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Low Voltage Wiring
Low voltage field wiring consists of Room Temperature sensors, 24VDC input/outputs, or Modbus
communication over Cat 5 cables for displays and remote equipment. Low voltage wiring must be run on
the left-hand side of the enclosure and directly terminated on the terminals located on the ECPM03 board.
NOTE: Maximum distance on any low voltage wire is 1000 feet.
NOTE: Use a Cat 5 cable tester to verify that the Cat 5 cable is good. Testing the cable before
installing will eliminate possible communication issues due to faulty Cat 5 cable or ends.
WARNING: Low Voltage Wires Should Never Be Run Together With High Voltage Wires.
1. Room temperature sensor(s): 1 or more room temperature sensors may be used to sense room
temperature or average room temperature. Room temperature sensors must be installed in a safe
location, free of influence from external heat sources. It should be indicative of the average room
temperature and located away from heat-producing appliances, HVAC supply, or direct sunlight. 2-
wire 18 AWG thermistor cable must be used. The room temperature sensor shall be wired according to
the installation wiring schematic, terminals “T1A” and “T1B” for example.
2. LCD faceplate (HMI) is connected to the ECPM03 board through a Cat 5 cable. The faceplate has two
RJ-45 connectors connected together for Modbus. The HMI connects to port J4 or J5 (RJ-45) of the
ECPM03 board. The other RJ-45 port of the HMI faceplate will typically be occupied by a RJ-45 end-
of-line terminator (Part # EOL120A) or can be used as a connection point for another HMI faceplate.
3. End-of-line terminators (Part # EOL120A): Two end-of-line terminators are included in each panel.
They are typically plugged in at the factory on J3 and either on port J4 or in the back of the first HMI
faceplate. If another faceplate or other equipment should connect to a port occupied by an end-of-line
terminator, the resistor shall be removed and placed on the faceplate or equipment that became
connected at the end of the Modbus network. A third end-of-line terminator will be included with the
package if the panel is ordered with 2 or more HMI faceplates. The extra end-of-line terminators will be
mounted on the last HMI if it is connected directly to ECPM03 terminal J5. Otherwise, if the HMIs are
daisy-chained, the third-end-line terminator should be mounted on J5.
4. Modbus Communication: If other pieces of equipment such as an extra VFD are connected to this
panel, a Cat 5 cable will also be used to run the Modbus communication between these devices. The
cable would be plugged in port J3 of the ECPM03 board. The end-of-line terminators should then be
relocated from J3 to the device being added on. Multiple VFDs on one control must be wired in
series using Cat 5 cable. VFDs may be panel mounted or mounted directly onto fans. An end-
of-line resistor must be installed at the last VFD to complete the Modbus network.
5. DDC (Direct Digital Control) Wiring: For communications from a remote Building management
system, low voltage communication wiring is required. This wiring will plug into a gateway that is
mounted in the HVLS panel, which then connects to J1 on the ECPM03 board via Cat 5 connection.
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