Retrotec DucTester 341 - Manual (Page 49)

Page 49 of 83
©Retrotec Inc. 2014
This is the total air flow through the duct system provided by the system air handler.
This input is optional, and is only needed if you want the report to display the “Duct Leakage as a % of
Air Handler Flow”.
If this value cannot be found under the Air Handler’s design specifications, it can be measured using
methods described in section 12. It can also be calculated using the forms in Appendix F.
systems.
10.6.3. Baseline pressure
The Baseline pressure is the pressure between the enclosure and the outdoors due to stack, wind, and
flues (with the DucTester fan turned off). Baseline pressure is also called “static pressure”, “bias
pressure,” or “zero Fan Pressure difference”. These terms are used interchangeably with each other in
documents/standards used in the industry.
It is optional to enter a Baseline pressure, since its values are usually very insignificant for duct leakage
test results. This is because not a huge portion of the ducts (as opposed to buildings) are directly
connected to the outdoors.
A method for determining Baseline pressure is by having a digital gauge accumulate readings over an
adjustable time period. The
[Baseline] function on the gauge (from [Settings ] menu allows for this
measurement to be taken. For more information, refer to Retrotec’s DM32 Operation manual.
10.6.4. Enter whether pressurizing or depressurizing (Test direction)
Click to select whether the DucTester fan is setup to depressurize or pressurize the duct system (see
section 6.9).
10.7 Enter readings from this test
10.7.1. Duct Pressure
Enter the Duct Pressure during the test, which is the Channel A reading on the DucTester gauge. The
Duct Pressure in the software are always assumed to be the pressure of the ducts relative to the
pressure of the outdoors.
The Duct Pressure should be a positive number for pressurization, and negative number, with a “-“ sign,
for depressurization. This is important if you have entered a Baseline pressure since the calculated Duct
Test Pressure will then be different depending on the sign.
There are two important points to remember for recording Duct Pressures:
If the [Baseline] function on the gauge was used, you must ensure the Baseline was cleared before
starting the fan. If this is done properly, the Baseline reading on the DM32 gauge (under the Result) will
not show.
Clearing the Baseline value on the gauge ensures that the Channel A pressure on the gauge does not
subtract the Baseline pressure, since the software will subtract this once it is entered. In order to avoid