Explanation control functions
The control computer can control the fans modulating. Modulating means that a control (linear or relay) is
activated only during a part of the total cycle time. Modulating control allows minimum ventilation to be achieved
using, for example, a large fan.
Fancom differentiates between the following types of modulating control:
Modulating control with fixed modulation times
Modulating control with optimized modulation times
Rotating modulation
These types are explained in the next sections. This explanation is also important with linear controlled fans.
Linear controlled fans have a minimum ventilation level, for example 30%. This determines below what
percentage the ventilation will modulate, and the ventilation level during modulating. If, for example, the calculated
output of the linear part is 10%, ventilation will run for 10/30th of the cycle time at 30%, and not run for the rest of
the time.
With this type of control enter the fixed cycle time (ON- plus OFF-time). The total cycle is as follows:
Example modulating control with fixed ON-time
Cycle time: 10 minutes
Modulate below %: 30%
Control value ventilation: 15%
If the control value ventilation is lower than 30%, the control computer will use modulating ventilation.
The controllable part will be active for half of the cycle time of 10 minutes, with a ventilation level of
30%. This means an ON-time of 5 minutes and an OFF-time of 5 minutes. The control computer always
controls based on these times.
With optimal modulating control the control computer aims for an optimal ON-time and an optimal OFF-time
entered by the installer. The diagram below shows that the switch off moment and cycle time can vary:
Example - Optimum modulating control (1)
Optimum ON-time: 2 minutes
Maximum cycle time: 10 minutes
Modulate below %: 30%
Control value ventilation: 15%
If the control value ventilation is lower than 30%, the control computer will use modulating ventilation.
The control computer assumes an optimum ON-time of 2 minutes and a ventilation level of 30%. This
means that the optimum ON-time of 2 minutes must be half of the total cycle time. The control computer
calculates a cycle time of 2 x 2 = 4 minutes (2 minutes on and 2 minutes off). In this example the OFF-
time will also be 2 minutes.
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General