Retrotec DM32, Руководство по эксплуатации

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© Retrotec 2017
“TrueFlow”
2.6.4. Estimate Results with [@ Pressure]
The [@] pressure key enables the gauge to calculate and display the estimated [Channel B] Result that
would be achieved, as if the target pressure was reached (also known as “extrapolation”). The [@
Pressure] key only appears on the Home screen if [Set Speed] or [Set Pressure] functions are used and the
gauge is measuring pressures on Channel A and B.
•
This function is useful in situations when the fan has reached 100% speed and the enclosure
pressure still has not reached the target pressure.
•
Additionally, this function is useful since the measured [Channel A] pressure will usually be slightly
over or under the desired/set pressure, making it difficult to report results that exactly at the
specified pressure.
Tapping [@ Pressure] will toggle the extrapolation function on or off. The label under [Channel B] display
will change to indicate whether [@ Pressure] “ is On ” (e.g., CFM @25.0Pa ) or “ is Off ” (e.g., CFM).
Details of how the gauge calculates the flow at exactly the target pressure, when [Channel A] has not
reached exactly the set target pressure, can be found in
Appendix D .
•
If the [Set Speed] function is used, [@ Pressure] extrapolates the [Channel B] Result to the [Default
@ Pressure] set in the “Settings” screen, using the “n value ” chosen in [Settings].
•
If the [Set Pressure] function is used, [@ Pressure] extrapolates the [Channel B] Result to the
pressure entered for [Set Pressure] , using the “n value ” chosen in [Settings] .
The @ Pressure function provides unique advantages over non-extrapolated results:
•
There is no need to achieve an exact [Channel A] pressure (e.g. to a precision of 0.1 Pa)
•
[Channel B] Results can be obtained even if the test pressure cannot be reached**
**Although the gauge can extrapolate results to any pressure, it is more accurate when the actual
enclosure pressure read on [Channel A] is close to the target pressure. As a rule of thumb, extrapolation
can be used if the actual enclosure pressure reaches at least 80% of the target pressure. If 80% cannot be
reached, more fans are needed to complete the test
(See Retrotec’s Manual-Lge-Multi-Fan Testing ).
Example #1 - Inaccuracy
A 50 Pa building pressure is desired, but only 20 Pa can be reached (due to severe leakiness). In this
instanc
e, the extrapolated results for flow “@ 50 Pa” do not represent the reality of the testing conditions
and might be highly inaccurate.
In the same situation, a 45 Pa building pressure is achieved. The extrapolated “@ 50 Pa” pressure is now
much more accurate, and provides an acceptable result.
2.6.5. Setting “n value” for @Pressure extrapolation