LM
169
G20492-Subject to change. © Belimo Aircontrols (USA), Inc.
WARNING The wiring technician must be trained and experi-
enced with electronic circuits. Disconnect power supply before
attempting any wiring connections or changes. Make all con-
nections in accordance with wiring diagrams and follow all
applicable local and national codes. Provide disconnect and
overload protection as required. Use copper, twisted pair,
conductors only.
Always read the controller manufacturer's installation liter-
ature carefully before making any connections. Follow all
instructions in this literature. If you have any questions, contact
the controller manufacturer and/or Belimo.
Transformer(s)
The LM Series actuators require a 24 VAC class 2 transformer
and draw a maximum of 4 VA. The actuator enclosure cannot
be opened in the field, there are no parts or components to be
replaced or repaired.
– EMC directive: 89/336/EEC
– Software class A: Mode of operation type 1
– Low voltage directive: 73/23/EEC
CAUTION: It is good practice to power electronic or digital con-
trollers from a separate power transformer than that used for
actuators or other end devices. The power supply design in
our actuators and other end devices use half wave rectification.
Some controllers use full wave rectification. When these two
different types of power supplies are connected to the same
power transformer and the DC commons are connected togeth-
er, a short circuit is created across one of the diodes in the full
wave power supply, damaging the controller. Only use a single
power transformer to power the controller and actuator if you
know the controller power supply uses half wave rectification.
Multiple actuators, one transformer
Multiple actuators may be powered from one transformer pro-
vided the following rules are followed:
1. The TOTAL current draw of the actuators (VA rating) is less
than or equal to the rating of the transformer.
2. Polarity on the secondary of the transformer is strictly fol-
lowed. This means that all No. 1 wires from all actuators
are connected to the common leg on the transformer and all
No 2 wires from all actuators are connected to the hotleg.
Mixing wire No. 1 & 2 on one leg of the transformer will
result in erratic operation or failure of the actuator and or
controls.
Multiple actuators, multiple transformers
Multiple actuators positioned by the same control signal may
be powered from multiple transformers provided the following
rules are followed:
1. The transformers are properly sized.
2. All No. 1 wires from all actuators are tied together and tied
to the negative leg of the control signal. See wiring diagram.
Wire length for LM Series actuators
Keep power wire runs below the limits listed in the Fig. 1. If
more than one actuator is powered from the same wire run,
divide the allowable wire length by the number of actuators to
determine the maximum run to any single actuator.
Maximum wire length:
Wire Size Max. Feet. Wire Size Max. Feet
16 Ga 1225 Ft. 20 Ga 400 Ft
18 Ga 725 Ft. 22 Ga 200 Ft
Fig. 1
Example for LM… US: 3 actuators, 18 Ga wire
725 Ft ÷ 3 Actuators = 241.6 Ft. Maximum wire run.
Wire Type and Wire Installation Tips
For most installations, 18 or 16 Ga. cable works well with the
LM24 type actuators. Use code approved wire nuts, terminal
strips or solderless connectors where wires are joined. It is
good practice to run control wires unspliced from the actuator
to the controller. If splices are unavoidable, make sure the
splice can be reached for possible maintenance. Tape and/or
wire tie the splice to reduce the possibility of the splice being
inadvertently pulled apart.
The Belimo …MFT proportional actuators have a digital circuit
that is designed to ignore unwanted input signals (pickup). In
some situations the pickup may be severe enough to cause
erratic running of the actuator. For example, a large inductive
load (high voltage AC wires, motors, etc.) running near the
power or control wiring may cause excessive pickup. To solve
this problem, make one or more of the following changes:
1. Run the wire in metallic conduit.
2. Re-route the wiring away from the source of pickup.
3. Use shielded wire (Belden 8760 or equal). Ground the
shield to an earth ground. Do not connect it to the
actuator common.
LM Series Actuators with Terminal Strip
LM…-T actuators feature an external screw terminal strip on
the top of the actuator housing (instead of cable). Connections
are numbered and a wiring schematic is shown next to the ter-
minal strip. The terminals are designed for 26 to 14 GA wire.
Installation Instructions
General Wiring
Brushless DC Motor Operation
Belimo’s Halomo Brushless DC motor spins by reversing the poles
of stationary electromagnets housed inside rotation permanent mag-
nets. The electromagnetic poles are switched by a microprocessor
and a special ASIC developed by Belimo. Unlike the conventional
DC motor, there are no brushes to wear or commutators to foul.
Overload protection
The LM24-3 US and LM24-SR US actuators are electronically
protected from overload at all angles of rotation by digital tech-
nology in the ASIC. The ASIC circuitry constantly monitors the
rotation of the Brushless DC motor inside the actuator and
stops the pulsing to the motor when it senses an overload.
The motor remains energized and produces full rated torque
when overload.
End stop filtering enables the actuator to ignore short controller
pulses while at the end position, i.e. pulses that are in the same
direction as the end stop, while already at the end position.
Electrical Operation
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