Lennox Central Unit Fault Diagnosis: Fast and Methodical Intervention
At AirGreen , we were called out to Blainville for a complete breakdown of a Lennox central heat pump installed in a single-family home. The customer reported no heating for several days despite a working thermostat and a flashing indicator light on the outdoor unit.
Initial inspection: reading error codes and electrical measurements
Upon arrival, our certified HVAC technicians conducted a systematic check of the outdoor condenser . The first clues—a quiet compressor and a stationary fan —pointed to an electrical or safety issue with the circuit. After opening the control panel, the E233 – High Pressure Lockout code appeared on the Lennox SmartHub board.
We then undertook a measurement of the supply voltage (240V) and a check of the starting relays, while observing an abnormal static pressure in the refrigeration circuit, a potential sign of excess refrigerant or a blockage of the flow .
In-depth diagnosis: refrigerant circuit overload
Using an electronic manifold and a calibrated charge balance , we confirmed that the circuit contained nearly 25% excess gas . This overload was the direct cause of the high pressure triggering and the compressor being shut down. The probable cause: a recharge error during a previous intervention .
Repair steps: AirGreen expertise in action
1. Securing and recovering the refrigerant
Our technicians carefully recovered the R410A refrigerant using an approved cylinder and a Titan Pro station, seen here in operation. This step prevented any improper degassing and preserved the environmental integrity of the refrigerant.
2. Rebalancing the circuit
After recovery, the system was evacuated to a full vacuum at -30 inHg for 40 minutes to remove any moisture or air. We then recharged the gas precisely to Lennox specifications—5.4 lb of R410A, measured to the nearest gram, in liquid mode through the high-pressure side.
3. Checking operation and pressures
Once the charge was complete, the measurements showed:
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Suction pressure : 118 psi
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Discharge pressure : 385 psi
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Superheat : 9.1°F
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Subcooling : 8.5°F
Values perfectly in line with Lennox performance standards for a day at 22°C ambient.
4. Final check of the compressor and fan
After restarting, the Lennox scroll compressor resumed stable and quiet operation. The condenser fan activated without vibration or speed oscillation, confirming that the control module (inverter) had not been damaged by the initial surge.
Results obtained: comfort restored and reliability regained
The client immediately noticed a return of even heating throughout the house, with a constant flow of hot air and normalized electricity consumption . After several test cycles, no errors were detected. We also reprogrammed the SmartHub system to ensure continuous pressure monitoring.
AirGreen Lessons and Advice
This intervention in Blainville illustrates a classic case of refrigerant charging error , often committed during maintenance not carried out by certified technicians. Too much or too little refrigerant can cause:
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a high pressure safety device ,
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a drop in energy efficiency ,
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or even premature wear of the compressor .
At AirGreen , we always favor precise and safe methods:
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Electronic scales calibrated for each refill,
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Superheat/subcooling analysis before validation,
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Leakage control with electronic detector to prevent micro-leaks.
Thanks to this rigorous approach, the Lennox system in Blainville now operates at full efficiency , guaranteeing comfort and durability to the customer, in all seasons.