Commercial Refrigeration Application of Refrig. Sys. Chapter 26

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Commercial Refrigeration Application of Refrig. Sys. Chapter 26
2015-03-03 16:17:02
heat reclaim

different types of displays system,package vs remote, mullion heat, heat reclaim, various defrost,vending machine, walk in coolers,air-dry units
Show Answers:

  1. Reach in refrigeration are available in open and closed cases.
    temperature ranges are high, med, and low
  2. Self contained reach in
    • heat rejected in the store
    • can be moved
  3. individual condensing unit
    • can be moved to a equipment room
    • if one goes down only effect one system
    • rejected heat can be reclaimed
  4. Multiple evap & single comp. (Advantages)
    • heat can be reclaimed
    • compressors are larger more efficientd
    • cpr prevents hot pull downs
  5. Multiple evap & single comp (Disadvantages)
    • increased power consumption
    • higher locked rotor amps
    • short cycling
    • small increase in load, may cause comp. to cycle on
    • load can't be matched easily
  6. What two refrigerants are used in the coil for AC
    • R-22 
    • R-410a
  7. Heat reclaim coil will have what kind of refrigerant
    the same refrigerant that is used in the boxes of the store
  8. Parallel comp system
    • rack system
    • 2 or more comp
    • conn. with common suction line, discharge header, & reciever
    • PDV: Pressure Diff Valve, between the suction line & the oi reserve 5-20
  9. Advantages of the Parallel rack sys.
    • If one compressor fails,the others can     carry the load until repairs are made
    • Load matching
    • diverse
    • flexibility
    • high eff.
    • low compression cycling
  10. Disadvantage of a Parallel sys.
    • issues effect the entire rack
    • leaks
    • remote condenser unit failure
    • burn-outs
  11. Load Matching:
    • As the load changes, the common suction press entering the compressor will vary
    • actual load is sensed by a press transducer
    • compressor will cycle on or off depending on load
  12. Even system
    un-even system
    • same size compressor
    • different size compressor
  13. System Pressure Regulators (SPR)
    • Located between condenser & receiver
    • utilizes a parallel receiver
    • on hot days cause refrig to enter receiver to maximize condenser effective surface area
  14. Secondary fluid refrigeration sys.
    • primary sys. uses hfc or hcfc to cool secondary sys
    • secondary sys. uses glycol as refrigerant
    • heat exchange takes place between second and primary system
  15. Refracto meter
    is used two measure the glycol/water content percentage
  16. Advantages of Secondary refrigerant system
    • Uses less refrigerant
    • easier to install
    • uses pvc instead of copper
    • lower superheat
    • glycol is non toxic
    • becomes more cost effective over time
  17. Disadvantages of a secondary refrigerant system
    • higher initial investment
    • glycol os about $80.00 a gallon
    • holds about a 1000 gallons of glycol
  18. Pressurized liquid system
    • used on line sets over 100 feet
    • uses a centrifugal pump to pressurize line set
    • increases efficiency, by lower head pressure, condensing temp, compression ratio
  19. Unitary stand alone refrigeration system
    • multiple compressor modules, located close to display case
    • refrigerant usage is reduced
  20. evaporator temperature control
    • helps maintain box temp with no wiring
    • multiple evap may not operate at the same temp
    • evap press regulator can be used to maintain different pressure
  21. Temp box control of a Medium temp box
    • EPR: no wiring
    • Mechanical Timer: Planned defrost
    • Staggered: defrost can be timed at different times per box
  22. Temp control of a low temp box
    • heat must be supplied by electric or hot gas
    • heat from other boxes is used for hot gas defrost
  23. hot gas defrost
    • discharge gas from the compressor is directed to the evap being defrosted
    • the other evap can remain in the cooling mode while one evap is being defrosted
    • the evap in a defrost is piped in parallel to the compressor