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Building Technologies Basic documentation LMV37.4... CC1P7546en
HVAC Products 11 Fan control 01.12.2009
11.8 Speed control
The LMV37.4... controls the fan motor’s speed to the setpoint. To ensure that the actual
speed can still be increased when the maximum is reached, the speed is standardized
when the motor is controlled at 95%. Hence, with a speed setpoint of 100%, a speed in-
crease of 5% is still possible.
The control range of the LMV37.4... is +15% / -10%. If this range is not sufficient, error
80 or 83 can occur.
Error
code
Diagnostic code Meaning for the LMV37.4... system
80 1 Control range limitation at the bottom
2 Control range limitation at the top
&
Note
Internal control with a VSD or PWM fan motor must not be activated. Otherwise,
speed variations can occur, resulting from simultaneous control actions from both the
basic unit and internal control.
11.9 Speed supervision
The fan’s actual speed is acquired by the LMV37.4... and assessed from a safety point
of view. If the fan does not operate at the speed setpoint, speed control makes a correc-
tive action, trying to reach the setpoint. If it is not reached within a certain period of time,
safety shutdown is initiated. To ensure a high level of availability and safety, a number
of monitoring bands with different response times are defined.
Speed deviation in % points Shutdown time
0…0.5% Speed reached → no shutdown
0.6...2% <8 s
2.1...10% <3 s
>10% <1 s
Error
code
Diagnostic
code
Meaning for the LMV37.4... system
83 Bit 0
Valency 1
Lower control range limitation
Bit 1
Valency 2...3
Upper control range limitation
Bit 2
Valency 4...7
Interrupt shutdown due to electromagnetic interference
Bit 3
Valency
≥8
Curve too steep in terms of ramp speed
Bit 4
Valency
≥16
Interruption of speed signal
Bit 5
Valency
≥32
Quick shutdown due to excessive speed deviation
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