Pentair 920 Series - Proportional and Deadband Control Modes

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EN- Raychem920series-IM-H5687405/15
INDUSTRIAL HEAT TRACING SOLUTIONS
5.2.3 PROPORTIONAL AMBIENT SSR CONTROL (FOR USE WITH SSRS ONLY)
When an HTC using an SSR is used to control the output using the ambient temperature, this
control mode should be used.
Proportional ambient SSR control on the HTC is implemented 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 controller implements proportional temperature control on a
cycle-by-cycle basis (50 or 60 Hz power line cycle).
• ThisalgorithmmonitorsambienttemperatureandcomparesittotheCONTROLSETPOINT
temperature. If the temperature of the control sensor is at or below the CONTROL SETPOINT
temperature minus the PROPORTIONAL BAND setting, power is applied to the trace with a duty
cycle of 100%—the controller output is fully on.
• IfthetemperaturesensedbythecontrolsensorisequaltoorgreaterthantheCONTROL
SETPOINT temperature, the output will have a duty cycle of 0%—the controller 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 Ambient SSR Control Temperature Band
Control Sensor Temperature Duty Cycle
Setpoint 0%
Setpoint - proportional band/2 50%
Setpoint - proportional band 100%
IMPORTANT: The load shedding fail-safe mode is not supported when using proportional ambient
SSR control, since ambient temperature is being monitored rather than pipe temperature.\
5.2.4 PROPORTIONAL AMBIENT CONTACTOR CONTROL
(FOR USE WITH EXTERNAL CONTACTORS)
When an HTC using a contactor is used to control the output based on the ambient temperature
this control mode should be used.
Proportional ambient contactor control on the HTC is implemented as follows:
• Theoutputmaynotbeswitchedon/offrapidlywhenusingacontactor,soproportional
temperature control is implemented by applying the required duty cycle over the selected
CYCLETIME.
• TheoutputisfullyonforaportionoftheCYCLETIMEasdeterminedbythecalculatedduty
cycle,anditwillbecompletelyoffforthere-mainderoftheCYCLETIME.
• Thedutycycleiscalculatedeachtimetheoutputtoggles,basedontheambienttemperature,
PROPORTIONAL BAND setting, and the CON-TROL SETPOINT temperature setting.
• ThecontrollermonitorstheambienttemperatureandcomparesittotheCONTROLSETPOINT
temperature as in proportional ambient SSR control. If the temperature of the control sensor
is at or below the CONTROL SETPOINT temperature minus the PROPORTIONAL BAND setting,
power is applied to the trace with a duty cycle of 100%. The controller output will be fully on for
1/30thoftheCYCLETIMEsettingbeforethedutycycleiscalculatedagain.
• IfthetemperaturesensedbythecontrolsensorisequaltoorgreaterthantheCONTROL
SETPOINT temperature, the output will have a duty cycle of 0%. The controller output will be off
for1/30thoftheCYCLETIMEsettingbeforethedutycycleiscalculatedagain.
Proportional Ambient Contactor Control Temperature Band
Control Sensor Temperature Duty Cycle
Setpoint 0%
Setpoint - proportional band/2 50%
Setpoint - proportional band 100%
IMPORTANT: The load shedding fail-safe mode is not supported when using proportional ambient
contactor control, since ambient temperature is being monitored rather than pipe temperature.
If an AC alarm with an alarm filter time greater than 0 is detected, the contactor will not toggle
until the alarm filter time has expired.