Chapter 3
Pressure/Flow Mode
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
CFM
,
m
3
/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
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
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).
12
Operating Instructions
for the DG700
Содержание DG-700
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