How do you determine a compressor failure root cause?

Summary:

The following key pieces of information must be gathered to help determine the root cause. This article can be used as a guideline and applies to various system types. Skip the sections that are not applicable. Additional information may be requested from technical support on a case-by-case basis.

Return the information below to CSTTechSupport@Trane.com and reference the CST number in the subject line.

Questions applicable to most failures:

1. If a compressor analysis is needed, cut the suction and discharge lines from the compressor. Do not crimp close the suction and discharge ports on the compressor to contain oil during transit. Reuse the plugs that ship with the new compressor or tape off openings in the field. The original compressor protection module must remain installed on the failed compressor.  
2. What is the unit being used for? Is it a surgical suite, School, office, process etc. 
3. Has there been any recent changes made to the system?
4. Forward service tickets from startup and other applicable service history if available.
5. How long was the compressor in service before the failure occurred?
6. Take a backup of the program and forensic package (Symbio and CH530 controlled units)
7. Provide the following information or use the last known data if possible.

8. Provide pictures or part numbers of the of the TXVs heads and body.

9. Verify the crank case heaters operate when compressor is off.

10. Provide picture of the failed compressor nameplate.

11. System refrigerant charge amount.

12. Oil level at time of failure.

     13. What was the cause of the failure? Select all that apply:

Questions applicable to VS Compressor:

1. Review the drive alarm history log and record events.
2. Verify the oil injection solenoid coil wiring connections and coil resistance.

 Questions applicable to air cooled systems:

1. Confirm outdoor fans are spinning correctly
2. Confirm blades are mounted properly
3. Confirm fans staged per the intended sequence (based on number of compressors, outdoor temperature, pressure etc.)

Questions applicable to AHUs:

1. Return Air Temperature
2. Supply Air Temperature
3. Indoor airflow

Questions applicable to split systems:

1. What are the line sizes, lengths, and riser heights? Take pictures of piping at the evaporator.
2.  Draw a sketch of field piping. Include refrigerant line diameters, line slope, indicate if lines are insulated or not, indicate where lines go underground, indoor to outdoor unit elevation difference, and traps.
3.  For split systems, take pictures of the terminals that the isolation valves are wired to.
4.  For split systems, how is the evaporator fan interlock accomplished?

Questions applicable to chillers and water-cooled systems:

1. Provide fluid test and balance report.
2. Provide fluid pressure drop on heat exchanger.
3. Does the flow switch function properly / free of debris?
4. Entering Fluid Temp
5. Leaving Fluid Temp
6. Fluid Pressure Drop

WARNING:

Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.