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The flashcards below were created by user
salvatorefricano
on FreezingBlue Flashcards.
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Reach in refrigeration are available in open and closed cases.
temperature ranges are high, med, and low
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Self contained reach in
- heat rejected in the store
- can be moved
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individual condensing unit
- can be moved to a equipment room
- if one goes down only effect one system
- rejected heat can be reclaimed
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Multiple evap & single comp. (Advantages)
- heat can be reclaimed
- compressors are larger more efficientd
- cpr prevents hot pull downs
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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
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What two refrigerants are used in the coil for AC
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Heat reclaim coil will have what kind of refrigerant
the same refrigerant that is used in the boxes of the store
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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
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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
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Disadvantage of a Parallel sys.
- issues effect the entire rack
- leaks
- remote condenser unit failure
- burn-outs
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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
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Even system
un-even system
- same size compressor
- different size compressor
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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
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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
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Refracto meter
is used two measure the glycol/water content percentage
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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
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Disadvantages of a secondary refrigerant system
- higher initial investment
- glycol os about $80.00 a gallon
- holds about a 1000 gallons of glycol
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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
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Unitary stand alone refrigeration system
- multiple compressor modules, located close to display case
- refrigerant usage is reduced
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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
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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
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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
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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
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