Benefits Of Using The @ 50 And @ 25 Modes; Changing The Selected Test Device And Configuration; Or "Lo" Displayed On Channel B - TEC DG-700 Operating Instructions Manual

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4.2.c Benefits of Using the @ 50 and @ 25 Modes:
The @ 50 and @ 25 modes provide four distinct benefits for one-point building and duct airtightness testing:
- The operator no longer needs to waste time adjusting and re-adjusting the fan speed control to achieve a test
pressure of exactly 50 or 25 Pascals – just get close to the target pressure and make your measurement. As long
as the test pressure displayed on Channel A is within 5 Pascals of the 50 or 25 Pascal target pressure, any errors
introduced by estimating the leakage on Channel B will typically be very small (less than 1% - see Tables 4.1
and 4.2 below for more information).
- The leakage estimate displayed on Channel B will typically be very stable because of the continuous
adjustments made using the Channel A test pressure.
- If you can not achieve the target test pressure of 50 or 25 Pascals because the building or duct system is
extremely leaky, a leakage estimate at the target pressure will automatically be displayed on Channel B.
- When in the @ 50 or @ 25 modes, leakage estimates can be displayed as a leakage rate (e.g. CFM @,
3
m /hr @, l/s @ ), or as a leakage area (e.g. square inches @ or square centimeters @) to visualize the
physical size of the measured air leaks.

4.3 Changing the Selected Test Device and Configuration

When in the Pressure/Flow @ 50 or @ 25 modes, the following Energy Conservatory test
devices can be selected:

Model 3 (110V) Minneapolis Blower Door™ fans (BD 3).

Model 3 (220V) Minneapolis Blower Door™ fans (BD 3 220).

Model 4 (220V) Minneapolis Blower Door fans (BD 4).

Series A Minneapolis Duct Blaster® fans (DB A).

Series B Minneapolis Duct Blaster® fans (DB B).
Press the DEVICE button to toggle through the available test devices. The currently selected test device is shown in
the Device section of the gauge display.
Once a test device is selected, the configuration of the device (i.e. flow rings, door position 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.

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

Whenever "-----" or "LO" appears on Channel B in the PR/ FL @ 50 or @ 25 modes, the DG-700 can not
calculate a reliable leakage estimate. The messages "-----" and "LO" appear on Channel B under the following
three conditions:

"-----" is continuously displayed when the test pressure from Channel A is below the minimum test pressures
listed below. Estimating leakage results when the test pressure is below these values may result in large errors.
- 10 Pascals when in the @ 50 mode.
- 5 Pascals when in the @ 25 mode.

"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. install a
flow ring or a smaller flow ring).
Chapter 4 Pressure/Flow @ 50 and @ 25 Modes
15
Operating Instructions
for the DG700