Low refrigerant temperature CGAM

Issue:

Low refrigerant temperature

Resolution:

CGAM chillers:

Low Refrigerant Temperature: The suction saturated refrigerant temperature dropped below the Low Refrigerant Temperature Cutout setpoint for 30F-sec (IOM CG-SVX17N-EN)

Causes for Low Evaporator Temperature include:

• Bad Suction Temperature Sensor (intermittent), Bad Suction Pressure Transducer
• EXV issues
• Low Water Flow-Verify design flow
• Low Refrigerant charge: Verify Subcooling (15-20 F) and EXV 40-50% open at full load, 12 F superheat; Ratio= EXV % flow command / Superheat Control Compressor Flow estimate > 1.6
• Incorrect Setting of Low refrigerant Temp Cutout (IOM). It should be set for type and percent (%) of glycol concentration

Approach Temperature is the difference between the Evaporator Leaving

Water Temperature (EWLT) and the Saturated Refrigerant Temperature

Its value represents the efficiency of the Braze plate heat exchanger.

The lower the value, the better efficiency

High approach temperatures can be the result of:

- Fouled evaporator, broken or by-passed water strainer. Flush evaporator water side with hot water

- Bad Suction Pressure Transducer, bad leaving water temperature Sensor

- Cross Bind sensors between circuits

- Water Flow too low

- High concentration of glycol

- Bad Suction Temp Sensor

- EXV malfunction

Note: For 40T chiller Expect 3 - 4 ⁰ F more in approach temperature

Resource Available:

• Tech TV Video(s):
  • N/A
• Reference Literature: (Electronic copies can be pulled from e-library at Trane Residential (tranetechnologies.com))
  • IOM: CG-SVX17N-EN
  • Service Guide: 
• Other:
  • N/A

Other Question/Problem/Cause Statements:

• Low evaporator temp cut out
• Low Refrigerant Temperature
• High Approach
• Why this chiller has high approach?

Facts:

• Chiller has high approach temperature. Approach was 35F
• Air-Cooled Chiller (Pueblo) (CGAM 20-130 Ton)

Original HUB Document: DOC-105515