27
Note: When the CURRENT TURNS RATIO has been set appropriately, the HTC will calculate the cir-
cuit power using the adjusted current and voltage readings. Current alarms, as well as the switch
and circuit breaker limiting functions, also use the adjusted circuit currents.
3.5.23 AUTOCYCLE ENABLING
Purpose: The autocycle function momentarily (approximately 10 seconds) applies power to the
heating circuit at the selected interval. It is used to test the integrity of the heating circuit. Alarms
present at the time of autocycle then become latched and remain active after the completion of
the autocycle function. Auto-cycling effectively eliminates the need for preventive maintenance
by automatically verifying the heating circuit integrity.
Setting:
ENABLE or DISABLE
Procedure: Enable or disable the auto-cycling feature as desired. If the feature is disabled, you
will not be prompted to enter the
AUTOCYCLE INTERVAL or AUTOCYCLE UNITS.
Notes:
• 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 ini-
tially 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 cir-
cuit integrity tests depending on the
AUTOCYCLE UNITS specified.
Range: 1 to 240
Procedure: Set the
AUTOCYCLE INTERVAL to the desired time period.
Notes:
• When using proportional ambient contactor mode, the
CYCLE TIME setting should be less
than the
AUTOCYCLE INTERVAL otherwise auto-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.
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