Lennox SCA Fault Code E21
Lennox SCA Fault Code E21 is a warning alarm indicating: Discharge temperature high 2. The most common causes include Compression ratio too high on circuit 2. Estimated repair time: 45-90 minutes. This alarm requires immediate attention by a certified HVAC technician.
Alarm Description
Discharge temperature high 2
Brand: Lennox | Model: SCA (Air-Cooled Scroll Chiller) | Code: E21 | Severity: Warning
Observable Symptoms
- Discharge temperature gauge reads above 250F (121C)
- Discharge line may be hot enough to cause burns on contact
- Compressor oil may appear dark or burnt
What to Check First
Before diving into detailed diagnostics, start with this quick first check:
Probable Causes
- Compression ratio too high on circuit 2
- Oil level low in compressor 2
- Condenser 2 not rejecting heat
Recommended Inspection Steps
- Check discharge temp on circuit 2
- Verify oil level in compressor 2
- Inspect condenser 2 operation
Required Tools & Equipment
- Infrared thermometer or calibrated temperature probe
- Oil level sight glass inspection tool
- PT chart for refrigerant type
- Safety PPE (gloves, safety glasses, face shield)
Estimated Repair Time
45-90 minutes
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 SCA codes that may be related:
OEM Service Manual Reference
OEM Reference: Lennox SCA Air-Cooled Scroll Chiller Service Manual. Available through Lennox Commercial technical support.
Frequently Asked Questions
What does Lennox SCA fault code E21 mean?
Fault code E21 on a Lennox SCA chiller indicates: Discharge temperature high 2. This is a warning alarm that requires diagnostic attention.
What causes Lennox SCA alarm code E21?
Common causes include: Compression ratio too high on circuit 2; Oil level low in compressor 2; Condenser 2 not rejecting heat
How do I fix Lennox SCA 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.