Red Lion TCU - Manual (Page 37)

Alarm Module (4-AL) (Optional)
The controller may be optionally fitted with the dual alarm option (AL1
and AL2). Some models are equipped only with a single alarm (AL1). One of
three types of output modules (Relay, Logic/SSR Drive or Triac) must be
ordered separately and installed into the appropriate alarm channel socket.
The output modules may be replaced or interchanged (with appropriate
wiring considerations) at any time without re-programming the controller.
With an open sensor, in most alarm configuration modes, the alarm outputs
are up-scale drive (+9999) and with a shorted sensor (RTD only) they are
down-scale drive (-9999). The alarm values can be accessed in configuration
module (4-AL), the unprotected mode, and in the protected mode, if not
locked.
A front panel annunciator illuminates to indicate that the alarm output is on
(AL1 for alarm 1 and AL2 for alarm 2).
Note: When deviation low-acting with positive alarm value (d-LO), deviation
high-acting with negative value (d-HI), or Band inside-acting (b-IN) is
selected for the alarm action, the indicator is “OFF” when the alarm output is
“ON”. These alarm modes latch the outputs when the output is “ON”, when
selected for latched operation.
Caution: In applications where equipment or material damage, or risk to
personnel due to controller malfunction could occur, an independent and
redundant temperature limit indicator with alarm outputs is strongly
recommended. Red Lion Controls model IMT (thermocouple) or model IMR
(RTD) units may be used for this purpose. The indicators should have input
sensors and AC power feeds independent from the other equipment.
Alarm Action (Act1, Act2)
The alarm(s) may be independently configured for one of the following
modes:
Absolute High Acting (A-Hi)
Absolute Low Acting (A-LO)
Deviation High Acting (d-Hi)
Deviation Low Acting
(d-LO) Relative to Setpoint
(Local or Remote)
Band Inside Acting (b-in)
Band Outside Acting (b-Ot)
Second Analog Input Alarm
On models equipped with the Second Analog Input, the alarm(s) may be
configured to monitor the second input reading in addition to the main input.
Refer to the corresponding alarm operation figures for operation modes.
Note that deviation and band alarm modes are only valid for Internal
Cascade operation.
Absolute High Acting -2 (A2Hi)
Absolute Low Acting -2 (A2LO)
Deviation High Acting -2 (d2Hi)
Deviation Low Acting -2 (d2LO) Relative to SP-2, Second
Input (Internal Cascade)
Band Inside Acting -2 (b2in)
Band Outside Acting -2 (b2Ot)
Heater Break Alarm (HcUr)
On models equipped with Heater Current Monitor, either alarm can be
configured as a heater break alarm (Act1 or Act2 = HCur). This alarm
mode is useful to provide early detection of heater element failure before
significant process errors occur. In this alarm mode, the usual temperature
alarm function is disabled. The alarm triggers under two conditions:
1. The main control output (OP1) is “ON” and the heater current reading is
below the alarm value.
This alarm action indicates a failed or advanced age heater element.
2. The main control output (OP1) is “OFF” and the heater current reading is
above 10% of the alarm value.
This alarm action indicates a current leakage through the final actuator.
The heater break alarm value should be set in the region 10% - 20% below
the normal heater current reading. This allowance is necessary to compensate
for drops in line voltage and for temperature dependence in heater current
draw.
Valve Fail Alarm (VFAL)
On models equipped with Valve Positioner (Position mode control only) ,
Alarm #1 may be configured as a valve fail alarm (Act1 = valv). This alarm
mode is useful to provide early detection of valve failure before significant
process errors occur. In this mode, the usual temperature alarm function is
disabled.
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