Tech method lesson 2B.txt

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Tech method lesson 2B.txt
2013-05-24 06:50:19


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    • author "me"
    • tags "Cooling 101"
    • description ""
    • fileName "Tech method lesson 2B"
    • freezingBlueDBID -1.0
    • Low superheat
    • Only a low superheat measurement can indicate flood back.
    • Superheat tells us if there is too much or not enough refrigerant on the low side of the system.
  1. Heat load
    • Anything which adds heat to the evaporator will boil off more refrigerant.
    • Anything which interferes with the coils ability to absorb heat will lower the superheat.
    • We must check the evaporator fan, motor, coil, filter, and airflow before measuring the superheat.
  2. Compressor vacuum test
    • Reciprocating compressor only
    • Shut off the flow to the metering device via the liquid line service valve.
    • Can shut off suction as long as you have a true suction port (HP must hold RV in position).
    • Compressor should be able to pump 15" ~ 20" of vacuume and jold.
    • Ensure condenser can hold total refrigerant charge.
  3. Symtoms of an inefficient compressor
    • Low discharge pressure
    • High suction pressure
    • Low superheat
    • Low subcooling
    • Equalized pressure (no pump cmpressor)
    • Low evaporator t.d.
    • Low condenser t.d.
    • Will not pump down
    • Will not hold vaccume when pumping down.
    • Will not build head pressure (disconnect outdoor fan)
    • Low compressor amperage.
    • Compressor too quite or too loud. (Mechanical failure)
  4. Evaporator temperature
    The evaporaing temperature should be at least 35 dgrees below the space temperature at design conditions.