Pentair 920 Series Installation, Operating And Maintenance Instructions page 26

INDUSTRIAL HEAT TRACING SOLUTIONS
Important:
• Auto-cycling should always be enabled for normal operation. Disabling this feature should only
be required where the HTC system is monitoring a circuit exercised by some other device or
means. Although this function defeats temperature control and forces output on, the controller
will continue to adjust the output for protection purposes or power limiting (SSR option only).
• Auto-cycling is inhibited if the controller is in the load shedding mode. See section 5.3
on page 52.
• If auto-cycling is enabled, the HTC will always autocycle for 10 seconds when power is initially
applied.
• If auto-cycling is enabled, TS FAIL MODE = OFF and all the control temperature sensors have
failed, the HTC will still perform an autocycle.
• If an alarm condition, with an alarm filter time greater than 0, appears during the auto-cycling,
then the autocycle may be extended (past the 10 seconds) until the alarm filter time has
expired.
3.5.24 autoCyCLe tIme IntervaL
purpose: AUTOCYCLE INTERVAL is the number of hours/minutes between successive heating
circuit integrity tests depending on the AUTOCYCLE UNITS specified.
range: 1 to 240
procedure: Set the AUTOCYCLE INTERVAL to the desired time period.
Important:
• When using proportional ambient contactor mode, the CYCLE TIME setting should be less than
the AUTOCYCLE INTERVAL otherwise au-to-cycling could affect the duty cycle.
• If an AC ALARM becomes active during an autocycle, but the AUTOCYCLE INTERVAL expires
prior to the corresponding ALARM FILTER time, then auto-cycling will continue until the
ALARM FILTER time has elapsed.
• For the earliest possible alarming of heating circuit problems the AUTOCYCLE INTERVAL
should be set to a small value.
3.5.25 autoCyCLe tIme unIts
purpose: The autocycle time units parameter allows selection of minutes or hours for the
AUTOCYCLE INTERVAL setting.
setting: HOURS or MINUTES
procedure: Set the AUTOCYCLE UNITS to the desired time units.
3.5.26 InhIbIt ControL (v3.00 onLy)
purpose: This feature allows the HTC's EXTERNAL INPUT to override the controller's temperature
control and force the output switch off. This is especially useful when the user wishes to turn a
controller or a group of controllers off over the summer months, during maintenance, or when a
line is flowing and does not require heating.
setting: ENABLE or DISABLE
procedure: Enable or disable the INHIBIT CONTROL for the control point being programmed.
Important:
• The EXTERNAL INPUT must also be programmed as INHIBIT before this parameter can be set.
See section 3.6.3 on page 29 for further details.
• If the autocycle feature is enabled, it will continue to function even when the INHIBIT mode is
active.
• Fail-safe mode is inactive if the INHIBIT mode is active.
• Both of the LOW TS ALARMS are inactive if the INHIBIT mode is active.
3.5.27 overrIde sourCe (v3.11 and up)
purpose: An override signal can be sent to the HTC from one of two sources. This override signal
can be used to override the controller's temperature control and force the output switch off or on.
This is especially useful when the user wishes to turn a controller or a group of controllers off over
the summer months, during maintenance, or when a line is flowing and does not require heating.
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