Retrotec DucTester 200 Series Residential Applications - Manual (Page 56)

Page 56 of 91
©Retrotec Inc. 2015
Attach the blue Tube to the connector on the Flow Hood. Connect the other end to the “Input A” port
(blue) on the gauge. The “Ref A” (red) port on the gauge should be left open.
Connect the green and yellow tubing to the “Input B” (green) and “Ref B” (yellow) ports on the gauge
respectively. Connect the other ends to the same color ports on the DucTester.
Adjust the [Set Speed] until “PrA” reads a pressure of 0 Pa. Record the flow in CFM. To have the
DucTester automatically acquire and maintain a 0 pressure, press [Set Pressure] [0] and the gauge will
cause the DucTester to increase in speed to eliminate whatever pressure it sees at the time that the
keys are pressed.
Ensure the pressure that is to be set to 0 actually exists before the keys are pressed because it uses the
direction of the pressure to set the direction of control. This means that the will fan speed up to
eliminate the pressure it first sees regardless of sign. Make sure the “@ Pressure” feature is turned off,
otherwise erroneous results will occur due to the result being divided by whatever tiny pressure occurs
above or below zero.
9.4 Measure with a DucTester on the air handler cabinet
Ensure the “n” value on the gauge is set to 0.5. A unique feature on the Retrotec gauge will allow the
gauge to accurately calculate the air handler flow rate even if the DucTester is not capable of achieving
exactly the same flow rate as the air handler is putting out.
On the DM-2 gauge, press the [Setup] key and scroll to “N=” and set it to 0.5.
Measure the supply plenum pressure using the Static Pressure Probe supplied with each DucTester. Put
the end of the blue tube with the probe into the supply plenum, connect the other end of the blue tube
to the “Input A” (blue) port and read the pressure from “PrA” on the gauge.
Attach the DucTester to the cabinet using cardboard and tape so it is blowing into the air handler on the
Open range. Set Pressure to the previously measured value. Press
[Set Pressure] and enter the
previously measured supply plenum pressure. Press the [@ Pressure] key until the supply plenum
pressure appears as “CFM@”. Read the “CFM@” result on the gauge.
For example, if the pressure in the supply plenum is 70 Pa, Press [Set Pressure] , [70] , [Enter] to get the
DucTester to recreate the original pressure in the plenum. Press the [@ Pressure] key until “CFM @ 70
Pa” appears on the display. The CFM result displayed will be corrected for what the airflow will be
during normal operation (the supply pressure in the plenum measured at the start of the test).
If “TOO LOW” or “----“appears the pressure in the plenum is too high to get an accurate reading. Repeat
the procedure but move the Static Pressure Probe to measure the pressure farther away from the air
handler.
9.5 Measure with a gauge and a flow grid
A unique Retrotec feature allows the gauge to be used with flow grids from other manufacturers.
Press the [Setup] key and scroll to “N=” and set it to 0.5.
Set the gauge to the flow grid using the [Setup] key. Use the “Mode Setup” menu as necessary to
enable the flow grid as a choice of Device on the gauge.
Measure the supply plenum pressure using the Static Pressure Probe supplied with each DucTester. Put
the end of the blue tube with the probe into the supply plenum, connect the other end of the blue tube
to the “Input A” (blue) port and read the pressure from “PrA” on the gauge.
Install the flow grid into the filter slot per manufacturer instructions, which includes connecting the
green and yellow tubes to the gauge. Press
[Set Pressure] and enter the just measured supply plenum