TL;DR
Low cooling output is most often a low refrigerant charge or fouled condenser tubes. Check the approach temperature across the condenser, read the operating log for refrigerant suction and discharge pressures, and contact a licensed refrigerant technician if charge is suspect.
What you might see
- leaving chilled water temperature above setpoint
- compressor running at full load without meeting demand
- suction pressure lower than normal
- refrigerant sight glass showing bubbles
Likely causes
Low refrigerant charge from a system leak, reducing heat transfer capacity
Fouled condenser tubes increasing condensing temperature and limiting compressor capacity
Excessive condenser water temperature from a poorly performing cooling tower
Inlet guide vane or variable speed drive not opening fully to meet load
Required tools
- Chiller controls access (Trane Tracer panel)
- Calibrated thermocouple or RTD for water temperatures
- Refrigerant manifold gauge set (licensed technician only)
- Tube brush cleaning kit (for condenser tube cleaning)
Safety first
- Refrigerant handling on CenTraVac chillers requires EPA Section 608 certification. Do not vent refrigerant to atmosphere.
- Low-pressure refrigerant systems can have sub-atmospheric evaporator pressure. Air ingress through a leak creates non-condensable gas contamination and a moisture hazard.
Procedure
- 1
Pull the chiller operating log from the Tracer controls panel and compare current suction pressure, discharge pressure, and condenser leaving water temperature to the last clean baseline.[1]
- 2
Calculate the condenser approach temperature: condenser leaving water temperature minus saturated condensing temperature. An approach above 2 degrees C indicates tube fouling.[1]
- 3
Verify the cooling tower is delivering condenser water at design entering temperature. A warm condenser water supply reduces chiller capacity independent of refrigerant charge.
- 4
Check the inlet guide vane position and response. Command a full-open from the controls panel and observe whether the vanes move to 100%.
- 5
If suction pressure is consistently below the normal operating band and sight glass shows bubbles, the system likely has a refrigerant leak. Do not attempt to add refrigerant without first locating the leak.
Warning: R-11, R-113, and low-pressure refrigerants used in CenTraVac chillers are above atmospheric pressure in the evaporator under some conditions. Work requires licensed refrigerant handling certification. - 6
Schedule a condenser tube cleaning if the approach temperature is elevated. Use a tube brush kit and hydraulic cleaning rig.
- 7
If a refrigerant leak is confirmed, contact a Trane-certified service technician for leak repair and recharge under vacuum.
Sources
Trane CenTraVac Chiller Operation and Maintenance Manual, Trane (Trane Technologies)
Trane CenTraVac Operation and Maintenance Manual, refrigerant circuit troubleshooting and approach temperature analysis (general)
View source
More guides for Trane CenTraVac
How to fix high approach temperature on a Trane CenTraVac chiller
A rising approach temperature means heat transfer is degrading. On the condenser side this is almost always tube fouling. On the evaporator side it can also be low refrigerant charge. Calculate both approach temperatures from the operating log and address the affected side.
How to stop compressor short cycling on a Trane CenTraVac chiller
Short cycling at low load means the chiller is hunting around its setpoint or the system load is below the minimum stable capacity. Widen the chilled water setpoint deadband and check the inlet guide vane minimum stop.
How to diagnose frequent fault alarms on a Trane CenTraVac chiller
Multiple spurious alarms usually point to a single faulty sensor or a wiring issue sending bad data to the controls board. Cross-check each alarmed sensor reading against an independent instrument before replacing the controls board.
How to fix high discharge pressure on a Trane CenTraVac chiller
High discharge pressure is almost always fouled condenser tubes or non-condensable gas in the refrigerant circuit. Calculate approach temperature first, then clean tubes or purge non-condensables as indicated.
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