Lennox TCS Fault Code E21
Lennox TCS Fault Code E21 is a critical safety alarm indicating: Compressor 2 oil pressure low. The most common causes include Oil pump 2 failure. Estimated repair time: 1-2 hours (requires oil addition or oil change, filter replacement). This alarm requires immediate attention by a certified HVAC technician.
Alarm Description
Compressor 2 oil pressure low
Brand: Lennox | Model: TCS (Water-Cooled Screw Chiller) | Code: E21 | Severity: Critical
Observable Symptoms
- Oil sight glass shows low level or empty
- Compressor may make unusual noise from lack of lubrication
- Oil pressure differential alarm may also be active
What to Check First
Before diving into detailed diagnostics, start with this quick first check:
Probable Causes
- Oil pump 2 failure
- Oil filter 2 clogged
- Low oil in compressor 2
Recommended Inspection Steps
- Check compressor 2 oil level
- Replace oil filter 2
- Measure oil pump 2 pressure
Required Tools & Equipment
- Oil level sight glass inspection tool
- Safety PPE (gloves, safety glasses, face shield)
Estimated Repair Time
1-2 hours (requires oil addition or oil change, filter replacement)
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 Lennox service representative for warranty-covered repairs
Related Fault Codes
Other Lennox TCS codes that may be related:
OEM Service Manual Reference
OEM Reference: Lennox TCS Water-Cooled Screw Chiller Service Manual. Available through Lennox Commercial technical support.
Frequently Asked Questions
What does Lennox TCS fault code E21 mean?
Fault code E21 on a Lennox TCS chiller indicates: Compressor 2 oil pressure low. This is a critical safety alarm that requires diagnostic attention.
What causes Lennox TCS alarm code E21?
Common causes include: Oil pump 2 failure; Oil filter 2 clogged; Low oil in compressor 2
How do I fix Lennox TCS error code E21?
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 Lennox service representative.