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3.8.1 LOW LOAD CURRENT ALARM
Purpose: Alarms current levels that are lower than a preset limit for the application. Monitoring
for lower-than-expected current levels may be an effective means of continuity monitoring. See
also
HIGH RESISTANCE ALARM in section 3.8.14 on page 39.
Alarm Mask:
ENABLE or DISABLE
Range:0.3 to 100.0 amps
(
CURRENT TURNS RATIO = 1.00)
Procedure: Adjust the LOW CURRENT ALARM level to the desired value. Note that the LOW CUR-
RENT ALARM
must be enabled in order to adjust the LOW CURRENT ALARM level. Also note that
the
LOW CURRENT ALARM level is affected by the CURRENT TURNS RATIO setting. The absolute
maximum adjusted
LOW CURRENT ALARM level is 300.0 amps. The absolute minimum adjusted
LOW CURRENT ALARM level is 0.1 amps. See section 3.5.22 on page 26 for more information
regarding the
CURRENT TURNS RATIO function.
Notes (V3.00 only):
• To minimize nuisance
LOW CURRENT ALARMS, the HTC must detect a current level less than
the
LOW CURRENT ALARM setpoint for a period longer than approximately 20 consecutive sec-
onds.
• For series-type heating cables, adjusting the
LOW CURRENT ALARM to 50% of full load current
will properly alarm a problem and reduce nuisance alarms due to voltage dips. Parallel
heaters should be adjusted to a level as close as possible to full load current but lower than
the current at worst-case voltage. The low current setting as a percentage of full load current
will vary depending on the facility and its power system.
•A
LOW CURRENT ALARM may also result from a switch failed open. The controller cannot
detect a switch failure due to no current. A no current condition would be identified by a
LOW
CURRENT ALARM
(if enabled) and the analog value reported with the alarm will be 0.0 A.
• It may be advantageous to consider using the
HIGH RESISTANCE ALARM to indicate a cable
fault when using certain types of heaters. See sections 3.8.12 on page 38 and 3.8.14 on
page 39 for an explanation of the resistance alarming feature.
3.8.2 LOW LOAD CURRENT ALARM FILTER TIME SETTING (V3.11 AND UP)
Purpose: The
LOW CURRENT ALARM FILTER will prevent LOW LOAD CURRENT ALARMS from being
indicated until a low current condition has existed for the duration of the
LOW CURRENT ALARM
FILTER
time.
Range: 0 to 12 seconds
Procedure: Adjust the
LOW CURRENT ALARM FILTER time to the desired value. Note that the LOW
CURRENT ALARM
must be enabled in order to adjust the LOW CURRENT ALARM FILTER time.
Notes:
• If an alarm condition appears and then disappears before the alarm filter time has expired,
the filter timer is reset and the alarm condition must exist again for the entire alarm filter time
before the corresponding alarm will be indicated.
• If the user resets an alarm while the alarm condition is still exists, the alarm will not be indi-
cated again until the entire alarm filter time has expired.
3.8.3 HIGH LOAD CURRENT ALARM
Purpose: Alarms current levels that are higher than a preset limit for the application.
Alarm Mask:
ENABLE or DISABLE
Range: 0.3 to 100.0 amps
(
CURRENT TURNS RATIO = 1.00)
Procedure: Adjust the HIGH CURRENT ALARM level to the desired value. Note that the HIGH CUR-
RENT ALARM
must be enabled in order to adjust the HIGH CURRENT ALARM level. Also note that
the
HIGH CURRENT ALARM level is affected by the CURRENT TURNS RATIO setting. The absolute
maximum adjusted
HIGH CURRENT ALARM level is 300.0 amps. The absolute minimum adjusted
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