Canon 2000 Select Blower Range, Principles of Infiltrometer Air Flow Measurement, Changing Ranges

Select Blower Range

Principles of Infiltrometer Air Flow Measurement

The Infiltrometer can accurately measure airflow between 18 CFM and 6500 CFM. However, in order to measure accurately over this wide range, the range must be changed as described in the following section.

The Infiltrometer fan blade pushes air out the back of the fan creating a negative pressure in front of the blades. This negative pressure pulls air through the fan's rounded (venturi) shaped inlet. More negative pressure, more flow. The Infiltrometer has been calibrated so for each size of inlet opening and for each negative pressure (Flow Pressure) the flow rate in cubic feet per minute (CFM) is known. As flow decreases the Flow Pressure decreases eventually to the point that it becomes too low to read accurately.

By reducing the size of the inlet with the restrictor plate a given amount of air is forced to enter the blower at a higher velocity, resulting in a much higher flow pressure. (The fan speed must be increased in order to pull the same quantity of air through the blower with the restrictor plate in place.)

Therefore, as the flow rate requirement decreases, such as in tighter buildings, the size of the blower inlet must decrease to maintain a high and accurately readable Flow Pressure. Each inlet size has a pre-established configuration or range. Ranges are somewhat analogous to gears in a standard transmission car. The slower you go the lower the gear.

Changing Ranges

The Retrotec 2000 Series Infiltrometer blower has 7 flow ranges for the greatest possible accuracy and versatility.

Range 22 (wide open with no restrictor plate installed) is the most powerful and most commonly used range. It is used to test buildings with ELA's greater than approximately two square feet.

To use range 22, remove all the restrictor plates.

Range A (1st restrictor ring attached) is the next most commonly used range. It is used to test House/Rooms with ELA's between approximately one and three square feet.

Range B (2nd restrictor ring attached) is used to test House/Rooms with ELA's less than one square foot.

Ranges C8 requires the installation of the plate with 8 holes open, on top of the motor. Ranges C4 down to C1 require plugging some of the holes. Put plugs in the exact positions as shown - others will produce erroneous results. These very restrictive ranges are needed when testing very small rooms.

Each plug must be gently worked into the hole, but be careful you do not push the Panels right out of the doorway. (If the blower is ever turned around for reverse measurement, ensure none of the plugs have fallen out by peeking through the screen.)

2000 Fire Door-Fan Manual updated 2002-05-28 Page 20 of 58