Or "Lo" Displayed On Channel B; Changing The Air Handler Flow Units; Changing The Time Averaging Period For The Step 2 Procedure; Test Procedure For Measuring Air Handler Flow - TEC DG-700 Operating Instructions Manual

Once a test device is selected, the configuration of the device (i.e. flow rings, or plate installed) can be selected by
pressing the CONFIG button. The currently selected device configuration is shown in the Config section of the
gauge display.

5.4 "-----"or "LO" Displayed on Channel B

Whenever "-----" or "LO" appears on Channel B in the Step 2 part of the PR/ AH procedure, the DG-700 can not
display a reliable air handler flow estimate. The messages "-----" and "LO" appear on Channel B under the
following three conditions:

"-----" is continuously displayed when either the recorded NSOP reading, or the current TFSOP reading is
below 2 Pa.

"LO" is continuously displayed 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, you should change the test device configuration to match the flow rate being measured (e.g. if using a
Duct Blaster fan, install a flow ring or a smaller flow ring).

5.5 Changing the Air Handler Flow Units

When in the PR/ AH mode, the DG-700 can display air handler flow on Channel B in units of CFM,
3
m /hr, and l/s. The default air flow unit is CFM. To change the flow units for Channel B, press the
UNITS button while in the Step 2 part of the procedure. The selected 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/ AH mode.

5.6 Changing the Time Averaging Period for the Step 2 Procedure

To change the selected time averaging period for the Step 2 part of the PR/ AH procedure, 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 for an overview of the time averaging periods.) During the Step 1 part of
the procedure, the time average feature is always set to long-term average.

5.7 Test Procedure For Measuring Air Handler Flow


5.7.a Step 1: Measuring the NSOP
- Open a window or door between the building and outside to prevent pressure changes in the building during the
test. If the air handler fan is installed in an unconditioned zone (e.g. crawlspace, attic), open any vents or access
doors connecting that zone to the outside (or to the building) to prevent pressure changes in the zone during the
test.
- Make sure all supply and return registers are open and untapped. Replace filters if they are dirty (or keep dirty
filters in place if you want to measure flow in a "as found" condition). Turn on the air handler.
Chapter 5 Pressure/Air Handler Flow Mode
20
Operating Instructions
for the DG700