Retrotec DucTester 341 - Manual (Page 29)

Page 29 of 83
©Retrotec Inc. 2014
6.7.2. OR Connect to the air handler cabinet
Alternatively, connect a Flex Duct to the air-handler cabinet. Normally this will give the same results as
connecting to a return. In cases where there is no return ducting installed, or where leaks in the return
system are excessive, connecting to the air-handler might be the only option to measure the supply
section of the ducts.
11. Cut a piece of cardboard the same size as the access panel to the blower
compartment of the air handler unit. Cut a hole in the Range 74dle of the
piece of cardboard that is slightly smaller than the square Flange.
12. Put the cardboard piece with the attached Flange onto the opening of the
blower compartment access. Tape the cardboard in place and seal all four
sides of the cardboard panel.
13. Attach the Flex Duct to the Flange and secure it with the Velcro strap.
Ensure that the DucTester has been placed in such a position as to minimize
any major bends in the Flex Duct.
14. Select a location to measure the test pressure that is induced by the
DucTester. This induced pressure will be measured on Channel A of the
gauge.
6.7.3. OR Connect to a return using a Flow Hood
The optional Flow Hood is a faster way to connect to a ceiling
register. Here the system is being pressurized from a ceiling level
return. It is a Pressure Pan with a hole in it, pre-cut to fit the Flex
Duct and a Flange. The blue tube goes into the supply register closest
to the air handler just as before.
When pressing the Flow Hood over the ceiling register, precautions
must be taken to prevent the black rubber weather-strip from
marking light colored walls. Either cover the rubber with clear tape,
or avoid scraping over the painted surface.
Before the registers are covered, and while the air handler is running,
the system’s air handler flow rate can also be measured up to the
capacity of the DucTester. For detailed instructions on how to use a powered Flow Hood to measure
system air handler flow, refer to section 12.3.
Higher air flow rates can also be measured when connected to the air handler itself because then the
exclusive @Pressure feature on the Retrotec gauge can be used to establish an exact flow rate at any
required pressure.
Figure 20: Preparing to
connect to ducts via air
handler
Optional Flow
Hood connector
shown.