Tech method lesson 2B.txt
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- 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.
- 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.
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.
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)
The evaporaing temperature should be at least 35 dgrees below the space temperature at design conditions.
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