HVACopedia

All brands · Furnace troubleshooting

High blower-door ACH50 (>3)

What is going on

Possible causes and checks for: high blower-door ach50 (>3).

Likely causes

  • Leaky envelope

Check in this order

  1. Locate with smoke/thermal imaging at −50 Pa
  2. Seal

More furnace 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.