Retrotec FanTestic (ATTMA) - Manual (Page 22)

rev-2014-10-27
Page 22 of 58
©Retrotec Inc. 2011-2014
The equation displayed in the Fan Calibration window is the important thing to understand.
𝐹𝑙𝑜𝑤 = (𝑃𝑟𝐵 − 𝑃𝑟𝐴 ∙ 𝐾1) 𝑛 ∙ (𝐾 + 𝐾3 ∙ 𝑃𝑟𝐵) ∙ 𝐾4
This equation defines the relationship between fan pressure, building pressure, and flow. This equation
is used to convert readings of fan pressure (usually on channel B, called FP or PrB in the equation). Note
that Fan pressure should always be a positive value.
There are 2 different ways to enter calibration constants, depending on how the calibration lab supplies
the values to you.
If you are only provide a new K4 value from the lab, you just change the K4 value for each range. K4 is
just a simple multiplier and the units do not matter.

Choose the “Range” from the drop-down,

enter the provided K4 value for that range

Choose the next “Range” from the drop-down, and enter the provided K4 value for that range

Repeat until K4 for all “Ranges” have been entered
When you have been provided with an exponent (n), a K coefficient, and a minimum flow value for each
range from the calibration lab, you must enter the information differently. If this is the case, follow
these steps:

Click the “Ranges” drop down and select a “Range”

Change the units by choosing from the drop-down whatever flow units were used by the
calibration lab

Set K1 and K3 to 0 for the range

Set K4 to 1 for the range