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©Retrotec 2017
If you are sure that the blue tube is reading pressure, there is no blockage in the ducts or tubes, and that
the DucTester is actually reading flow, and “
--
“ still a
ppears, the ducts must be extremely tight; less
than 7 CFM. To get a rough result, cover half the inlet ring with tape which will quadruple the fan
pressure signal. Read the CFM, but divide the answer by two (since half the hole is open). If still reading
“
--
”, cover three quarters of the inlet with tape, read the CFM and divide the answer by four (since only
one quarter of the hole is open).
Instead of doing the calculations, an alternative is to set the Result to be Displayed
” to “
Pressure:
Pa
”and loo
k up the associated flow in Table 9 (for 25 Pa induced duct pressure).
8.6
Cannot achieve test pressure
If the DucTester fan reaches 100% speed on the “
Range 74
” Range Ring before reaching the target
pressure, the fan is not providing enough air flow to reach the target pressure. Perform the following to
reach the target pressure:
1.
Remove a Range Ring.
2.
Change Range Configuration setting on the gauge to match the fan.
3.
Re-adjust DucTester fan speed.
If there is no Range Ring installed (i.e.,
“Open” with no more Range Rings to remove), and the de
sired
test pressure cannot be reached at maximum speed:
4.
If the duct pressure is close to the required test pressure (within 5 Pa), use the
[@]
key to extrapolate
to what the flow would be at the desired pressure.
5.
Try the Duct Leakage to Outdoors test, which will neutralize duct leakage to the house.
6.
Look for large disconnects in the duct system by pressurizing the house with the Blower Door and
putting smoke in front of the registers. Registers with high velocity smoke movement are a good
indication of a potential disconnect behind that register. Fixing the disconnect in the ducts may
reduce the leakage enough to continue testing the duct system.
