Siemens LMV37.4 Series Basic Documentation page 48

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Building Technologies
Additional speed-dependent air pressure switch
In this setting, an additional speed-dependent air pressure switch can be connected on
the input.
The input is evaluated depending on the actual recorded speed. The actual speed must
be identified through a speed recording process (see Chapter 12.7 Acquisition of
speed).
Pressure switch ON
Pressure switch OFF
Standard air pressure switch
Figure 21: Additional speed-dependent air pressure switch
No. Parameter
670 Speed air pressure switch OFF
671 Speed air pressure switch ON
The parameters 670 and 671 specify the speed limit of the VSD, from which the
connected additional air pressure switch is supervised. If the current speed is higher
than the ON threshold, the air pressure switch must deliver an ON signal. If the current
speed is lower than the OFF threshold, the air pressure switch must deliver an OFF
signal.
If the current speed is between the two speed limits, no evaluation of the air pressure
switch takes place. The input is supervised in the phases from prepurging to
postpurging and the valve proving phases. An incorrect signal leads to a shutdown.
Intermittent operation must be activated (OEM level) if the speed-dependent air
pressure switch is used as a plausibility check (resulting air pressure) for the
symmetrical speed signal of a PWM fan.
Note!
If the input is configured to additional speed-dependent air pressure switches and the
VSD is deactivated, no evaluation of the air pressure switch signal takes place.
Error Diagnostic
code code
18 0
1
128
Basic documentation LMV37.4...
7 Basic unit LMV37.4
p
a
p
a
< Minimum
load
Meaning for the LMV37.4
Speed-dependent air pressure switch open
Speed-dependent air pressure switch closed
Invalid parameterization of the speed thresholds (speed air
pressure switch OFF  speed air pressure switch ON)
Speed (%)
E.g. E.g.
70 80
CC1P7546en
17.12.2018