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Building Technologies Division User Manual LMS14… CC1U7471en
6 The settings in detail 28.01.2015
6.35.12 Filter for fan speed setpoint (OEM)
The fan speed setpoint can be filtered with a Pt1 algorithm. If there is a setpoint change
from a lower to a higher value, the change can be slowed down with a Pt1 filter
constant. If the setpoint changes from a higher to a lower value, there a 3 Pt1 filter
constants to slow down the setpoint change and thus the current fan speed. The band
of the 3 Pt1 filter constants from a higher to a lower value can be selected with 2
threshold parameters for the fan speed. These fan speed threshold parameters are only
valid for a change from a higher to a lower value.
7471d65e/0311
Figure 105: Block circuit diagram Pt1 speed-setpoint filter
Diff setpoint filter [5285.1] make it possible to distinguish between different filter time
constants depending on the phase.
If Diff setpoint filter [5285.1] is set to Yes, filter time constants Pt1 time const 4 drop
[5283.1] and Pt1 time const 1 incr [5284.1] apply in phases TI and MOD.
In all other phases, the following filter time constants are used:
Pt1 time const 1 drop [3694.1],
Pt1 time const 2 drop [3695.1],
Pt1 time const 3 drop [3696.1],
Pt1 time const 2 incr [3697.1],
Pt1 upper spd falling [3698.1], and
Pt1 lower spd falling [3699.1].
If Diff setpoint filter [5285.1] is set to No, the following filter time constants are used in
all phases:
Pt1 time const 1 drop [3694.1],
Pt1 time const 2 drop [3695.1],
Pt1 time const 3 drop [3696.1],
Pt1 time const 2 incr [3697.1],
Pt1 upper spd falling [3698.1], and
Pt1 lower spd falling [3699.1].
In that case, Pt1 time const 4 drop [5283.1] and Pt1 time const 1 incr [5284.1] have no
impact.
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