What does Trane chiller diagnostic code 28 mean?

Diagnostic code 28 on Trane chillers typically indicates a low evaporator refrigerant temperature condition approaching freeze protection threshold. Check refrigerant charge level, evaporator fouling factor, and chilled water flow rate. The UC800 controller may lock out the compressor to prevent evaporator freeze damage.

How do I access Trane chiller fault history on a UC800 controller?

On the Trane UC800 touchscreen, navigate to Service > Diagnostics > Diagnostic History. The fault log stores the last 50 fault events with timestamps and operating conditions at the time of trip. Export the log via USB for offline analysis or submission to Trane technical support.

What causes Trane Series R chiller surge?

Compressor surge in Trane Series R centrifugal chillers occurs when the pressure differential across the compressor exceeds the surge envelope, typically due to fouled condenser tubes, reduced chilled water flow, or operation at very light load conditions. The surge control algorithm in the UC800 adjusts guide vane position and hot gas bypass to prevent surge.

How do I perform a refrigerant leak check on a Trane RTAC unit?

Trane RTAC units use R410A. Use an electronic leak detector calibrated for HFCs, checking all Schrader valve caps, service ports, brazed joints, and the sight glass window. Trane recommends the fluorescent dye method for confirming leak location. Always recover refrigerant before brazing repairs and evacuate to below 500 microns.

What is the oil change interval for a Trane screw compressor chiller?

Trane screw compressor chillers using Trane OIL00053 (alkylbenzene) require an oil analysis annually and change every 5 years under normal operating conditions. For POE oil (required with HFC refrigerants), change every 5 years or when oil analysis shows acid or moisture contamination. Always use Trane-approved oil types.

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Common Trane Error Codes

Low evaporator refrigerant temperature — freeze protection active

High condenser refrigerant pressure — check condenser and charge

Low oil pressure fault — check oil separator and pump

Compressor motor winding overtemperature

Loss of flow — chilled or condenser water pump fault

Frequently Asked Questions — Trane

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