Why your flow may read “too low” on your gauge and what to do about it.
What “Too Low” Indicates
This reading appears when the gauge thinks the airflow is below the minimum threshold needed for a valid reading. In short, the fan isn’t providing enough pressure or flow for the selected gauge range and test setup to work properly.
Common Causes and Fixes
Wrong Gauge Range Selected
If the range is set too narrow, it may not capture higher flows.
If too wide, minor flow won’t register.
Fix: Select a range that centers around your target pressure (e.g., 50 Pa for blower-door). Switch to the next adjacent range if needed.
Fan Speed Too Low
If the fan isn’t running fast enough, it can’t generate proper flow.
Fix: Ensure the fan is powered and running at adequate speed; if it’s slow, increase until flow registers.
Set-up or Plumbing Issues
Tubing leaks, kinks, or the gauge/fan configuration could restrict flow.
Fix: Inspect tubes for damage; ensure correct connections from fan to gauge; reroute or replace if needed.
Loose Fan Installation or Bypasses
Air leaks around the fan or door panel can reduce backpressure and flow.
Fix: Tighten fan connections and panel seals so all airflow goes through the fan/blower only.
Step-by-Step Checklist
- Check the flow range on the gauge; adjust to align with test pressure.
- Confirm the fan is operating and responding to input.
- Inspect all tubing and fittings for leaks or blockages.
- Ensure the blower panel is sealed correctly to prevent bypass airflow.
Why it Matters
Accurate airflow readings are essential for airtightness calculations, HVAC testing, and code compliance. A “too low” flow warning means your data is invalid—fix it early to avoid wasted time or skewed results.
