Retrotec DucTester 200 Series Residential Applications - Manual (Page 42)

Page 42 of 91
©Retrotec Inc. 2015
3. Re-adjust DucTester fan speed.
If the Range Ring installed is “Low”, (the one with the smallest hole), there are no more Range Rings to
install, and “TOO LOW” or “---“ still appears:
1. Make sure “Range Config” on the gauge is “Low” to match the installed Range Ring.
2. Check that the blue tube is connected to the gauge and then check that it is reading pressure – put a
finger on the open end of the blue tube and ensure that the “PrA” reading changes. If it does not,
then the tube is blocked or pinched.
3. Check that there is no blockage in the ducts between the DucTester and the register containing the
blue tube. To do this, move the blue tube to a different register and compare the reading on “PrA” to
the original reading. If the pressures in the two locations are not similar, there may be blockage in
the duct system that needs to be removed.
4. Check that the DucTester is actually reading properly on Channel B. To do this, open up a taped
register to provide enough leakage to get a reading, and then increase the pressure to 25 Pa or 50 Pa
on “PrA”. If the flow still reads “TOO LOW” then the yellow or green tubes could be blocked or
disconnected.
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 "TOO LOW" or “---“ still appears, 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 “TOO LOW”, 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 gauge “Mode” to “PrB”, (Pressure on
Channel B), using the [Mode] key and look up the associated flow in Table 10 (for 25 Pa induced duct
pressure) or Table 11 (for 50 Pa induced duct pressure).
5.6 Cannot achieve test pressure
If the DucTester fan reaches 100% speed on the “Mid” or “Low” 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 Config] on the gauge to match the fan.
3. Re-adjust DucTester fan speed.
If the no Range Ring installed (i.e., “Open” with no more Range Rings to remove), and the desired test
pressure cannot be reached at maximum speed:
1. If the duct pressure is close to the required test pressure (within 5 Pa), use the [@ Pressure] key to
extrapolate to what the flow would be at the desired pressure.
2. Try the Duct Leakage to Outdoors test, which will neutralize duct leakage to the house.
3. 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.