Field Controls FAPV180-AC Manual page 12

• • Pitot Tube Measurement using a Manometer with fl ow measurement capability (HVAC air pressure/fl ow Pitot Tube Measurement using a Manometer with fl ow measurement capability (HVAC air pressure/fl ow
measurement instrument), see Figure 6: measurement instrument), see Figure 6:
1. Turn on the manometer and perform the "zero" procedure in an area without air currents.
2. Set the manometer to measure air fl ow in a round 6" duct and connect the pitot tube ports with
rubber tubing. The center port on the pitot tube should connect to the port marked + or POS on
the manometer, while the side port on the manometer should connect to the port marked NEG or –.
3. Remove the test port plug from the inlet collar of the FAPV fan unit, insert the pitot tube such
that the tip of the tube is in the center of the inlet collar and facing upstream (away from the FAPV
fan unit, towards the intake hood), allow the reading to become steady and take an airfl ow reading.
• • Inlet Duct Static Pressure Measurement using a simple Manometer (air pressure gauge), see note on Figure 6. Inlet Duct Static Pressure Measurement using a simple Manometer (air pressure gauge), see note on Figure 6.
1. Measure the length of duct that is used. Add 12 feet for every 90° bend or elbow; this will be the
approximate "equivalent length" of the duct system for use in determining the approximate air
fl ow rate. NOTE: the fl ow rate table to be used includes the eff ects of typical intake air hoods in
the estimates given on the table; do not add any extra feet to the equivalent length for the intake
hood.
2. Turn off all exhaust fans, central vacuum systems, fi replaces etc. and open doors or windows from
the FAPV area to the outdoors if possible.
3. Ensure that there are no air currents in the area where measurements are to be taken.
4. Make sure the speed control knob is set to the MAX position.
5. Turn on the manometer, set it to read in in inches of water ("wc, or inH2O for example) and perform
the "zero" procedure in an area without air currents.
6. Connect a rubber air pressure tube to the manometer port marked NEG or –.
7. Remove the test port plug from the inlet collar of the FAPV fan unit and insert the end of the
pressure tube very slightly into the port and use tape to temporarily seal the tube to the port. Allow
the reading to become steady and take a pressure reading (ignore a minus sign on the reading if
present).
8. Find the desired intake duct static pressure on page 14 for the type and length of duct used, fi nd
which horizontal row on the table corresponds to the intake hood size, duct size and length for the
installation. For duct lengths more than 9 feet longer than a row's duct length, use the row for the
next longest length. On that row, fi nd the nearest value to the desired ventilation airfl ow rate (cfm),
and at the top of the vertical column that the fl ow rate is found, fi nd the approximate static air
pressure corresponding to that fl owrate.
P/N 780104900 Rev A 09/20
Figure 6, AIR FLOW TUBE MEASUREMENT METHODS
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