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Nelson™ Heat Trace CM-1 Microprocessor Based Heater Cable Monitoring System
Nelson™ Heat Trace™ Type CM-1 Microprocessor Based Heater Cable Monitoring System
Nelson™ Heat Trace CM-1 microprocessor based heater cable monitoring system continually monitors the status of both series and parallel styles of electric heat tracing cables and panels.
The CM-1 monitors the supply voltage and current flow to each heating device. With the addition of continuity monitoring devices (CMD), this system monitors both bus wires in parallel styles of heating cable. When used in conjunction with ground fault branch breakers, the CM-1 serves as an automatic alarm system for any ground fault condition.
Nelson™ Heat Trace CM-1 Microprocessor Based Heater Cable Monitoring System


Certifications and Compliances
ETL Listed to UL and CSA Standards: Hazardous (Classified) Locations
Class I, Division 2, Groups B, C, D; Temperature Code: T3C (+160 °C), T3A (+180 °C)
NEMA Type 4, 4X
Heat Trace Load
30 Amps @ 300 Vac maximum
Ambient Temperature
-40 °C to +55 °C (-40 °F to +130 °F)
Single line numeric LED circuit indication. LED bar indicators for alarm status
Control Power Input
120 Vac
Voltage Range
85 to 300 Vac
Current Range
0.05 to 30.0 Amp
Requires additional CMD device for each monitored circuit
Alarm Contacts
Common for all alarms.
Temperature Control Input
Requires dry contact from control device(s) or -V control input option for monitoring of temperature control device
RS-485, Modbus™ RTU protocol


  • The cable monitoring system is mounted in a NEMA 4 or 4X enclosure that can be wall or rack mounted. The unit is normally located in close proximity to the breaker panel feeding the heat tracing system. The system is available in configurations up to 48
  • Scanner board: The system is controlled by a microprocessor-based scanner that systematically interrogates all circuit parameters and compares actual vs programmed data. The scanner board is environmentally hardened to allow the system to be installed in
  • Display unit: The display unit is visible through a protective Plexiglas panel in the door of the assembly. All indicators are LED to provide visibility in all light conditions. The unit displays the circuit being monitored on 0.5 inch read outs and heat
  • Sensor cards: The sensor cards monitor the electrical parameters of each heating circuit. Each sensor card monitors up to 4 circuits for voltage, current and continuity. An adjustable potentiometer allows the low current alarm level to be set for each ci
  • Continuity monitoring device: For continuity monitoring, parallel types of heating cables require the attachment of a bus monitor device at the end of each heater circuit. This device is totally passive and generates no electrical noise or signals that m