TL;DR
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.
What you might see
- evaporator approach temperature above 1 degree C
- condenser approach temperature above 2 degrees C
- chiller running at higher power for same cooling load
- chilled water temperature not meeting setpoint under partial load
Likely causes
Fouled evaporator or condenser tubes reducing the effective heat transfer coefficient
Low refrigerant charge reducing the evaporator wetted tube area
Reduced water flow on either the chilled water or condenser water side
Improperly balanced refrigerant distribution inside the evaporator shell
Required tools
- Chiller controls access (Trane Tracer panel)
- Calibrated thermometers for water side temperatures
- Tube brush cleaning kit (for condenser or evaporator cleaning)
Safety first
- Evaporator tube access requires isolating and draining the chilled water circuit. Confirm isolation before opening the water box.
- Refrigerant charge verification requires EPA Section 608 certification.
Procedure
- 1
Calculate the evaporator approach temperature: chilled water leaving temperature minus saturated evaporating temperature. Record the value.[1]
- 2
Calculate the condenser approach temperature: saturated condensing temperature minus condenser leaving water temperature. Record the value.[1]
- 3
Compare both values to the baseline from the last tube cleaning. An increase of more than 0.5 degrees C in either is significant.
- 4
Verify chilled water flow rate at the evaporator and condenser water flow at the condenser. Compare to design flow from the original commissioning report.
- 5
If condenser approach is elevated, schedule a condenser tube cleaning (see the high-discharge-pressure procedure on this machine).
- 6
If evaporator approach is elevated and flow is normal, a Trane-certified technician should check refrigerant charge and evaporator liquid level.
- 7
After tube cleaning or refrigerant correction, record the new baseline approach temperatures for future trending.
Sources
Trane CenTraVac Chiller Operation and Maintenance Manual, Trane (Trane Technologies)
Trane CenTraVac Operation and Maintenance Manual, approach temperature analysis and heat exchanger maintenance (general)
View source
More guides for Trane CenTraVac
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.
How to fix low cooling output on a Trane CenTraVac chiller
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.
Stop fixing the same fault twice.
Dovient turns guides like this into your team's shared playbook, with AI that catches recurring issues before they break the line.