How Blower Door Testing Works

How Our Calibrated Fan’s create flow and Fan Pressure

When the fan is turned on, air starts moving through the fan housing. In order for the air to be pulled through the holes on the inlet side, there must be suction. The rotating fan blade creates a suction pressure (which is also called Fan Pressure) between the inlet opening and the fan blade.

Range Rings and Plates are installed on the inlet side of the fan housing to artificially restrict flow, control the amount of air going through the fan, and thus control the Fan Pressure.

The purpose of controlling flow through the fan is for measuring different leakage ranges.

Restricting air flow is important because it enables you to measure smaller or larger holes.

Eg, Measuring how much water can fit in a cup with a swimming pool is impossible.

By measuring the Fan Pressure developed across the fan housing, and knowing the size of the hole(s) in the installed Range, we can calculate the volume of air moving through the fan. The area which is being pressurised will exert pressure at the gauge green port which will be picked up and included as part of the measured pressure difference. Our self-referencing fans avoid the need for adjusting Fan Pressure measurements by measuring the pressure difference at the fan inlet directly with both the green and yellow tubes connected to either side of the fan inlet on the fan.  With our self-referencing fans both yellow and green tubes are connected between the fan and the gauge, and there is no compensation for the room pressure.

The gauges,each with a fan all talk to a computer via IP/Wifi, and the computer can capture data from up to 24 fans, for measuring leakage in extremely large buildings.  Each one of our fans can move up to 14000m3/h @ 50Pa, when completely unrestricted.