts with minimum deflection of 6.4 mm or restrained spring isolators with minimum deflection of 19 mm isolators.

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