nVent RAYCHEM Elexant 4010i/4020i User Manual
RAYCHEM-AR-H60624-40X0iOpsManual-EN-1905
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3.1.2.1 On/Off (Default)
The controller monitors the temperature of the heating circuit and compares it to the setpoint tempera-
ture. If the measured temperature is above the control temperature setpoint by more than the Deadband
value, the output is turned off. If the control temperature falls below the control temperature setpoint, the
output is turned on. When the control sensor temperature is within the dead band, the output does not
change its state.
Control Sensor Temperature
Output State
Se deadband
Off
Setpoint or below
On
Within deadband
No change
Table 3 - On/Off Control Status
3.1.2.2 PASC (Proportional Ambient Sensing Control)
The PASC algorithm maintains the temperature of the device being heated using the ambient tempera
-
ture, while minimizing energy consumption and wear on the contactor.
It uses the measured ambient
temperature, desired maintain temperature, minimum ambient temperature assumption used during
design, and size of the smallest pipe diameter to calculate how long the heater should be on or off to
maintain a near-constant pipe temperature.
PASC takes advantage of the fact that the heat loss from a pipe is proportional to the temperature differ-
ence between pipe and the ambient air. This is true regardless of heater type, insulation type, or pipe size.
Once the heat tracing and insulation on a pipe has been designed to balance heat input with heat loss
and maintain a particular temperature, the main variable in controlling the pipe temperature becomes the
ambient air temperature.
This approach greatly reduces the amount of energy used in ambient temperature control applications
versus traditional ambient temperature control.
3.1.2.3 Proportional
The Proportional algorithm monitors the temperature of the heating circuit and compares it to the
setpoint temperature. If the measured temperature is at or below the setpoint temperature, then power
is applied to the heat trace circuit with a duty cycle of 100%. If the temperature is equal to or greater than
the setpoint tempe proportional band, then the relay output will have a duty cycle of 0%. The tem
-
perature is constantly monitored, and the output duty cycle is adjusted proportionally once per second.
Control Sense Temperature
Duty Cycle
Se proportional band
0%
Se proportional band / 2
50%
Setpoint
100%
Table 4 - Proportional Control vs Duty Cycle
Note:
When using Solid State Relay (SSR) and Analog SSR modes to precisely control the power applied
to a heating circuit, the output may be switched on/off very rapidly. Therefore, the proportional control
mode should not be used with EMR (contactor) output types.
3.1.2.4 Always On
The controller output is permanently switched on and power is applied to the heat trace circuit.
3.1.2.5 Always Off
The controller output is permanently switched off and power is removed from the heat trace circuit.
3.1.3
Output Overrides
This section lists situations where the normal control decision can be overridden: e.g. Digital Input
(Hand/Off/Auto), Load Shedding, Temperature Cut-out, Protection Trips, Start-up delay, Configuration
Loss, and Limiter Trip.
