What Are Range Rings & Plates?
Range rings (or plates) are restrictive attachments placed on the blower-door fan inlet. They narrow the airflow, increasing fan pressure, which improves measurement precisionāespecially at lower flow rates where the gauge needs sufficient pressure differential to provide reliable data.
Why Range Selection Matters
Measurement Resolution
- Too little restriction yields low fan pressure, which may fall below the gaugeās readable range.
Fan Efficiency & Cooling
- Higher fan pressure enables faster fan speeds, helping prevent the motor from overheating.
Test Accuracy Across Multiple Points
- Using a restrictive configuration throughout the test avoids mid-course adjustments, ensuring continuity and consistency
How to Select the Correct Range
Hereās Retrotecās recommended process:
Install the most restrictive range you anticipate needing (e.g., small-hole ring).
Secure the range ring, making sure alignment pins are properly seated.
Adjust fan speed until you reach your target test pressure (e.g., 50āÆPa).
If the gauge displays āā āā, flow is too lowāadd more restriction by switching to a smaller-hole ring or plate and retest.
Monitor fan pressure on the gauge (PrB). The ideal fan pressure is at least twice your test pressure (e.g., ā„āÆ100āÆPa for a 50āÆPa test).
Proceed with the blowerādoor test on that range ring for both single- and multiple-point tests.
Quick Reference Table
| Test Pressure Target | Min. Fan Pressure Needed | Choose Range |
|---|---|---|
| 50āÆPa | ā„āÆ100āÆPa | Restrictive ring/plate |
| 75āÆPa | ā„āÆ150āÆPa | Smaller-hole ring if needed |
| Multi-point Tests | Maintain ā„2Ć at all points | Full-range coverage |
Bottom Line
Using the right range ring ensures:
Reliable readings by keeping fan pressure within gauge specs
Operational safety and fan cooling efficiency
Data consistencyāno need to switch ranges mid-test
