Pentair 920 Series - Page 39

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EN- Raychem920series-IM-H5687405/15
INDUSTRIAL HEAT TRACING SOLUTIONS
the overcurrent trip limit and the controller will not be able to soft start the trace circuit. If this
condition persists, please contact your nearest sales office for recommendations and solutions to
this problem.
3.8.18 SWITCH FAILURE ALARM
Purpose: The purpose of the SWITCH FAILURE ALARM is to indicate that an output switch failure
has occurred. The controller determines that if the output switch is turned off and there is load
current present, then the output switch has failed closed and the alarm is latched on.
Alarm Mask: ENABLE or DISABLE
Procedure: Enable or disable the alarming of an output switch that has failed in the closed
position.
IMPORTANT: The SWITCH FAILURE ALARM should always be enabled. A high temperature
condition as a result of a failed circuit can only be caused if the output switch fails closed. When an
output switch fails closed, the controller cannot turn the tracer power off, therefore no protection
features are available (ground-fault trip, power limiting, etc.). If a SWITCH FAILURE ALARM is
detected, the unit should be serviced immediately.
3.8.19 HTC RESET ALARM
Purpose: The HTC RESET ALARM is used to indicate:
1. Power to the HTC has been interrupted and subsequently restored.
2. A transient has caused the HTC’s microprocessor to restart.
3. An internal condition has caused the HTC’s microprocessor to restart its program.
Alarm Mask: ENABLE or DISABLE
Procedure: Enable or disable alarming on reset as desired.
IMPORTANT: Normally the HTC RESET ALARM is left disabled since powering the controller off
and on for maintenance or troubleshooting would require the user to reset this alarm every time.
If the particular installation includes a Model 780/GCC-9000, this alarm may be left enabled
since resets are not considered normal occurrences and the Model 780/GCC-9000 provides the
capability to easily log and reset alarms such as these. The difference in time between when a
COMMUNICATIONS FAIL ALARM and an HTC RESET ALARM are logged provide an indication of
how long the circuit has been “OFF.”
3.8.20 CIRCUIT BREAKER LIMITING STATUS (SSR ONLY)
Purpose: The circuit breaker limiting feature is always enabled when using an SSR output switch
and is intended to prevent the circuit breaker immediately upstream of the controller from tripping
during a temporary overcurrent condition. Enabling this alarm will only inform the user that circuit
breaker limiting is currently active.
Alarm Mask: ENABLE or DISABLE
Procedure: Adjust the CIRCUIT BREAKER CURRENT RATING setting to the heating circuit breaker
size (i.e. 15.0 or 20.0 amps). Enable or disable the alarm as required. The CIRCUIT BREAKER
LIMITING ALARM need not be enabled in order to adjust the CIRCUIT BREAKER CURRENT RATING
setting.
IMPORTANT:
• Thisisanon-latchingalarm.
• Thisalarmisadvisory.Ifthemeasuredcurrentexceedsthelevelthatwouldcausethe
upstream circuit breaker to release, the HTC will begin to switch the SSR ON and OFF rapidly to
limit the average current to an acceptable level.
3.8.21 POWER-LIMITING STATUS (SSR ONLY)
Purpose: The power-limiting feature is always enabled when using an SSR output switch and is
intended to limit the average amount of power that is applied to the trace circuit. The controller
measures the voltage and current of the trace circuit and will vary its output switch to limit the
amount of power applied to the trace to the value set by the MAXIMUM POWER setting. Enabling
this alarm will only inform the user that power limiting is currently active.
Alarm Mask: ENABLE or DISABLE