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RDS leak-detected mode and start-up test - Lennox EL16KC1

What is going on

The refrigerant detection system (RDS) blower control board shuts down the compressor (and gas burners) and runs the blower when it detects R-454B; its LED flashes blue.

Likely causes

  • Real refrigerant leak near the indoor coil
  • Test button pressed (simulated leak)
  • Sensor or RDS board problem

Check in this order

  1. Warning: R-454B is mildly flammable (A2L). Remove ignition sources and ventilate before working on a suspected leak.
  2. The unit must not run until the RDS is verified working.
  3. After power-up the RDS board runs a 5-minute purge sequence before normal operation.
  4. Cooling test call for cooling, press Test on the RDS board - LED flashes blue, blower starts, outdoor compressor stops. Press Test again to end.
  5. Heating test call for heat, press Test - LED flashes blue, blower starts, gas burners and compressor stop. Press Test again to end.
  6. If a second sensor is required (extra unsleeved joints with a furnace), mount it 9 in. above floor / within 9 in. of the front per the application and enable the second sensor input on the RDS control.
  7. Leak-check the whole system to 5 grams per year sensitivity after repairs.

Applies to: Lennox EL16KC1 (Elite) R-454B air conditioners, sizes -018 to -060

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Source: Lennox EL16KC1 Unit Information Corp. 100121 (01-2025), Line Set Joints / Secondary Sensor pp.14-15, Leak Test p.22, Electrical p.24, Start-Up Test Procedure p.36. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.