Retrotec DM-2 User Manual

Page 51

Page 51 of 72
©Retrotec Inc. 2012

3. Move across the row and record the flow value beneath the column heading with the actual

Range that was used.

Note: Retrotec 1000, 2000 and 3000 series fans have the same flow curves.

9.8 Fans without reference tube have results adjusted by gauge

When the gauge is connected to a Model 1000, 2000, or 3000 fan, fan pressures are adjusted in the
gauge to compensate for the back pressure on the fan before being used to calculate flow or other
results. Since this adjustment is done by the gauge, they do not require reference tubing (the green
tube) for accurate results. Whenever the gauge measures a positive pressure, the fan flow is towards
the greater pressure, and the gauge makes the necessary deductions from the “PrB” Fan Pressure
before calculating other results. The value shown on the gauge for “PrB” is the actual measured
pressure on channel B, without deductions. See

Appendix A

for more details.

Model 3000SR fans and the DU200 DucTester are self-referenced and include a connection point for
the green tube, which must be connected. Because these fans are self-referenced, the gauge does not
make any adjustments to the Fan Pressure reading before calculating the other results. It is important
that the correct Device selected on the gauge since the chosen Device determines whether or not the
gauge has to do any referencing. If a self-referenced model fan such as the 3350SR series or the
DU200 DucTester is in use, the gauge knows not to adjust the fan pressure before calculating other
results.

9.9 Pressure can overshoot when using the Set Pressure key

When Set Pressure is used to establish 60 Pa for example, the fan will overshoot and reach 90 Pa for a
few seconds before it settles back to the desired 60 Pa. If this is a concern, start the fan on Set Speed
or set to a lower pressure and then use the Jog key to increase the set point in smaller steps. The
speed control in the gauge has been optimized to achieve the desired pressure as quickly as possible
and to remove the overshoot would force the user to wait much longer.

When using the FanTestic software, enter the list of pressures in order of pressure, with the lowest
first. For example, set pressure range from 10 to 60 Pa, rather than 60 to 10 Pa.

Pressures can also overshoot when the range is set too low. Ranges should always be selected so
the fan runs at the fastest possible speed in order to achieve the highest desired test pressure.

To experience the overshoot and understand how to avoid it, perform the following test on the
Retrotec simulator or on a tight room where the leakage can be adjusted.

For example, set Device to 1000, range to C1, time averaging to 10 seconds. Set the leakage area on an
enclosure by adjusting the size of the hole. When using the Retrotec simulator, use the sliding panels
to adjust the size of the hole. Optionally, measure the leakage area with a Door Fan using EqLA10
which you can access using the Mode key. Watch the gauge carefully to detect the peak pressure
reading on Channel A and the peak percent speed on the bottom right-hand of the display.

Device [1000, 2000, 3000]

1000

Range, [C4, C2, C1]