90
J20741 - Subject to change. © Belimo Aircontrols (USA), Inc.
®
If the shaft extends at least 3/4” from the duct, follow these
steps:
1. (See Fig. D) Move damper blades to the fail-safe position (a).
2. Determine the best orientation for the universal clamp on the
back of the actuator. The best location would be where you
have the easiest access to the V bolt nuts on the clamp.
3. Engage the clamp to the actuator as close as possible to
the determined location.
4. Lock the clamp to the actuator using the retainer clip.
5. Mount the spring return actuator to the shaft. Tighten the
universal clamp, finger tight only.
6. Mount the anti-rotation strap at the base of the actuator.
Do not tighten the screws.
7. Remove the screw from one end of the mounting bracket
and pivot it away from the actuator.
8. Loosen the universal clamp and, making sure not to move
the damper shaft, rotate the actuator approximately 5° in
the direction which would open the damper.
9. Verify that the damper is still in its full fail-safe position.
10. Tighten the universal clamp to the shaft.
11. Rotate the actuator to apply pressure to the damper seals
(b) and re-engage the anti-rotation strap (c).
12. Tighten all fasteners.
13. Use IND-LF accessory if position indication is needed.
Installation Instructions
Short Shaft Mounting with IND-LF Position Indicator / Airtight Damper Procedure
Initialization of the LF24-SR US and LF24-MFT… US
When power is applied, the internal microprocessor recog-
nizes that the actuator is at its full fail-safe position and
uses this position as the base for all of its position calcula-
tions. This procedure takes approximately 15 seconds.
During this time you will see no response at the actuator.
The microprocessor will retain the initialized zero during
short power failures of up to 25 seconds. When power is
applied during this period, the actuator will return to normal
operation and proceed to the position corresponding to the
input signal provided. For power failures over 25 seconds,
the actuator will be at it fail-safe position and will go through
the start up initialization again.
Motor position detection
Belimo brushless DC motors eliminate the need for poten-
tiometers for positioning. Inside the motor are three “Hall
Effect” sensors. These sensors detect the spinning rotor
and send pulses to the microprocessor which counts the
pulses and calculates the position to within 1/3 of a revolu-
tion of the motor.
Overload protection
The LF, on-off actuators are electronically protected against
overload. The LF, On-off actuators have an internal current
limiter which maintains the current at a safe level which will
not damage the actuator while providing adequate holding
torque.
The LF24, modulating actuators (LF24-SR US, LF24-3 US,
LF24-MFT US) are protected against overload by digital tech-
nology located in the ASIC. The ASIC circuitry constantly mon-
itors the rotation of the brushless DC motor inside the actuator
and stops the pulsing to the motor when it senses a stall con-
dition. The motor remains energized and produces full rated
torque during stall conditions. The actuator will try to move in
the direction of the stall every 2 minutes, for a period of 32
minutes. After this, the actuator will try again every 2 hours.
Operational Information for LF24-SR US and LF24-MFT… US Actuators
min 3/4”
[20]
IND-LF Position Indicator
(optional)
Fig. D
0
1
2
4
5
6
7
8
9
L
C
b
c
a
.2
.4
.6
.8
1
CW
0
®
Short Shaft
Mounting
Short Shaft
Mounting
