HVAC Central

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Anonymous
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270389
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HVAC Central
Updated:
2014-04-12 23:29:47
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HVAC
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Central AC definitions
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  1. Chillers

    A fluid that absorbs heat by evaporation at a low temperature and pressure and releases heat by condensing at a higher temperature and pressure
    Refrigerant
  2. Water or glycol mixture that is cooled by a refrigerant, which is then circulated by pumps throughout the refrigeration system to absorb heat.  (a secondary refrigerant is used because it is cheaper and safer, as opposed to circulating refrigerant).
    Secondary Refrigerant
  3. Variable Frequency Drive
    VFD
  4. Pie shaped dampers, used on centrifugal compressors used to direct gasses into the compressor and used for capacity control.  (The compressor will start with guide vanes closed=unloaded position)
    Pre-rotation guide vanes
  5. Know a dry type evaporator, this evaporator will boil a refrigerant and superheat that refrigerant before leaving the evaporator.
    Dry-type evaporators
  6. An evaporator that has water in the tubes and the tubes are submerged in refrigerant.  This allows for better heat transfer.  A flooded evaporator will use more refrigerant than a dry type evaporator.
    Flooded Evaporator
  7. A water box on a chiller or condenser with a removable cover.
    Marine water boxes
  8. The difference in temperature between the refrigerant and the leaving ater in a chilled-water system.
    Approach temperature
  9. The process by which one substance is absorbed by another
    Crystallization
  10. A term used to adjust the charge in an absorption chiller
    Trim
  11. Lithium-Bromide, a type of salt solution used in an absorption chiller.
    Li-Br
  12. Pumps

    Rotating part of a centrifugal compressor, pump or other machine which uses centrifugal force to move or compress a fluid.
    Impeller
  13. This is the housing that surrounds the impeller and guides the water through the water through the pump.
    Volute
  14. Centrifugal pump which has its inlet and its discharge in a straight line.
    In-line pump.
  15. Raises fluid pressure within the piping system, used to overcome resistance within the piping.
    Booster pump
  16. These pumps recirculate water throughout the system and coil/terminal units to transfer more heat from the water.
    Circulating pump
  17. These types of pumps are mounted directly to the motor shaft.
    Closed-coupled
  18. These types of pumps are mounted on an impeller shaft connected to the motor by a flexible coupling.
    Flexible-coupling
  19. Water within this system will come in contact with the atmosphere.  An example would be an open cooling tower.
    Open piping system
  20. Water within this system will not come in contact with the atmosphere.  Most chilled and hot water systems are closed systems.
    Closed System
  21. Air Handling Units and Piping systems

    This converts energy from electricity or fuel and is the source of hot or chilled water.  These are boilers and chillers within a system.
    Primary System
  22. This is known as the distribution system.  This delivers the heating or cooling throughout the building.
    Secondary system
  23. Return Air
    RA
  24. Exhaust Air
    EA
  25. Outside Air
    OA
  26. Mixed Air
    MA
  27. Are devices that are used to transfer heat from the stream or water to the surrounding air.  THis would be baseboard, radiator, unit heater, fan coil, or any other device that exchanges heat.
    Terminal Units
  28. This is the simplest design, all water flows through each terminal unit.
    Series loop
  29. This system is designed with supply and branch pipes and valves seaperate each terminal unit from the main supply line.  These systems require diverting tees to help with flow through the terminal units.
    One-pipe system
  30. This design uses a supply line and a return line to improve terminal unit efficiency by having each terminal unit receive water directly from the supply line.  The firs supplies, is the first returned.  (Water tends to cycle with design).
    Two pipe direct return
  31. This design is where flow resistance is directly proportional to the pipe length.  This is a better balanced system.  The first supplied is the last returned.
    Two-pipe reverse return
  32. A system where one pipe supplies chilled water and another supplies hot water and uses one pipe to return the water.  There are also three pipe systems that are changed over in the mechanical room.  This allows the system to supply heating or cooling by changing over the primary source.
    Three pipe system
  33. A system that supplies hot and chilled water all season long with each having their own return line to their primary source.  This allows the most flexibility for a building, but is the most expensive to install.
    Four pipe system
  34. Make-up Air (MUA)

    This Type of make-up air allows the air to come in contact with the flame to exchange heat.  This style does not have a heat exchanger.
    Direct fired
  35. This type of make-up air has a heat exchanger.  The products of combustion do not come in contact with the make-up air.
    In-direct fired
  36. A system that allows an additional item to get and/or become energized when needed.
    Interlocked

  37. A thermostat that is installed in a make-up air to prevent incoming air that is below freezing to continue to be supplied to the space.
    Freeze-stat
  38. The temperature of the air entering a make-up air unit.
    Inlet temperature
  39. The temperature of the air leaving the make-up air
    Discharge temperature
  40. Boilers

    Maximum Allowable Working Pressure
    MAWP
  41. A boiler design with water in the tubes surrounded by fire. 
    Water tube boiler
  42. A boiler design with fire in the tubes surrounded by surrounded by water. 
    Fire tube boiler
  43. American Society of Mechanical Engineers
    ASME
  44. Normal Operating Water Level
    NOWL
  45. WWSD
    Warm Weather Shutdown
  46. A valve on the boiler used to release air from the boiler when filling the boiler.
    Boiler Vent
  47. A system that "feed" water to the boiler at the correct pressure and temperature.
    Boiler feed water system
  48. Removers sludge build-up from the bottom of the boiler.
    Bottom blowdown
  49. Allows a continuous trickle of blowdown water from the boiler.
    Continuous blowdown
  50. Removes impurities from the surface water of a boiler system.
    Surface blowdown
  51. Cooling Tower
    When water and air come into contact and sensible heat is exchanged for latent heat.
    Evaporative cooling
  52. When air comes in direct contact with the water being cooled.
    Direct contact
  53. Whenever a wetted surface is used to faciltate heat transfer to another medium. 
    In-direct contact
  54. When air and water flow is in the same direction while traveling through the tower.
    Parallel flow
  55. When the water flows from the top to the bottom of the tower.  Fans draw in from the sides of the tower and discharge it from the top.
    Cross-flow
  56. The flow of the water is opposite the flow of the air as they travel through the fill section.
    Counter-flow
  57. When air is moved by pulling it through the tower.
    Induced draft
  58. When air is blowing into the tower by mechanical means.
    Forced draft
  59. When a amount of water is drained from the tower sump to remove minerals left behind as a result of water that has evaporated.
    Blow-down cycle
  60. Is a column of moisture rising in the atmosphere.
    Plume
  61. Is the undesirable loss of water within the atmosphere.
    Drift
  62. A type of control that is used for towers, with or without fans, as a means of controlling the cooling tower at low ambient conditions.
    Valve control
  63. Is when when a portion of the water is directed two inlets and one outlet.
    Diverting valve
  64. A whirlpool action action in the sump of a cooling tower.
    Vortexing
  65. Fire/Smoke Dampers-Fans

    Temperature rate link used on fire dampers.
    Fusible link
  66. A fan that forces the air in a radical direction perpendicular to the fan shaft.
    Centrifugal fan
  67. A design which air enters and exits the impeller along the same axis paralles to the fan's shaft.
    Axial fan
  68. A fan in which it discharges its air upward.
    Up-blast
  69. Air station and pneumatics
    Lines that supply supply air from the air station to the controller.
    Pneumatic Main Lines
  70. Lines that supply air from the controller to actuator.
    Pneumatic Branch Lines
  71. When the temperature is increased pressure is increased.
    Direct Acting
  72. When the temperature is increased pressure is decreased.
    Reverse Acting
  73. A range in which in which an actuator will move from the full open  or closed position.
    Spring Range
  74. A compressor and associated parts needed to supply clean dry air for pneumatic control.
    Air Station

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