Red Lion TCU - Manual (Page 65)

HEATER CURRENT MONITOR OPTION
This option allows monitoring of heater element current controlled by the
TCU via the main output OP1. The actual heater current is viewed in the lower
display. This is useful in determining how much the heater element has aged,
if the element open circuited or if the element has a ground fault. A Heater
Break Alarm can be programmed to signal the event
before process damage
occurs (See Alarm Action, page 29). Normally, the heater current alarm value
is set for 10-20% below the actual heater current value. This allows for line
voltage variations and a small amount of heater element oxidation (aging).
The Heater Current Monitor is for single phase power monitoring. For
3-phase heating systems, Red Lion Controls Model IMH (5 ampere Current
Transformer Indicator) can be used to monitor individual line phases.
Example : A 50:0.1 current transformer is used. The actual observed heater
current is 38 amperes. The heater fault alarm is used and set to trigger at
32.0 amperes (38A * 85%). Placing the current transformer in the ground
(neutral) lead allows for heater ground fault detection. The following lists
the parameters for configuring the Heater Current Monitor with Alarm
fault detection.
HCur - 50.0 Set full scale heater current equal to current
transformer rating
ACt1 - HCur Program Alarm #1 for heater fault action
AL1 - 32.0 Set heater current alarm for 32.0 amperes
57
Figure 27, Heater Current Monitor Diagram