Phase Loss RTAA

Issue:

Phase loss diagnostics on compressor A and/or B

Resolution:

1. Check wiring connections from starter to Current Transformers (CT's)
2. Checkout Current Transformers (CTs) and check resistance across each one while it is disconnected. All resistances should be within 10% of one another.
   1. Also do a diode test on the CT inputs on each compressor module. (The diode test is described in RTAA-SVB10B-EN.)
3. Check for a chattering or malfunctioning High Pressure Cutout (HPC).  Use a jumper temporarily to see if problem goes away.
4. Check for 120 volts at J7-3 on the compressor modules (1U4 or 1U5) when the compressor is trying to start.

5. Check the 1K2 Aux 2 (RUN) contact and 1K4 Aux1 (TRANSITION) contact for compressor A and the 1K6 Aux 2 (RUN) and 1K8 Aux1 (TRANSITION) contacts for compressor B. These should be a dead short, normally closed contacts.  If there is any amount of resistance, replace them.

6. Check for any swapping of 115 volt and neutral wiring on the 1U4/1U5

Notes:

The diode test is described in RTAA-SVB10B-EN

Resources Available:

• Tech TV Video(s):
  • N/A
• Reference Literature:
  (Electronic copies can be pulled from e-library at Trane Residential (tranetechnologies.com))
  • IOM: RTAA-SVX01A-EN
  • Troubleshooting Guide: RLC-SVD03A-EN
  • Compressor Module Troubleshooting: RTAA-SVB10B-EN
• Other:
  • N/A

Changes:

Other Question/Problem/Cause Statements:

• Getting phase loss diagnostics on compressor A and B.
• Phase loss diagnostics and Starter contactors will not pull in.
• Current Transformers (CTs) checked and resistance is ok.  Less than 0.1 Ohm variation between each one and they are the same resistance as the other circuit's CTs.
• Replaced 1U4 compressor module.

Facts:

• RTAA 70-125 TON (PUEBLO)
• Air-Cooled Chiller (Pueblo) (RTAA 70-125 Ton)
• Compressor Chiller (Pueblo) (RTUA)
• Water-Cooled Chiller (Pueblo) (RTWA)

Document Identifier: DOC-93151