Trane CGAM Air-Cooled Scroll Chiller Startup Procedure

Why this matters

A Trane CGAM (model RTAC-CGAM, 20 to 130 tons nominal, R-410A scroll compressors) that is energized before pre-startup checks complete will trip the lockout on its first call to cool, and the field tech then spends a day re-checking what should have been verified before electrical connection. The Trane Tracer UC400 controller logs the trip and Trane warranty will reject claims where the commissioning checklist was not completed and signed. The factory startup procedure (Trane SVC IOM CG-SVX17H-EN, current revision) is not optional for warranty registration.

Pre-startup mechanical checks

Complete these before any electrical connection beyond the disconnect:

1. Verify equipment matches the submittals: model number on the nameplate, refrigerant type (R-410A on CGAM), nominal tons, voltage class (208/230, 460, or 575 V three-phase).
2. Confirm pad level within 0.25 inch over 10 feet in both directions. Check with a 4 foot machinist's level on the evaporator base rail.
3. Verify 5 feet of clearance on coil intake faces and 8 feet above the condenser fans (Trane CGAM clearance requirements per the IOM).
4. Inspect the brazed plate evaporator inlet and outlet piping for strainer installation upstream of the evaporator. Trane requires a 20 mesh strainer minimum on the chilled water supply.
5. Verify the chilled water differential pressure switch is piped across the evaporator and wired to the Tracer UC400 flow proving input.

Refrigerant circuit verification

CGAM ships with a factory holding charge of dry nitrogen plus a small refrigerant trace. Before opening any valves:

1. Confirm the high side and low side gauges read positive nitrogen pressure on shipment. Zero or vacuum reading means a leak; do not proceed; call Trane warranty.
2. Triple evacuate or single-stage to 500 microns and hold. If the rise exceeds 500 microns in 10 minutes, there is moisture or a leak.
3. Charge with virgin R-410A by weight to the nameplate factory charge value. Do not top off by gauge alone on a scroll system; superheat and subcooling are the field metrics for trim, not for primary charge.
4. Open the liquid line and suction service valves to fully backseat, then crack one quarter turn to enable port access for gauges.

Electrical and control commissioning

1. Verify incoming voltage at the disconnect is within +/- 10 percent of nameplate (per Trane IOM and NEC Section 110.4). A 460 V unit must see 414 to 506 V phase to phase.
2. Measure phase imbalance: maximum 2 percent voltage imbalance, computed as maximum deviation from average divided by average times 100. Imbalance above 2 percent will void scroll compressor warranty under Trane terms.
3. Verify phase rotation with a phase rotation meter. CGAM scroll compressors are not directional inside the compressor, but the condenser fans and the chilled water pump (if interlocked) are direction-dependent. Phase A-B-C must match field labels.
4. Energize the control transformer only; verify 115 V on the Tracer UC400 power input. Do not call for cooling.
5. Verify the chilled water flow switch closes when the pump runs. The Tracer UC400 looks for flow proof within 6 minutes of compressor enable; failure triggers a flow loss diagnostic.

First call to cool sequence

With mechanical, refrigerant, and control checks complete:

1. Set the Tracer UC400 leaving water setpoint to 44 degrees F (factory default).
2. Enable the chilled water pump. Confirm flow switch made.
3. Place the unit in Auto from the Tracer keypad.
4. Watch the staging sequence: lead circuit starts first compressor, anti-recycle timer prevents the second compressor on the same circuit from starting for 5 minutes, then the second circuit's lead compressor stages on if load remains.
5. After 10 minutes of stable run, measure suction superheat (target 8 to 12 F per CGAM TXV setting) and liquid subcooling (target 10 to 15 F at design ambient).
6. Log discharge pressure, suction pressure, ambient dry bulb, entering and leaving chilled water temperatures, and compressor amps on each phase. Trane warranty registration requires these values entered on the startup form.

Lockouts and what they mean

The Tracer UC400 codes you will see most often on first startup:

• Manual Reset Diagnostic: Low Pressure Cutout. Check evaporator flow, strainer cleanliness, refrigerant charge.
• Manual Reset Diagnostic: High Pressure Cutout. Check condenser fan rotation, coil cleanliness, ambient temperature versus capacity table.
• Diagnostic: Loss of Charge. Suction transducer reads below 30 psig at startup. Indicates major refrigerant loss; do not run; investigate.
• Diagnostic: Evaporator Water Flow Loss. Flow switch did not prove within 6 minutes. Verify pump amps, strainer, balancing valve position.

Startup paperwork for warranty

Trane requires the following submitted within 30 days of energization for warranty registration:

• Completed CGAM Startup Test Log (form CG-SVX17H-EN appendix)
• Voltage and phase imbalance measurements
• Pressures and temperatures at design or near-design load
• Refrigerant charge weight (factory plus field add)
• Customer name, address, model and serial numbers
• Authorized startup technician name and Trane TSP ID

References

• Trane CGAM Air-Cooled Scroll Chiller Installation, Operation, and Maintenance Manual CG-SVX17H-EN
• NEC Article 440 Air-Conditioning and Refrigerating Equipment
• ASHRAE Standard 15-2022 Safety Standard for Refrigeration Systems
• AHRI Standard 550/590-2023 Performance Rating of Water-Chilling and Heat Pump Water-Heating Packages