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• The temperature of the control sensor is constantly monitored and the output duty cycle is
adjusted proportionally according to where the temperature falls within the 0% – 100% band.
Proportional Control Temperature Band For CM 2000+ Control Modules
Control Sensor Temperature Duty Cycle
Š Setpoint+proportional band 0%
= Setpoint+proportional band/2 50%
£ Setpoint 100%
5.2.3 DEADBAND CONTROL (FOR USE WITH CONTACTORS)
Deadband control on the CM 2000 and the CM 2000+ control modules is implemented
as follows:
When using the control module in an application where it controls a contactor, proportional
control cannot be used since this would cycle the contactor too quickly. In these situations,
a deadband control algorithm is used. The output duty cycle is not controlled – instead, the
output is either fully on or completely off. The user may set the DEADBAND value.
The control module monitors the temperature of the heating circuit and compares it to the
CONTROL SETPOINT temperature as in the proportional control mode.
If the temperature sensed by the control sensor is above the CONTROL SETPOINT temperature
by more than the DEADBAND value, the output is turned off.
If the temperature sensed by the control sensor falls below the CONTROL SETPOINT
temperature the output is turned on.
This is a very simple control algorithm but it works very effectively in heat trace applications
where the temperature of a traced system changes relatively slowly.
Deadband Control Temperature Band
Control Sensor Temperature Output State
> Setpoint+deadband Off
£ Setpoint On
When the control sensor temperature is within the deadband, the output does not change its
state. Also, when using deadband control, a contactor is not allowed to toggle faster than once
every 2 seconds.
5.2.4 PROPORTIONAL AMBIENT SSR CONTROL
(FOR CM 2000+ MODULES USING SSRS)
When a CM 2000+ control module using an SSR controls its output using the ambient
temperature, this control mode should be used.
A CM 2000+ control module implements proportional ambient SSR control as follows:
• When using SSRs to directly control the power applied to a heating circuit, the output may
be switched on/off very rapidly. The control module implements proportional temperature
control on a cycle by cycle basis (50 or 60 Hz power line cycle).
• The control module monitors ambient temperature rather than pipe temperature using the
control sensor and compares it to the CONTROL SETPOINT temperature.
• If the temperature sensed by the control sensor is at or below the CONTROL SETPOINT
temperature minus the PROPORTIONAL BAND setting, then power is applied to the heating
circuit with a duty cycle of 100% -- the control module output is fully on.
• If the temperature sensed by the control sensor is equal to or greater than the CONTROL
SETPOINT temperature, then the output will have a duty cycle of 0% -- the control module
output will be off.
• The ambient temperature (using the control sensor) is constantly monitored and the
output duty cycle is adjusted proportionally according to where the temperature falls within
the 0% - 100% band.
Proportional Ambient SSR Control Temperature Band For CM 2000+ Control Modules
Control Sensor Temperature Duty Cycle
Š Setpoint 0%
= Setpoint-proportional band/2 50%
£ Setpoint-proportional band 100%
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