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3.8.14 HIGH RESISTANCE ALARM
Purpose: Alarms heater resistance levels that have increased from the
NOMINAL RESISTANCE set-
ting by more than the selected amount. The
HIGH RESISTANCE ALARM may be used to indicate an
open or a high resistance connection or, when using constant-wattage parallel cables, may indi-
cate the failure of one or more heating zones. It may also be used to monitor a failed series-type
cable or connection in 3-phase applications while minimizing nuisance alarms created by volt-
age fluctuations.
Alarm Mask:
ENABLE or DISABLE
Range: 1 to 250% (deviation from NOMINAL RESISTANCE)
Procedure: Adjust the HIGH RESISTANCE ALARM level to the desired value. The HIGH RESISTANCE
ALARM
must be enabled to adjust the HIGH RESISTANCE deviation.
Notes:
• Using the
LOW CURRENT ALARM feature to ensure that unexpected decreases in current con-
sumption by the heating cable are alarmed is a reliable method of monitoring the integrity of
series-type heating cables. When using parallel-type heaters (zoned constant-wattage or self-
regulating) or in 3-phase installations, the
LOW CURRENT ALARM setting must be chosen as
close as possible to the lowest expected current to detect failed zones, cable degradation, or
a lost phase. The problem with such a close setting is that it inevitably leads to nuisance
alarms, particularly when voltage fluctuations are present. By using the
HIGH RESISTANCE
ALARM
, nuisance alarms due to voltage dips may be minimized.
• Use of the
HIGH RESISTANCE ALARM assumes that the controller power is derived from the
same circuit as the tracing power (either by direct connection or through a step-down trans-
former). Disable this alarm if the controller is powered from a separate circuit.
• Be careful when using this alarm feature with heating cables that exhibit a variable resistance
with temperature. High resistance alarming may not be as effective if the load has a decreas-
ing resistance with temperature.
•No
HIGH RESISTANCE ALARMS will be generated if the measured voltage is below the LOW
VOLTAGE ALARM
setpoint, regardless of whether the LOW VOLTAGE ALARM is enabled. This
stops an alarm from being generated when the circuit power is turned off. If the
LOW VOLTAGE
ALARM
is disabled ensure that the LOW VOLTAGE setpoint is set to a relevant level, otherwise
no
HIGH RESISTANCE ALARMS will occur.
•
HIGH RESISTANCE ALARMS will only be generated if the output switch is on.
3.8.15 HIGH RESISTANCE ALARM FILTER TIME SETTING (V3.11 AND UP)
Purpose: The
HIGH RESISTANCE ALARM FILTER will prevent HIGH RESISTANCE ALARMS from being
indicated until a high resistance condition has existed for the duration of the
HIGH RESISTANCE
ALARM FILTER
time.
Range: 0 to 12 seconds
Procedure: Adjust the HIGH RESISTANCE ALARM FILTER time to the desired value. The HIGH RESIS-
TANCE ALARM
must be enabled to adjust the HIGH RESISTANCE 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.
3.8.16 NOMINAL RESISTANCE SETTING
Purpose: This parameter defines the nominal expected heater resistance. A value must be
entered by the user to allow the
HIGH and LOW RESISTANCE ALARMS to be used. In installations
where the power source may experience periodic fluctuations (surges and/or brown-out condi-
tions), alarming on resistance deviation offers an improved method of monitoring tracer integ-
rity over simple
LOW and HIGH CURRENT ALARMS. Since the ratio of voltage to current is
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