Centrifugal Chillers Critical Interlock

Carrier 19XR Alarm 125: Motor Bearing High Temperature — Hermetic Compressor

Published: 2026-06-01

🚨 Critical Diagnostic Alert

Alarm 125 on the Carrier 19XR hermetic centrifugal chiller monitors the motor bearing temperatures via embedded RTD sensors. The PIC III controller triggers this alarm when either the drive-end or non-drive-end bearing temperature exceeds 195°F for more than 30 seconds. This is a bearing protection alarm — the chiller trips to prevent bearing seizure which, in a hermetic compressor, would require a factory rebuild ($20,000-35,000).

The 19XR's hermetic design means the motor and bearings are cooled by the same refrigerant that flows through the compressor. Any reduction in refrigerant mass flow — whether from low charge, a restricted filter drier, or a failing motor cooling TXV — simultaneously reduces bearing cooling. This makes bearing temperature trending one of the most valuable predictive maintenance data points on the 19XR.

🔍 Symptoms Checklist

⚠️ Motor bearing RTD reads above 195°F
⚠️ Unusual high-pitched whine from compressor motor end
⚠️ Vibration analysis shows elevated high-frequency component at bearing pass frequency
⚠️ Alarm triggers after 6-8 hours of continuous operation — not at startup

🛠️ OEM Replacement Parts

Part Name	OEM Part Number	Est. Price
Motor Bearing RTD Sensor Assembly	`HK06RTD001`	$480
Motor Cooling Liquid Line Filter Drier	`HK06FLT001`	$95
Motor Bearing Set (Journal + Thrust, 19XR)	`HK06BRG-KIT`	$6,800

📋 Interactive Diagnostic Procedure

Click each step to expand detailed diagnostic instructions. Follow in sequence — each step builds on the previous one.

1 Verify Motor Cooling System

The 19XR uses liquid refrigerant injection to cool the hermetic motor. A restricted motor cooling liquid line filter drier starves the motor of cooling, causing bearing temperatures to rise. Measure the temperature drop across the filter drier — more than 3°F indicates restriction. Replace the filter drier and inspect the motor cooling TXV for proper operation. The TXV should maintain 15-20°F motor winding superheat at all load conditions.

2 Check Bearing Vibration Spectrum

Connect a vibration analyzer to the compressor motor housing at the bearing locations. A healthy bearing shows broadband noise below 0.1 in/sec RMS. Elevated amplitude at the bearing pass frequency (BPFO for outer race, BPFI for inner race, BSF for ball spin) indicates specific bearing component wear. Outer race defects typically produce a 'washboard' pattern at 3-5× shaft RPM. Inner race defects modulate at shaft RPM. Trend the vibration readings — a 2× increase over 6 months indicates progressive wear requiring planned bearing replacement.

3 Inspect Refrigerant Charge & Oil Condition

Low refrigerant charge reduces the mass flow available for motor cooling, causing the motor to run hotter and conduct more heat to the bearings. Additionally, acid formation in the oil (indicated by a high Total Acid Number >0.5) attacks bearing surfaces and increases friction. Take an oil sample — if TAN exceeds 0.5, perform a complete oil change and install an acid-removal filter core before restarting.

🔗 Related Error Codes — Centrifugal Chillers

Other diagnostic guides in the same equipment category. Common failure patterns often share root causes — cross-referencing speeds up diagnosis.

Centrifugal Chillers Critical Interlock

⚡ Fault-Induced Energy Waste Estimator

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References & Industry Standards

ASHRAE 15 — Safety Standard for Refrigeration Systems
ASHRAE 34 — Refrigerant Designation & Safety Classification
AHRI 550/590 — Water-Chilling & Heat Pump Packages
SMACNA — HVAC Duct Construction Standards
Manufacturer Service Manuals — Carrier, Trane, York, Daikin, Lennox

Carrier 19XR Alarm 125: Motor Bearing High Temperature — Hermetic Compressor

🔍 Symptoms Checklist

🛠️ OEM Replacement Parts

📋 Interactive Diagnostic Procedure

🔗 Related Error Codes — Centrifugal Chillers

Carrier 19DV Chiller Alarm 104: Centrifugal Compressor Surge Diagnosis

York YK Chiller Alarm: Compressor Surge & High Lift Protection

Daikin WMC Chiller Alarm E3: Motor Overcurrent & VFD Fault

Trane CVHE Chiller Alarm 8D: Low Evaporator Refrigerant Temperature

Carrier 19DV Alarm 102: Low Oil Pressure — Compressor Lubrication Failure

York YK Chiller Alarm: High Oil Temperature — Oil Cooler Performance

Trane CVHE Alarm 8A: High Condenser Pressure — Heat Rejection Failure

Daikin WMC Alarm E7: Magnetic Bearing Controller Fault — Levitation Loss

⚡ Fault-Induced Energy Waste Estimator

References & Industry Standards