Emerson Nelson CM-1 User Manual
CM-1
CIRCUIT MONITORING SYSTEM
TABLE OF CONTENTS
GENERAL INFORMATION ............................................................................................................... 4
INSTALLATION ................................................................................................................................. 5
Signal When to Monitor Heater ....................................................................................................................................... 6
FIELD WIRING ................................................................................................................................... 6
PROGRAMMING ................................................................................................................................ 8
Circuit Monitor Options ................................................................................................................................................... 9
Power Frequency ........................................................................................................................................................... 10
Alarm Silence Time-out .................................................................................................................................................. 11
Scan Speed ..................................................................................................................................................................... 11
Alarm Reset Auto/Manual .............................................................................................................................................. 11
Programming Option Features ...................................................................................................................................... 12
CM-1 ambient panel start-up procedures ...................................................................................................................... 13
MODBUS RTU Communication .................................................................................................................................... 14
OPERATION ...................................................................................................................................... 15
Alarm Delay ................................................................................................................................................................... 16
Alarm Silence Button ...................................................................................................................................................... 16
CURRENT ADJUSTMENT PROCEDURE ...................................................................................... 17
Digital Display Window ................................................................................................................................................. 18
SPECIFICATIONS ............................................................................................................................. 18
Performance ................................................................................................................................................................... 18
FIELD WIRING DIAGRAM …...………………………………………………………………………... 19
CONTROL DEVICE SCHEMATICS……….…………………….…………………………………...…20
ASSEMBLY DIAGRAM…...……………………………………………………………………………... 21
NOTES …………....……………………………………………………………………………………….... 22
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GA-2129 Rev. 11
Sheet 4 of 22
Jul. 2018
GENERAL INFORMATION
The Nelson CM-1 Circuit Monitor is a scanning microprocessor system which sequentially monitors and
displays each circuit number and the status of each circuit.
The CM-1 is environmentally hardened and requires no protected operative environment. It can be located in
a control room or out in a plant. The low voltage, optically isolated design allows the unit to be installed in
Division 2 Hazardous Locations.
The CM-1 monitoring system:
• Monitors electrical characteristics of each heater circuit, including voltage, amperage,
& continuity.
• Is totally passive.
• Has built in filters to eliminate false alarms due to electrical noise.
• Monitors self-regulating, constant voltage, & series types of heaters.
• Independent of control scheme - will work with ambient or pipe sensed systems.
• Can be retrofitted into existing systems.
The main components of the system include:
• A microprocessor based scanner that interrogates all circuit sensor cards and compares the data to its
programmed parameters. The maximum number of circuits monitored is 24.
• Sensor Card - the sensor card contains the circuitry for 4 heater circuits. Six cards are supplied in a 24
circuit system. The sensor card monitors the current and voltage to each circuit and is interrogated by
the scanner.
• Display - the display shows what circuit is being monitored (.5” readouts). The status of the heater
cable controller is displayed. The L.E.D. bar lights display continuity, current and voltage status of
each circuit.
• Continuity Monitor Device (CMD) - The CMD is a passive component. Parallel type cables require
the attachment of a CMD at the end of each circuit. The microprocessor looks for the device’s
presence every time a parallel circuit is scanned to verify continuity of both bus wires. The CMD
draws a low level capacitive current when connected.
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GA-2129 Rev. 11
Sheet 5 of 22
Jul. 2018
INSTALLATION
When routing conduit to the panel, avoid top entry into the CM-1 enclosure. Top conduit entry provides a
potential moisture path to the electronic circuit boards. Bottom conduit entry is recommended. If top entry
cannot be avoided, avoid the area directly over the circuit boards. Drip loops as shown are recommended for
side and top entry when they cannot be avoided. A drip loop is a dip or bend in the circuit wire to block or
shed moisture, which may follow a wire to the circuit boards.
Top
Display
Drip Loop
Side Entry
Drip Loop
Drip Loop
Drip Loop
Bottom Entry
On-Off Switch
TB-6 (120 VAC)
Top Entry
Enclosure Wall
Sensor Module
Scanner Module
Panduit or
(avoid if possible)
Panduit or
Circuit Board
Circuit Board
DO NOT USE THESE AREAS
FOR CONDUIT ENTRY!
CM-1 Conduit / Wiring Entry for Enclosure
Figure 1
!
WARNING:
Moisture intrusion can damage the CM-1
electronic circuit boards. Do not place conduit
entry directly over the circuit boards.
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GA-2129 Rev. 11
Sheet 6 of 22
Jul. 2018
SIGNAL WHEN TO MONITOR HEATER
The monitor looks for a closed contact signal from a temperature controller before it tries to monitor the
heater for current, voltage, and continuity. The default set-up requires an input signal for each monitor
channel. When a group of heater channels are controlled by a single thermostat (grouped or ambient
control), the panel inputs have to wire in parallel to the single contact signal. Stamped brass jumpers are
provided with the panel to reduce the wiring required for this type of connection.
FIELD WIRING
Typical system wiring diagrams are included in this manual for field wiring. These wiring diagrams are
located at the back of the manual. The PLT-CMD is used to monitor bus continuity on a parallel type heating
cable. After the installing the heater cable on the pipe, connect the PLT-CMD to the opposite end of the
power connection kit.
Silicone
Pipe Clamps
*Fiberglass Tape
*Heater Cable
Stand-off
Sealing Grommet
CMD Device
Conduit Locknut
Gasket
J-Grommet - Overjacket Product
B-Grommet - Base Product
U-Grommet - non-standard construction
Label
Box Cover Gasket
Box Cover
Power Termination
Box Adapter
*ITEMS NOT INCLUDED IN KIT
PLT-CMD Continuity Monitor Device
Figure 2
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GA-2129 Rev. 11
Sheet 7 of 22
Jul. 2018
PNL
Short side branch
(under 10')
Long side branch
PNL
Long side branch
WILL NOT WORK
PNL
Branches are
monitored by
current flow on
process applications.
JB
JB
JB
JB
CM-1
Long side branch
PNL
WILL NOT WORK
PNL
BRANCH / TEE PIPING
(single circuit, multiple cable segments)
GROUPED SEGMENTS
(several separate cables thru single monitor point)
LEGEND
Heater Cable
Pipe
Heater Connection Kit
CM-1, CM-2/1
CMD
CMD
CMD
CMD
CMD
CMD
CMD
CMD
CMD
CMD
CMD
PLT-CMD Cable Connections to CM-1
Figure 3
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GA-2129 Rev. 11
Sheet 8 of 22
Jul. 2018
PROGRAMMING
The CM-1 is shipped with programming to monitor all available circuits. With this configuration, all 24
circuits will be scanned for alarms. Alarm delay is set for 5 minutes, alarm reset is automatic, and the display
speed is fast. Each of these features and options will be covered on the next few pages. However, the system
is suitable to be powered in the existing configuration. When programming, refer to Figure 13, which is also
provided inside the door of the CM-1 enclosure. If all 24 circuits are not active (monitor not required) flip the
corresponding programming switches. Programming can be changed in the field by flipping switches between
on or off.
Figure 4
Programming of the CM-1 is accomplished by flipping the program switches located on the scanner board.
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