Lo" Displayed On Channel B; Changing The Air Flow Units; Changing The Time Averaging Period; Using The Baseline Pressure Feature In Pressure/Flow Mode - TEC DG-700 Operating Instructions Manual

3.4 "LO" Displayed on Channel B

Whenever "LO" appears on Channel B in the PR/ FL mode, the pressure signal from the test device is too low to
provide a reliable air flow reading. The message "LO" appears on the Channel B display under the following two
conditions:

"LO" is continuously displayed on Channel B when there is negligible air flow through the test device.

"LO" alternates with a flow reading when the air flow reading through the device is unreliable (i.e. you are
trying to measure a flow outside of the calibrated range of the test device in its current configuration). If
possible, the user should change the test device configuration to match the flow rate being measured (e.g. install
a flow ring or a smaller flow ring).

3.5 Changing the Air Flow Units

When in the PR/ FL operating mode, the DG-700 can display air flow readings on Channel B in units of
3
CFM, m /hr, or l/s. The default air flow unit is CFM. To change the air flow unit for Channel B, press
the UNITS button. The selected air flow units are shown on the gauge display directly below the
Channel B readings. The pressure unit for Channel A is always Pascals when in the PR/ FL mode.

3.6 Changing the Time Averaging Period

To change the selected time averaging period for both Channel A and B, press the TIME AVG button.
The selected time averaging period is shown in the TIME AVG portion of the gauge display. (See
Section 1.5 above for a complete description of the time averaging periods.)

3.7 Using the Baseline Pressure Feature in Pressure/Flow Mode

procedures where the user wishes to display the actual change in building or duct pressure caused by operation of the
Blower Door or duct airtightness testing fan. In order to accurately determine the change in pressure from the test
fan, the user first needs to know the building or duct system pressure (with reference to outside) prior to the test fan
being turned on. This initial baseline pressure reading can be quickly measured and then used to adjust the test
pressure readings to determine the actual change in pressure caused by operation of the Blower Door or duct
airtightness test fan. (See Section 1.6 for an overview of the baseline pressure feature)

3.7.a Example: Using the Baseline Feature During a Blower Door Depressurization Test
- Set up Channel A to measure building pressure with reference to outside (e.g. run tubing from the Channel A
Reference tap to outside and leave the Channel A Input tap open to the building – assumes the gauge is in the
building). Run tubing from the Channel B Input tap to the pressure tap on the Blower Door fan.
- With the Blower Door off and the No-Flow Plate installed, turn on the gauge and put it the PR/ FL mode by
pressing the MODE button.
- Select the Blower Door fan device you will be using by pressing the DEVICE button (Model 3 fan is the default
test device when entering the PR/ FL mode).
The Baseline feature on Channel A allows the user to measure and record a
baseline pressure reading, and then display the baseline adjusted pressure reading.
This feature is commonly used during both building and duct airtightness test
12
Chapter 3 Pressure/Flow Mode
Operating Instructions
for the DG700