HVACopedia

All brands · General troubleshooting

Low airflow / rooms starved at end of runs

What is going on

Possible causes and checks for: low airflow / rooms starved at end of runs.

Likely causes

  • Leaky joints
  • Undersized or long runs, too many elbows
  • Duct in plenum end
  • Clogged filter
  • High ESP

Check in this order

  1. Seal with mastic
  2. Booster fan
  3. Duct test cfm25 ≤4/100 ft²
  4. Filter ΔP ≤25% of fan ΔP
  5. Total pressure drop ≤0.5 in. WC

More general guides

Related

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: General HVAC service practice — verify per model. 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.