Section 5 Control Module Control Modes; Introduction; Switch Control Modes - nvent RAYCHEM T2000 Installation, Operating And Maintenance Manual

SECTION 5 CONTROL MODULE CONTROL MODES

5.1 INTRODUCTION

5.2 SWITCH CONTROL MODES

There are several different types of control modes in the control module. Some of these modes
require further explanation in order to fully understand and implement their operation.
This section describes the functionality of all the control modes available in the control module
and how to set their associated parameters.
If a control module is not configured as an ATC SLAVE, then four different SWITCH CONTROL
modes may be selected when using the CM 2000+ control module and two different SWITCH
CONTROL modes may be selected when using the CM 2000 control module. The following text
explains these various modes and how they function.
5.2.1 PROPORTIONAL CONTROL FOR CM 2000 CONTROL MODULES
(FOR USE WITH SSRS ONLY)
Proportional control on the CM 2000 is implemented as follows:
• When using the CM 2000 with an SSR to directly control the power applied to the 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).
• This algorithm monitors the temperature of the heating circuit and compares it to the
CONTROL SETPOINT temperature.
• If the temperature sensed by the control sensor is 2°F (1°C) below the CONTROL SETPOINT
temperature, then power is applied to the heating circuit with a duty cycle of 100% --
the control module output is full on.
• If the temperature sensed by the control sensor is equal to the CONTROL SETPOINT
temperature, then the output is turned on with a duty cycle of 50% — the output is on half
the time.
• If the temperature sensed by the control sensor is 2°F (1°C) higher then the CONTROL
SETPOINT temperature, then the control module output will have a duty cycle of 0% —
the output will be off.
• 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
> Setpoint 2°F (1°C)
= Setpoint
< Setpoint -2°F (-1°C)
5.2.2 PROPORTIONAL CONTROL FOR CM 2000+ CONTROL MODULES
(FOR USE WITH SSRS ONLY)
Proportional control on the CM 2000+ is implemented as follows:
• When using the CM 2000+ with an SSR 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).
• This algorithm monitors the temperature of the heating circuit and compares it to the
CONTROL SETPOINT temperature.
• If the temperature sensed by the control sensor is at or below the CONTROL SETPOINT
temperature, then power is applied to the heating circuit with a duty cycle of 100% — the
control module output is full on.
• If the temperature sensed by the control sensor is equal to or greater than the CONTROL
SETPOINT temperature + the PROPORTIONAL BAND setting, then the control module output
will have a duty cycle of 0% -- the output will be off.
Duty Cycle
0%
50%
100%
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