Retrotec DucTester 341 - Manual (Page 36)

Page 36 of 83
©Retrotec Inc. 2014
8. Conduct the Duct Leakage test
8.1 Total Duct Leakage
A Total Duct Leakage test measures the total amount of air leakage from a duct system. This includes
leaks to both conditioned spaces, and leaks to unconditioned spaces. Total Duct Leakage is thus the
sum of duct-to-outdoor and duct-to-house leaks. Note that an Exterior door or window must be open in
order to ensure that the pressure inside the building is the same as the pressure outdoors. The
unconditioned space must also be vented (open a window or door from that space if possible, or ensure
there are open roof/crawl space vents).
Pressurization and depressurization tests have the same tubing configurations, shown in Figure 25 for
Total Duct Leakage under depressurization and Figure 26 for Total Duct Leakage under pressurization.
The only difference between the two tests is that for a Depressurization test, the Flex Duct is connected
to the Fan inlet, over top of the Range Rings. The tubing setup is the same for both tests, as illustrated
in the figures, except the Flex Duct is connected to one side or the other of the fan.
Depressurization tests work better since the seal over the register is improved by the negative pressure
in the ducts – the negative pressure sucks the seal tight to the register, whereas under duct
Pressurization, the positive pressure in the ducts tends to push the seals off the registers.
The test diagrams display testing at 25 Pa. For results at 50 Pa, substitute “50” wherever “25” appears.
Figure 25: Total Duct Leakage under depressurization - DucTester and tubing setup.