HVACopediaAll brands · General troubleshooting
Negative pressure / drafts / spillage
What is going on
Possible causes and checks for: negative pressure / drafts / spillage.
Likely causes
- Combustion appliance drawing house air
- Add makeup air unit (return-duct damper type or mechanical-room type)
More general guides
Take it to the job
All guides, error codes and tips work offline in the HVACopedia 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.