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2B. DETERMINE FRESH AIR INTAKE
Flow Hood Anemometer Method
1. Use a fl ow hood or handheld rotary blade anemometer. Follow the instruments recommend
procedures for obtaining an accurate measurement.
2. During a Heating and Cooling cycle take a measurement and record the CFM volume through the
outdoor fresh air intake.
Static Pressure Method
1. Locate where the fresh air intake and return air duct connect.
2. Use a monometer following the instruments recommended procedure for obtaining an accurate
static pressure measurement. Take measurements in the fresh air intake duct approximately one
foot from the return air and fresh air intake connection.
3. Record the average static pressure measurement for a heating and cooling cycle.
4. Determine the fresh air intake internal round duct size and type. If square or rectangular duct
convert free area to the nearest round duct size.
5. Determine the fresh air intake systems total equivalent feet.
How many elbows, reducers and straight pipe used in construction of the fresh air intake duct.
For additional details see section 10.
6. Using table 3
a)
Select your damper and air intake hood size.
b)
Moving to the right select your systems total equivalent feet
c)
From the top locate your systems Cooling or Heating cycle measured negative static
pressure.
d)
Select your systems duct type Smooth or Flex
e)
Drop down your selected duct type column to where it intersects with your
predetermined equivalent feet row.
f)
Your estimated Cooling CFM has been determined. Record and save.
g)
Repeat the process if Heating cycle static pressure is different.
Note: If Cooling and Heating cycle static pressure is the same continue.
P/N 780100700 07/18 Rev F
Heat
Cool
Page 8 of 36
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