Thermon TraceNet TCM 18 - Manual (Page 84)

Appendix D Typical TCM18
Control Applications
Example D1 - Ambient Sensing Freeze Protection - Proportional Control with Solid
State Relay Output
When configured with solid state relays, the TCM18 may be used in ambient sens-
ing wide band proportional control. This method of control is ideal in tracing designs
where simple ambient sensing RTD’s and freeze protection is required. In this mode
of control, the TCM18 will (by cycle omission techniques) proportionally increase the
power to the heat tracing as the ambient temperature drops. A typical application for
this type of control might be the freeze protection of water lines in a water treatment
facility. Assume the following heat tracing operating design -
Heat Tracing Type: Self-Regulating Parallel Heater Cable
Minimum Ambient: -20 ◦ F (-29 ◦ C)
Minimum Water Maintain Temp: 50 ◦ F (10 ◦ C)
A typical list of the key TCM18settings is as given below:
Control Parameter Setting
RTD Sensor Setup 1 APC (Single RTD Ambient Sensor
Input)
Control Method Proportional
100% Power On Temperature -20 ◦ F (-29 ◦ C)
Control Band 70 ◦ F (39 ◦ C)
Having set in these values along with appropriate alarm settings, the following con-
trol can typically be achieved.
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