Trane RTHD Fault Code 390B
Trane RTHD Fault Code 390B is a warning alarm indicating: Communication Lost - Main CCN to Starter Circuit B. The most common causes include CCN cable to starter B damaged. Estimated repair time: 1-3 hours (requires board replacement, configuration, and commissioning). This alarm requires immediate attention by a certified HVAC technician.
Alarm Description
Communication Lost - Main CCN to Starter Circuit B
Brand: Trane | Model: RTHD (Helical Rotary Chiller) | Code: 390B | Severity: Warning
Observable Symptoms
- Controller display shows communication error or blank screen
- BAS/EMS system shows chiller as offline or in alarm state
What to Check First
Before diving into detailed diagnostics, start with this quick first check:
Probable Causes
- CCN cable to starter B damaged
- Starter B board power failure
- Address conflict on CCN bus
Recommended Inspection Steps
- Check CCN cable to starter B
- Verify starter B power
- Check CCN address settings
- Replace starter B communication board
Required Tools & Equipment
- Safety PPE (gloves, safety glasses, face shield)
- Wire tracing and continuity tester
Estimated Repair Time
1-3 hours (requires board replacement, configuration, and commissioning)
When to Call a Professional
- If the fault persists after completing all recommended inspection steps
- If you observe unusual noises, vibrations, or oil leaks from the compressor
- If refrigerant charge levels are outside OEM specifications and EPA-certified recovery is needed
- If electrical measurements show voltage imbalance greater than 2% between phases
- If the fault recurs immediately after reset, indicating an unresolved safety condition
- Contact an authorized Trane service representative for warranty-covered repairs
Related Fault Codes
Other Trane RTHD codes that may be related:
OEM Service Manual Reference
OEM Reference: Trane RTHD Water-Cooled Helical Rotary Chiller Service Manual (SVR-SVN002-EN). Trane CH530 Controls manual also required.
Frequently Asked Questions
What does Trane RTHD fault code 390B mean?
Fault code 390B on a Trane RTHD chiller indicates: Communication Lost - Main CCN to Starter Circuit B. This is a warning alarm that requires diagnostic attention.
What causes Trane RTHD alarm code 390B?
Common causes include: CCN cable to starter B damaged; Starter B board power failure; Address conflict on CCN bus
How do I fix Trane RTHD error code 390B?
Follow the recommended inspection steps below. Start with the quick check, then proceed through each step. If the fault persists after all steps, contact an authorized Trane service representative.