Retrotec DucTester 200 Series Residential Applications - Manual (Page 48)

Page 48 of 91
©Retrotec Inc. 2015
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 9. It can also be calculated using the forms in Appendix F.
7.6.3. Leakage Exponent, n
The Leakage Exponent is the "n" value, as read from the top bar of the DM-2 gauge.
It is used to extrapolate results, if you cannot reach your Target test pressure (see section 5.6). This
value is relative to how leaky the ducts are.
If you are unsure of which value to use, enter 0.60 (the default value), which is typical for most duct
systems.
7.6.4. 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] key on the gauge allows for this measurement to be taken. For
more information, refer to Retrotec’s Manual-DM-2 Operation.
7.6.5. 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 3.11).