INTRODUCTION TO HVAC SYSTEMS - AirTight

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INTRODUCTION TO HVAC SYSTEMS - AirTight Powered By Docstoc
					Introduction to HVAC Systems
      Presented by AirTight University
                HVAC User’s Guide

                       Objectives
Gain a better understanding of the basic concept
of air conditioning & air distribution

Review different types of units
   Split-systems
   Chilled Water Systems
   Packaged Units
   VAV – Variable Air Volume
   PIU – Powered Induction Unit
   CRAC & CRAH – Computer Room Air Conditioners & Air Handlers

Review the common components of each unit

Review basic HVAC terms
            Basic Components
Air Conditioners and all refrigeration systems
  have Four main components:

-   Compressor
-   Condenser
-   Metering Device
-   Evaporator
                       Basics of Refrigeration Cycle

                               Metering Device
Low pressure, liquid                             High pressure, liquid refrigerant
(gaseous mist) refrigerant                       from condenser coil to
from expansion valve to                          expansion valve
evaporator coil



                                                             Condenser
        Evaporator




                                                   High temperature,
Low pressure gas taking heat
from evaporator to                                 high pressure,
compressor                      Compressor         gaseous refrigerant
                                                   from compressor to
                                                   condenser coil
     Common Systems in Data Centers
                  Legacy Design (Raised Floor)

Condensers
– Water or
Air-Cooled


                                                 Warm Return Air




                                                  Air Handler
Cold Supply Air
                          Typical Rooftop Packaged Unit
                                    Condenser Fan Motor & Blade assembly
                                            10

1. Compressor
2. Evaporator Coil
3. Condensate Pan
4. Gas & Electrical connectors to roof
5. Control Board
6. Heat Exchanger
7. Base rail
8. Condenser fan motor
9. Belt drive blowers
10. Condenser Fan Motor & Blade


                                                               Draft Inducer Motor assembly
        VAV – Variable Air Volume Box
                                                        Precision
                                   Self lubricating
                                                        machined
           Insulation is 1”,       nylon bearings                           Damper design features a full
                                                        zinc plated
           two pound density       for long life and                        diameter contact seal that
                                                        solid steel
           and complies with       reliable low                             maintains less than 1% air
                                                        shaft
           UL 181 and NFPA         friction operation                       leakage at pressures up to 4”
           90A requirements                                                 water gauge
       Seismic tabs are
       standard for
       easy installation                                                         S & Drive connection for
                                                                                 rapid field installation


Inlet sized to fit                                                                  Shaft indicator shows damper
all standard                                                                        position
round ducts

                                                                                      Direct drive, rack & pinion
                                                                                      actuator maintains precise
                                                                                      control by eliminating
        Multipoint averaging                                                          hysteresis and blade
        velocity sensor                                                               vibration
        amplifies airflow signal
        for greater accuracy             Gauge taps for               Controller allows for
                                         direct flow                  maximum-minimum
                                         measurement and              design settings,
                                         field balancing              pressure independent
                                                                      control
                                       PIU – Powered Induction Box

Internal electric, hot water or steam heat to allow for staging
of heat in conjunction with the fan running
 and the cooling damper closing off.


       Internal electric
       fan to provide
       recirculated air
       as the first stage
       of heat,                                                                            Multipoint averaging
       generally used                                                                      velocity sensor
       for perimeter                                                                       amplifies airflow signal
       zones                                                                               for greater accuracy

           Insulation is 1”,                                                              Direct drive, rack & pinion
           two pound density                                                              actuator maintains precise
           and complies with                                                              control by eliminating
           UL 181 and NFPA                                                                hysteresis and blade
           90A requirements                                                               vibration

                               Damper design features a full
                               diameter contact seal that         Controller allows for      Inlet sized to fit
                               maintains less than 1% air         maximum-minimum            all standard
                               leakage at pressures up to 4”      design settings,           round ducts
                               water gauge                        pressure independent
                                                                  control
    CRAC - Computer Room Air Conditioner
    & CRAH – Computer Room Air Handler
A computer room air conditioning (CRAC or CRAH) unit is a device that monitors and maintains the
temperature, air distribution and humidity in a computer room or data center. As the I.T. industry
grows, so does the need for removing the heat from the mission critical facilities. Mainframes and
racks of servers can get as hot as a seven-foot tower of powered toaster ovens, so climate control is
important part of the data center's infrastructure.

One configuration that has been successful is the process of cooling air and having it dispensed
through an elevated floor. The air rises through the perforated sections, forming cold aisles. The cold
air flows through the racks where it picks up heat before exiting from the rear of the racks. The warm
exit air forms hot aisles behind the racks and the hot air returns to the unit intake, which are
positioned above the floor. The inverse concept can be utilized with an overhead delivery as well.
Common Parts
                            Evaporator Coil
 Expansion Valve




                   Liquid
                   Line
                   Drier
                Types of Condensers
             Typical Critical Systems Remote Condensers




                                                          Mini Split



Typical condenser– Residential of office
         Condensing Unit Components
                         Fan Motor
                             &
                           Blade
Condensing Coil
                      1 – Fan Blade
                      2 – Protective Cover
                         (Rain Shield)
                      23 – Fan Motor
                      24 – Sheave
                      25 - Shaft




  Filter Line Dryer
                      compressor
          What does this “stuff” do?
• The Condensing Unit – The condensing unit is located outdoors and is
  responsible for removing the heat that was captured indoors. A
  compressor, located within the condensing unit, circulates the refrigerant
  throughout the system.
• The Remote Condenser – The heat rejection component that dissipates
  heat when the compressor is with the CRAC unit.
• The Condenser Fan – As refrigerant travels through the condenser coil it
  begins to cool down. A fan blowing across this condenser coil speeds up
  this process and is critical in facilitating the transfer of heat to the outside
  air.
• Filter Dryer – Removes impurities and moisture that could be in the
  refrigerant system.
                Types of Compressors

Reciprocating Compressor          Scroll Compressor




                                  Centrifugal
Screw Compressor                  compressor




   Rotary Compressor       Oil-less Compressor
     What does a Compressor do?
• The purpose of the compressor is to pump refrigerant
  vapor/gas through the system and create a pressure
  differential. A metering device creates the restriction needed
  to separate the high side pressure from the low side pressure.
  High pressure, hot gas is pumped out of the compressor and is
  cooled into a high pressure liquid by the time it leaves the
  condensing coil. This liquid is fed through a metering device
  into the evaporator coil and turns into a low pressure gas by
  the time it leaves. It returns to the compressor as a low
  pressure gas ready to repeat the process.
             Types of Air Handlers
                                           CRAC / CRAH Air Handlers




                                                             Wall Mount
Typical Residential / Indoor Air Handler
      Components of an Air Handler
            Contactors and Relay’s
                                                        Circuit Board

Disconnect Switch



  Line Driers
                                                              Evaporator Coil


 Compressors




                    Blower                          Pulley, Shaft and Sheave
                                     Blower Motor
    What does the Air handler Do?
• The Air handler absorbs heat and removes humidity. It houses the filters,
  blower and evaporator. The refrigerant circulating through the evaporator
  coil absorbs heat as warm air travels across it. Humidity also collects on
  the cold surface of the evaporator and drains down the coil and collects in
  a drain pan and is disposed of down the condensate drain.
• The air handler draws filtered air over the evaporator coil.
• The cooler drier air gets pushed through the duct work by the blower and
  is diffused throughout the designated space to maintain the desired
  temperature and humidity levels within that designated space.
So how do these systems work
         together?
Cooling Towers
Cooling Tower Types
                           Chillers
• Water chillers are everywhere - they are used to air condition
  large industrial, commercial and institutional facilities and are
  used to lower the temperatures of all kinds of equipment,
  from machinery to computer parts and server racks.
• Basically, the principal is, the chiller removes heat from (cools)
  a liquid, usually water, then circulates the cooled liquid
  through a chilled water circuit to provide cooling to each of
  the connected air handling units. CRAH units utilize this
  technology in many applications.
The entire system working together
              Economizers




Free cooling box           Outdoor type packaged A/C
                               Installed in Shelter

 Applied in the shelter air conditioning unit
             Energy saving: 15%-50%
The Reasons for Economizers are Many
• To lower the total cost of ownership – In many locations there is a
  substantial opportunity for OpEx savings over the life of the equipment
  operation. This is largely due to the 365x7x24 operation of the facilities
  and cooling needs. When ever economizers are operating (making use of
  outside air temperatures) mechanical cooling is not required.
    – Makes use of the colder outside air to cool the indoor space. Bot outdoor temperature
      and outdoor humidity can play a key role in when an economizer would operate.
• Reduced CapEx by increased service life of the mechanical equipment.
  When economizers are in full economizer mode, compressors are not. This
  reduces the amount of run hours of the equipment. Equipment life can be
  doubled in some cases.
• Reduced OpEx associated with the refrigerant circuit (compressor, etc.) –
  same as item 2 above.
Economizers = savings!
Definition of Common
HVAC Technical Terms
                                  HVAC terms
•   Acid Condition in System – Condition in       •   Back Pressure – Pressure in low side of
    which refrigerant or oil in system is             refrigerating systems; also called
    mixed with fluids that are acid in nature.        suction pressure or low-side pressure.
•   Actuator – That portion of a regulating
                                                  •   Bearing – Low friction device for
    valve which converts mechanical fluid,
    thermal energy, or electrical energy into         supporting and aligning a moving part.
    mechanical motion to open or close the        •   Belt – a rubber-like, continuous loop
    valve seats.                                      placed between two or more pulleys to
•   Air Diffuser – Air distribution outlet or         transfer rotary motion.
    grille designed to direct airflow into        •   Boiler – Closed container in which a
    desired patterns.                                 liquid may be heated and vaporized.
•   Air Handler – Fan-blower, heat transfer
                                                  •   Brazing – Method of joining metals
    coil, filter and housing parts of a system.
                                                      with nonferrous filler (w/out iron) using
•   Air Cooled Condenser – Heat of
                                                      heat between 800F (427C).
    compression is transferred from
    condensing coils to surrounding air. This     •   Btu-British Thermal Unit – Quantity of
    may be done either by convention or by            heat required to raise temperature of
    a fan or blower.                                  one pound of water one degree
                                                      Fahrenheit.
                                 HVAC terms
•   Capacitor – Type of electrical storage     •   Condensate – A fluid formed when a
    device used in starting and/or running         gas is cooled to its liquid state.
    circuits on many electric motors.
                                               •   Condensate Pump – Device to remove
•   Capacity – Refrigeration rating system.        water condensate that collects
    Usually measured in Btu per hour or            beneath an evaporator.
    watts (metric).
                                               •   Condensation – Liquid or droplets
•   Charge – Amount of refrigerant placed          which from when a gas or vapor is
    in a refrigerating unit.                       cooled below its dew point
•   Circuit – Tubing, piping or electrical     •   Condenser, Air-Cooled – Heat
    wire installation which permits flow to        exchanger which transfers heat to
    and from the energy source.                    surrounding air.
•   Circuit Breaker – Safety device that       •   Condenser, Water – Cooled – Heat
    automatically open an electrical circuit       exchanger designed to transfer heat
    if overloaded.                                 from hot gaseous refrigerant to water.
•   Compressor – Pump of a refrigerating       •   Condenser Coil – Made of copper
    mechanism which draws a low                    tubing, this is where the hot Freon is
    pressure on cooling side of refrigerant        compressed to squeeze the heat out
    cycle and squeezes or compresses the           of it.
    gas into the high-pressure or
    condensing side of the cycle.
                              HVAC terms
•   Condenser Fan – Forced air device         •   Control, Low-Pressure – Cycling device
    used to move air through air-cooled           connected to low-pressure side of
    condenser.                                    system.
•   Condenser Fan Motor – Enables fan to      •   Cooling Tower – Device which cools by
    blow air across the surface of the            water evaporation in air. Water is
    Condenser coil carrying away the heat.        cooled to wet bulb temperature of
•   Condensing Pressure – Pressure inside         air.*****
    a conde3nser at which refrigerant         •   Cut-In – The temperature value or the
    vapor gives up its latent heat of             pressure value at which the control
    vaporization and becomes a liquid.            circuit closes
    This varies with the temperature.         •   Cut-Out – Temperature value or
•   Condensing Temperature –                      pressure value at which the control
    Temperature inside a condenser at             circuit opens.
    which refrigerant vapor gives up its      •   Cycle – Series of events or operations
    latent heat of vaporization and               which have tendency to repeat in the
    becomes a liquid. This varies with            same order.
    pressure.
•   Condensing Unit – Part of a
    refrigerating mechanism which pumps
    vaporized refrigerant from the
    evaporator, compresses it, liquefies it
    in the condenser, and returns it to the
    refrigerant control.
                                  HVAC terms
•   Damper – Device for controlling airflow.         •   Evaporator – Part of a refrigerating
•   Defrost Cycle – The process of removing ice          mechanism in which the refrigerant
    or frost buildup from the outdoor coil during        vaporizes and absorbs heat.
    the heating season.                              •   Evaporator Coil – Typically made of
•   Detector, Leak – Device used to detect and           copper, carries cold gaseous Freon
                                                         that absorbs heat from air traveling
    locate refrigerant leaks.                            over the surface of the coil.
•   Drier- Substance or device used to remove        •   Evaporator Fan – Fan which increases
    moisture from a refrigeration system.                airflow over the heat exchange surface
•   Drip Pan – Pan-shaped panel or trough used           of evaporators.
    to collect condensate from evaporator.           •   Expansion Valve – Device in
•   Duct – Tube or channel through which air is          refrigerating system which reduces the
    conveyed or moved.                                   pressure from the high side to the low
                                                         side and is operated by pressure.
•   Enthalpy – Total amount of heat in one           •   Fan – Radial or axial flow device used
    pound of a substance calculated from                 for moving or producing flow of gases.
    accepted temperature base. Temp of 32F           •   Filter – Device from removing small
    (0C) is accepted base for water vapor                foreign particles from fluid or air.
    calculation.                                     •   Flexible Duct – A duct that can be
•   Evaporation – Term applied to the changing           routed around obstacles by bending it
    of a liquid to a gas. Heat is absorbed in this       gradually.
    process
                            HVAC terms
•   Float Valve – Type of valve which is       •   Gasket – Resilient (spongy) or flexible
    operated by sphere or pan which floats         material used between mating
    on liquid surface and controls level of        surfaces of refrigerating unit parts.
    liquid.                                    •   Grille – Ornamental or louvered
•   Freeze-Up – 1) Formation of ice in the         opening placed in a room at the end of
    refrigerant control device which may           an air passageway.
    stop the flow of refrigerant into the      •   Head Pressure – Pressure which exists
    evaporator. 2) Frost formation on an           in condensing side of refrigerating
    evaporator which may stop the airflow          system.
    through the evaporator.                    •   Head Pressure Control – Pressure
•   Freon – Trade name for a family of             operated control which opens
    synthetic chemical refrigerants                electrical circuit if high-side pressure
    manufactured by the DuPont Company.            becomes too high.
•   Fuse – Electrical safety device            •   Head Pressure Safety Cut-Out Motor
    consisting of strip of fusible metal in        protection device wired in series with
    circuit which melts when circuit is            motor; will shut off the motor when
    overloaded.                                    excessive head pressures occur.
•   Gas Valve – Device in a pipeline for
    starting, stopping or regulating flow of
    gas.
                           HVAC terms
•   Heat Exchanger – Device used to        •   Humidity – Moisture dampness of air.
    transfer heat from a warm or hot
                                           •   Junction Box – Box or container housing
    surface to a cold or cooler surface.
                                               group of electrical terminals.
    (Evaporators and condensers are heat
    exchangers.                            •   Liquid Line – Tube which carries liquid
                                               refrigerant from the condenser or liquid
•   Heat Load – amount of heat, measured
                                               receiver to the refrigerant control
    in Btu or watts, which is removed
                                               mechanism.
    during a period of 24 hours.
                                           •   Low Pressure Safety Cut-Out – Motor
•   Heat Pump – Compression cycle system
                                               protection device that senses low-side
    used to supply heat to a temperature-
                                               pressure.
    controlled space. Same system can also
    remove heat from the same space        •   Moisture Indicator – Instrument used to
                                               measure moisture content of a
•   High Pressure Cut-Out – Electrical
                                               refrigerant.
    control switch operated by the high-
    side pressure which automatically      •   Motor – Rotating machine that transforms
    opens electrical circuit if too high       fluid or electric energy into a mechanical
    pressure is reached.                       motion.
                                HVAC terms
•   Motor Burnout – Condition in which         •   Overload – Load greater than that for
    the insulation of an electric motor has        which system or mechanism was
    deteriorated.                                  intended
•   Motor Control – Device to start and/or     •   Overload Protector – Device, either
    stop a motor at certain temperature            temperature, pressure, or current
    or pressure conditions.                        operated, which will stop operation of
•   Motor Starter – high-capacity electric         unit if dangerous conditions arise.
    switchers usually operated by              •   Package Units – Complete refrigerating
    electromagnets.                                system including compressor,
•   Oil, Refrigeration – Specially prepared        condenser, and evaporator located in
    oil used in refrigerator mechanism             the refrigerated space.
    which circulates, to some extent, with     •   Pressure Switch – Switch operated by
    refrigerant.                                   a rise or drop in pressure.
•   Open Circuit – Interrupted electrical      •   PSI – Symbol or initials used to
    circuit which stops flow of electricity.       indicate pressure measured in pounds
•   Operating Pressure – Actual pressure           per square inch.
    at which the system works under
    normal conditions. This pressure may
    be positive or negative. (vacuum).
                                 HVAC terms
•   Pulley – Flat wheel with a “V” groove.     •   Refrigerant Dye – Coloring agent that
    When attached to a drive and drive             can be added to refrigerant to help
    members, the pulley provides a means           locate leaks in a system.
    for driving the compressor or blower
    wheels. (AKA Sheave)                       •   Refrigerant Reclaim – To reprocess
•   Purging – Releasing compressed gas to          refrigerant to new product
    atmosphere through some part or parts          specifications. This will require chemical
    for the purpose of removing                    analysis, and usually refers to the
    contaminants from that part of parts.          processes available at a reprocessing or
•   Refrigerant – Substance used in                manufacturing facility.
    refrigerating mechanism. It absorbs        •   Refrigerant Recovery – To remove
    heat in evaporator by change of state          refrigerant and place in a cylinder
    from a liquid to a gas, and releases its       without necessarily testing it.
    heat in a condenser as the substance
    returns from the gaseous.                  •   Refrigerant Recycling – To remove
•   Refrigerant Control – Device which             refrigerant and place in a cylinder
    measures flow of refrigerant between           without necessarily testing it.
    two areas of a refrigerating system. It    •   Refrigerant Recycling – To clean
    also maintains pressure difference             refrigerant fro reuse by reducing
    between high-pressure and low-                 moisture, acidity and matter. Usually
    pressure side of the mechanical                applies to procedures at job site or local
    refrigerating system while unit is             service shop.
    running.
                                  HVAC terms
•   Register – Combination grille and
                                                  •   Reversing Valve – Device used to reverse
    damper assembly covering an air                   direction of the refrigerant flow,
    opening or the end of an air duct.                depending upon whether heating or
•   Relay – An electromagnetic                        cooling is desired.
    mechanism moved by a small                    •   Safety Control – Device to stop
    electrical current in a control circuit. It       refrigerating unit if unsafe pressure,
    operates a valve or switch in an                  temperatures, and/or dangerous
    operating circuit.                                conditions are reached.
•   Relief Valve – Safety device on a             •   Safety Motor Control – Electrical device
                                                      used to open circuit to motor if
    sealed system. It opens to release
                                                      temperature, pressure and/or current
    fluids before dangerous pressure is               flow exceed safe conditions.
    reached.
                                                  •   Safety Valve – Self-operated, quick
•   Remote System – Refrigerating system              opening valve used for fast relief of
    in which condensing unit is away from             excessive pressures.
    space to be cooled.                           •   Schrader Valve – Spring-loaded device
•   Retrofit – Term used in describing                which permits fluid flow in one direction
    reworking an older installation to                when a center pin is depressed and in
    bring it up to date with modern                   other direction when a pressure
                                                      difference exists.
    equipment or to meet new code
    requirements.
                               HVAC terms
•   Sensor – Material or device which
    goes through physical change or             •   Slugging – Condition in which mass of
    electronic characteristic change as             liquid enters compressor causing
    surrounding conditions change.                  hammering.
•   Service Valve – Manually operated           •   Soldering – Joining two metals by
    valve mounted on refrigerating                  adhesion of a metal with a melting
    systems used for service operation.             temperature of less than 800F. (427C)
•   Short Circuit – Electrical condition        •   Solenoid Valve – Electromagnet with a
    where part of circuit touches another
                                                    moving core. It serves as a valve or
    part of circuit and causes all or part of
    current take wrong path.                        operates a valve.
•   Short Cycling – Refrigerating system        •   Split System – Refrigeration or air
    that starts and stops more frequently           conditioning installation, which places
    than it should.                                 condensing unit outside or away from
•   Shroud – Housing over condenser,                evaporator. Also applicable to heat
    evaporator or fan.                              pump installations.
•   Sight Glass – Glass tube or glass           •   Squirrel Cage – Fan which has blades
    window in refrigerating mechanism. It           parallel to fan axis and moves air at
    shows amount of refrigerant or oil in           right angles or perpendicular to fan
    system and indicates presence of gas            axis.
    bubbles in liquid line.
                               HVAC terms
•   Suction Line – Tube or pipe used to       •   Thermocouple - Device which generates
    carry refrigerant gas from evaporator         electricity, using principle that if two
    to compressor.                                unlike metals are welded together and
•   Suction Pressure Control Valve – Two-         junction is heated, a voltage will develop
    way, manually operated valve located          across the open ends.
    at the inlet to compressor. It controls
    suction gas flow and is used to service   •   Thermostat – Device which senses
    unit                                          ambient temperature conditions and, in
•   Suction Side – Low-pressure side of           turn, acts to control a circuit.
    the system extending from the             •   Thermostatic Expansion Valve (TXV) –
    refrigerant control through the               Control valve operated by temperature
    evaporator to the inlet valve of the          and pressure within evaporator. It
    compressor.                                   controls flow of refrigerant. Control bulb
•   Superheat – 1) Temperature of vapor           is attached to outlet of evaporator.
    above its boiling temperature as a
    liquid at that pressure. 2) The           •   Transformer – Electromagnetic device
    difference between the temperature            which transfers electrical energy from
    at the evaporator outlet and the lower        primary circuit into variations of voltage
    temperature of the refrigerant                in secondary circuit.
    evaporating in the evaporator.
                            HVAC terms
•   Vacuum Pump – Special high
    efficiency device used for creating high   • Velocity – Quickness or rapidity of
    vacuums for testing or drying                 motion, swiftness, speed.
    purposes.                                  • Ventilation – Forced airflow, by
•   Valve – Device used for controlling           design, between one area to another.
    fluid flow.
•   Vapor Lock – Condition where liquid
    is trapped in line because of bend or
    improper installation. Such vapor
    prevents liquid flow.
•   VAV- Variable air volume.
•   V-Belt – Type of belt commonly used
    in refrigeration work. Has a contact
    surface with a pulley which in the
    shape of a V.
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