Glossary

Absorber - In an absorption cycle, the vessel in which a lithium bromide solution absorbs low-pressure refrigerant eater vapor produced in the evaporator.

Absorption Cycle - Absorption chillers differ from mechanical vapor compression chillers in that they utilize a thermal or chemical process to produce the refrigeration effect necessary to provide chilled water. There is no mechanical compression of the refrigerant taking place within the machine as occurs within more traditional vapor compression type chillers. Most commercial absorption chillers utilize lithium bromide (a salt) and water as the fluid pair; lithium bromide being the absorbent, water being the refrigerant. In order to produce the refrigeration effect necessary to make, for example, 44F chilled water, the shellside of the machine must be maintained in a deep vacuum to allow the refrigerant (water) to boil at approximately 40F. The lithium bromide solution absorbs the vaporized refrigerant, diluting it before it is pumped to the generator section of the machine where heat is added to reconcentrate the dilute solution. The water vapor boiled off in the generator is then condensed, returning to the evaporator as liquid. The reconcentrated lithium bromide returns to the absorber section as strong solution to begin the cycle again.

Accumeter - The metering (flow control) device inside an Evergreen Centrifugal Chiller. It's unique design always feeds the cooler with liquid refrigerant, which has a much greater cooling capability than a gaseous refrigerant. Carrier patented design.

AEL - Allowable Exposure Limit

AFBMA - Anti-Friction Bearing Manufacturers Association.

ANSI - American National Standards Institute

ARI - Air Conditioning and Refrigeration Institute

ARI 550 - Air Conditioning and Refrigeration Institute Standard 550-1992: Standard for Centrifugal and rotary screw water-chilling packages. The purpose of the standard is to establish , for centrifugal chillers and rotary screw water-chilling packages: definitions and nomenclature; a description of what constitutes such a package; published rating conditions; standard requirements for testing and a basis for published ratings; and proper refrigerant designations in systems.

ASHRAE - American Society of Heating Refrigeration and Air Conditioning Engineers

ASME Construction - Strict design, manufacture, and testing standards set forth by the American Society of Mechanical Engineers. It involves independent inspection of every Evergreen chiller built.

Bolt-Together Construction - Allows a chiller to be taken apart into modules and brought into buildings through standard doorways.

Burner - In an absorption cycle, the lithium bromide solution is reconcentrated for the next cycle in low- and high-stage generators through boiling off of water. The burner supplies the heat necessary for this process.

Capacity - The measure of the amount of heat removed by a chiller, measured in tons of refrigeration (English units) or kilowatts of refrigeration (SI Metric units).

CCN - Carrier Comfort Network. A complete system for the management of HVAC building operations. CCN includes operator interfaces (ComfortWORKS and Building Supervisor), product controls (Product Integrated Controls [PICs]), system managers (Chillervisor, Digital Air Volume, and Flotronic System Manager), and controls for other HVAC and non-HVAC building components (Comfort Controllers).

Centrifugal Compressor - A type of compressor used in vapor compression refrigeration cycles where a rotating impeller is the device which compresses the refrigerant vapor. The vapor is drawn into the impeller axially, and is discharged radially after energy is added to the vapor within the impeller.

Chlorine-Free Refrigerant - A refrigerant containing no chlorine. The presence of chlorine in refrigerant compounds contributes to the depletion of ozone in the atmosphere.

Compressor - In a vapor compression cycle, the device that increases the pressure and temperature of refrigerant vapor. It continuously draws low pressure refrigerant vapor from the cooler, adds energy to increase the refrigerant pressure and temperature, and discharges the high pressure vapor to the condenser.

Condenser - A device for removing heat from a refrigeration system. This heat exchanger typically consists of a hollow steel shell with copper tubes running through it. Relatively cool water is pumped through the tubes, which is cold enough to condense the refrigerant vapor inside the shell, changing its state to a liquid.

Cooler - A device for absorbing unwanted heat into a refrigeration system. This heat exchanger typically consists of a hollow steel shell with copper tubes running through it. The fluid being chilled (relatively warm water) is pumped through the tubes. Heat is transferred from the chilled fluid to the refrigerant liquid inside the shell, boiling it and changing its state to a vapor.

COP - Coefficient of performance. This is a measure of the energy efficiency of a chiller.

CSA - Canadian Standards Association

Demand Limiting - Limits the power draw of the chiller during peak loading conditions.

Diffuser - Part of a centrifugal compressor that transforms the high velocity, low pressure gas exiting the impeller into higher pressure, low velocity gas discharged into the condenser.

Dynaglide Transmission - Transmission design on the Carrier Evergreen Chillers. It features AGMA class 11 gears, tilting pad thrust bearing, and single piece design, which assures alignment, even after disassembly. Carrier patented design.

Economizer - In a chiller with a two-stage centrifugal compressor, the discharge from the first stage impeller and the inlet to the second stage impeller are at a pressure level approximately half way between the cooler pressure and condenser pressure. With this arrangement, an economizer may be used. This is a shell within which refrigerant liquid from the condenser drops down to the interstage pressure, flashing off some of the refrigerant which is drawn directly into the second stage impeller. This reduces the amount of refrigerant which has to be compressed by the first stage impeller, improving the refrigeration cycle efficiency. A similar arrangement may be used with a screw compressor when the compressor is equipped with an intermediate inlet port.

Evaporator - See Cooler.

FLASC - Flash SubCooler. This is a section of some Carrier condensers in which the pressure of condensed refrigerant liquid is reduced, which causes some of the liquid to flash into vapor, cooling the remaining liquid. The vapor is then re-condensed at the lower pressure, which improves the energy efficiency of the chiller.

Generator - In an absorption cycle, the vessel in which the lithium bromide solution is reconcentrated by boiling off the previously absorbed water.

HCFC-22 -

HFC-134a - A positive pressure, chlorine-free refrigerant having zero ozone depletion potential. HFC-134a is the refrigerant of choice for automotive and appliance applications, which will assure a plentiful supply at reasonable prices.

Heat Exchangers - The parts of a chiller which exchange heat between two physically separated fluids. In a chiller, the heat exchangers are the cooler and the condenser, which exchange heat between the refrigerant and water or brine. Typically the heat exchangers used in chillers are of shell-and-tube design, where the water or brine flows through a number of tubes inside a containment shell, and the refrigerant is either boiled or condensed on the outside of the tubes.

Hermetic Motor - A motor which is sealed within the refrigerant atmosphere inside a chiller, and which is therefore isolated from the atmosphere outside the chiller. A hermetic motor is efficiently cooled by liquid refrigerant sprayed directly on the motor windings, and is smaller and lighter than a comparable air-cooled motor. A compressor driven by a hermetic motor has the advantage that the compressor shaft does not have to pass through a seal between the outside atmosphere and the refrigerant atmosphere inside the chiller.

High-Stage Generator - In an absorption cycle, the vessel that performs the first stage of reconcentration of the lithium bromide solution by boiling off the water contained in the solution. The hot water vapor boiled off within the high-stage generator is used as the heat source for the low-stage generator.

Hot Gas Bypass - A system where some high pressure refrigerant vapor at compressor discharge conditions is returned directly to the cooler pressure, without being condensed. This system is sometimes used to permit a chiller to operate at a lower capacity than would otherwise be possible. The efficiency at the low load suffers because the bypassed gas, which does no useful work, still has to be compressed by the compressor.

Impeller - Rotating part of a centrifugal compressor which increases the pressure of refrigerant vapor from the cooler pressure to the condenser pressure.

Inlet Guide Vanes - Movable blades at the inlet of a centrifugal compressor which are used to control the capacity of the compressor. The guide vanes also provide rotation to the refrigerant vapor entering the compressor, which improves the efficiency of the compressor.

ISO 900 Series -

Isolation Valves - Valves used for the transfer and isolation of refrigerant charge in the cooler or condenser, allowing refrigerant to be stored inside a chiller during servicing.

Kingsbury-Type Thrust Bearing - Self-leveling type of thrust bearing which equalizes bearing loading over the entire circumference of the bearing, and providing an optimum oil film shape. This design reduces bearing wear and provides high reliability and long bearing life.

LCD - Liquid Crystal Display

Lead/Lag - A control system process that automatically starts and stops a lag or second chiller in a two chiller water system.

LID - Mounted in the control center, this allows the operator to interface with the PSIO or other CCN devices.

Lift - In a vapor compression cycle, the lift on the compressor is the difference between the high side (condenser) conditions and the low side (cooler) conditions, measured as either a temperature or pressure difference.

Low-Stage Generator - In an absorption cycle, the vessel that performs the second stage of reconcentration of the lithium bromide solution. The heat source for the low-stage generator is the steam created in the high-stage generator.

Lubrication System - System in a chiller, consisting of an oil pump, oil cooler, and associated tubing and oil passages, which provides the oil needed to lubricate the compressor bearings.

Marine Waterbox - A type of waterbox in which the nozzles are oriented at right angles to the axis of the heat exchanger shell, and are connected into the sides of the waterboxes, rather than into the covers. This allows the covers to be removed, for inspection or cleaning of the heat exchanger tubes, without disturbing the external pipes.

NIH - Nozzle in head.

NPFA - National Fire Protection Association

Nozzle-In-Head Waterbox - A type of waterbox in which the nozzles enter through one or both of the waterbox covers, with the nozzles oriented parallel to the axis of the heat exchanger shells.

Oil Separator - In a chiller utilizing a screw compressor, an oil separator is often used to remove lubricating oil from the refrigerant vapor at the discharge of the compressor, in order to keep the oil from collecting in the heat exchangers.

Open-Drive Motor - A motor which is located outside the refrigerant containment of a chiller. An open-drive motor requires that the rotating compressor shaft pass through a seal between the outside atmosphere and the refrigerant atmosphere inside the chiller.

Passes - In a shell-and-tube heat exchanger, the number of passes is the number of times the fluid flowing inside the tubes flows the length of the heat exchanger. For example, a two-pass cooler has the cooled fluid inside the tubes flowing from the inlet end of the cooler to the opposite end, and then back to the inlet end, where the fluid exits the cooler.

PIC - Product Integrated Control. PICs are used in conjunction with the Carrier Comfort Network to control and monitor the operation of Carrier chillers.

Positive Pressure Design - A chiller design using a refrigerant which operates above atmospheric pressure in all parts of the system. These chillers are typically smaller than negative pressure design chillers at similar capacities, and air and water vapor are kept out of the system by the positive pressure difference.

Power Panel - Houses all 230 or 115 control voltage components.

PSIO - Processor Sensor Input/Output module

Pumpdown Unit - System which transfers refrigerant from a chiller to a storage tank, or into an isolated section of a chiller, for service. The pumpdown unit is also capable of evacuating a chiller prior to re-introducing the refrigerant, for minimum contamination of the refrigerant by air or water vapor.

Purge Device - A device which removes air and water vapor from the refrigerant inside a chiller. A purge is a necessity in negative pressure designs, but is not necessary in positive pressure designs where air and water vapor are kept out of the system by the internal pressure.

Refrigerant - The fluid which removes heat from the fluid being chilled and rejects the heat into the cooling fluid. In a vapor compression cycle, the refrigerant undergoes two changes of state: refrigerant liquid is boiled into low pressure vapor in the cooler as it removes heat from the chilled fluid; high pressure refrigerant vapor is condensed to a liquid in the condenser as it gives up heat to the cooling fluid.

Screw Compressor - A type of compressor used in vapor compression refrigeration cycles where two intermeshing helical rotors create pockets of continuously decreasing volume, in which the refrigerant vapor is compressed and its pressure is increased from cooler pressure to condenser pressure.

Single Stage Centrifugal Compressor - Type of centrifugal compressor having one impeller.

Slide Valve - In screw compressors, this is the capacity control mechanism.

SMM - Starter Management Module. This implements PSIO commands for starter functions.

Solenoid valve - In screw compressors, this is the mechanism that controls the movement of the slide valve through signals from the PSIO.

Solid State Starter - Provides smooth, stepless acceleration of a chiller's motor from stop to full speed. The "soft start" reduces the mechanical stress on the compressor.

Storage Tank - A steel shell in which the refrigerant charge for a chiller may be temporarily stored while the chiller is serviced.

Subcooler - This is a section of some condensers in which the temperature of the condensed refrigerant liquid is reduced. This improves the energy efficiency of the chiller.

Thrust Bearing - A bearing which absorbs the axial forces produced in a centrifugal compressor by the refrigerant pressure differential across the impeller.

Ton - The English unit of measure for chiller capacity or refrigeration. One ton of refrigeration is the refrigeration produced by melting one ton of ice at 32 degrees F in 24 hours.

Turbine - A device mounted on a shaft extended from the end of the motor on Carrier 19XRT chillers. High pressure refrigerant liquid from the condenser flows through the turbine, causing it to turn, helping the motor to turn, thus reducing chiller operating energy. Carrier patented design.

Two Stage Centrifugal Compressor - Type of centrifugal compressor having two impellers. The first stage impeller raises the pressure of the refrigerant vapor approximately half way from the cooler pressure to the condenser pressure, and the second stage impeller raises the pressure the rest of the way. With a two stage compressor, an interstage economizer may be used to improve the refrigeration cycle efficiency.

UL - Underwriters' Laboratories

Vapor Compression Cycle - A refrigeration cycle consisting of a cooler, a compressor, a condenser, and an expansion device. In the cooler, heat is removed from the fluid being cooled by the boiling of liquid refrigerant into vapor. The compressor continuously draws this low pressure vapor from the cooler, and adds energy to the refrigerant, increasing its pressure and temperature, and discharges the high pressure vapor to the condenser. In the condenser, the cooling fluid removes heat from the refrigerant, which is condensed into liquid. The expansion device, which may be a float valve or an orifice, drops the pressure of the refrigerant liquid back down to cooler pressure.

Volume Index (volume ratio) - For screw compressors, this is the trapped volume existing at the beginning of the compression process divided by the reduced volume at the point of initial exposure to the discharge port.

Waterbox - For a shell and tube heat exchanger which has the water or brine flowing through the tubes, the waterbox is a chamber on each end of the shell into which all of the tubes empty. At the inlet end of the heat exchanger, an inlet nozzle (pipe) connects to the waterbox, and the fluid flows from the nozzle into the waterbox and into the first pass of the tubes; at the outlet end of the heat exchanger, an outlet nozzle connects to the waterbox, and the fluid flows from the last pass of the tubes into the waterbox and into the outlet nozzle.