Tech method lesson 1a.txt
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- tags "Cooling 101"
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- fileName "Tech method lesson 1a"
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- Tech method (introduction)
- Faulty / incomplete diagnosis is the underlying cause of most callback. Callbacks are the #1 enemy of the service technician.
- Callbacks eat up profits and destroy the reputation of both the service technician and contractor.
- Diagnosing systems is a process of elimination.
- Eliminate those portions of the system that are operating properly.
- You must be able to identify proper operation.
- T = temperature controls
- E = evaporating unit
- C = condensing unit
- H = Heat measurements
T = temperature controls
- Temperature controls can be electric electronic or pneumatic.
- Nothing happens until the temperature controls tell the system to start. This makes it the ideal place to start.
E = evaporating unt
- Evaporating unit consists of coil, fan, and duct work.
- Any obstruction system operation and will confuse your diagnostic efforts.
C = condensing unit
- Condensing unit consist of the outdoor coil, fan, compressor.
- Inadequate outdoor airflow will cause confusing symptoms to appear in various parts of the system.
H = heat measurements
- Superheat & sub cooling measurements are most accurate under design conditions.
- In cold ambient conditions it is necessary to raise the condensing temperature to at least 100 degrees before taking these measurements.
Excessive sub cooling caused by:
- Non-condensables (air)
- Restriction (normally at metering device)
- TXV; charge refrigerant through subcoolng.
- Fixed Orifice; charge refrigerant through superheat.
High superheat (based on txv/fixed orifice)
- High superheat caused by;
- Undercharge (leak),
Low superheat (based on fixed orifice)
- Low superheat is caused by;
- Overcharge (fixed orifice),
- Over feeding metering device (txv/fixed orifce),
- Inefficient compressor (fixed orifice)
- Low airflow gives low superheat,
- High airflow gives high superheat.
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