Emerson XM678D - Pressure Transducer and Monitoring System; Single Pressure Transducer Use on Multiplexed Applications; Connecting to the Monitoring System

12 • XM678D I&O Manual 026-1219 Rev 3
6.10.How to Use a Single
Pressure Transducer on
Multiplexed
Applications
A working LAN connection is required (green LED
lit on all XM678D boards of the same LAN). Connect
and configure the pressure transducer only on one
XM678D of the network. Afterwards, the pressure
value read by that single transducer will be used by
each device connected to the same LAN.
To read the pressure value, press the up arrow button
to
access
the fast selection menu and read the value of
the following parameters:
• dPP - measured pressure (only on the master
device)
• dP5 - temperature value obtained from the pressure
value (temperature conversion)
• rPP - pressure value read from remote location
(only for slave devices)
Examples of error messages:
• dPP = Err -> the local transducer read an incorrect
value; the pressure value is out of range of the
pressure transducer or the P5C parameter is
incorrect. Check if any of the above causes the error,
otherwise replace the transducer.
• rPF -> there is an error in the remote pressure
transducer. Check the status of the board (GREEN
LED); if the LED is OFF, then the LAN is not
functioning, otherwise, check the remote pressure
transducer.
Last Checks about the Superheat:
On the fast access menu:
• dPP - the value read by the gauge.
• dP6 - the value read by the temperature probe, the
temperature of the gas on the evaporator outlet.
• SH - the value of the superheat. The nA or err
message means that the superheat cannot be read at
the moment and the value is not available.
6.11.How to Connect the
Monitoring System
• Connect through terminals 36 [-] and 37 [+].
• Use a shielded twisted cable (for example, Belden
8762 or CAT 5 cable).
• The maximum allowable distance is 1 kilometer.
• Do not connect the shield wire to the earth or ground
terminals of the device. Use insulation tapes to avoid
accidental contacts.
Only one controller for each LAN should be
connected to the RS485 connection.
The Adr parameter is the number that identifies each
electronic board. Address duplication is not
permitted; in this case, synchronized defrost and the
communication with the monitoring system are not
guaranteed (the Adr is also the MODBUS address).
Figure 6-6 - Pressure Transducer on Multiplexed Applications
Figure 6-7 - Connecting the Monitoring System
Figure 6-8 - Connecting Monitoring Systems