HVACopedia

Lennox · Air conditioner troubleshooting

Low cooling capacity - check airflow and charge - Lennox EL16KC1

What is going on

Unit runs but does not cool well; airflow and charge must both be checked and adjusted together.

Likely causes

  • Indoor airflow too low or too high
  • Wrong charge
  • Dirty filters or coils
  • Line set length not accounted for in charge

Check in this order

  1. Make sure filters and indoor/outdoor coils are clean before testing.
  2. Measure entering air dry bulb and wet bulb at the indoor coil and find the target Delta-T in the Delta-T table.
  3. Measure leaving air dry bulb; the drop across the coil should be within +/-3°F of the target. Drop too high = increase fan speed; too low = decrease fan speed.
  4. Compare subcooling (saturated LIQUID temp less liquid line temp) and approach to the charging table for this unit size, within +/-1°F.
  5. Factory charge is for a 30 ft line set: add 3 oz per 5 ft over 30 ft (3/8 in. liquid line), remove the same under 30 ft.
  6. Charge with liquid only (R-454B is a blend) and mark the total charge on the nameplate.
  7. Repeat airflow and charge checks until both are right.

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

More air conditioner guides

Related

Lennox error codes · Lennox parts · Lennox tips · Calculators and reference tables

Take it to the job

All guides, error codes and tips work offline in the HVACopedia app.

Open the app

Source: Lennox EL16KC1 Unit Information Corp. 100121 (01-2025), Figure 19 p.33, Charging Procedures p.37. 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.