Thermcraft XST-3-0-36-3V - Manual (Page 147)

Installation and Operation Handbook Load Current Monitoring and Diagnostics
2408 and 2404 Controller D-1
Appendix D LOAD CURRENT MONITORING AND
DIAGNOSTICS
Current flowing in a system of electrical heating elements (the ‘Load’) can be displayed on
the controller by using a TE10 SSR fitted with intelligent current transformer, PDCTX, or an
SSR or contactor with an external PDCTX.
Load current monitoring and diagnostics may be used with any time proportioned output,
fitted in module position 1A, and uses the logic output wires which drive the SSR to return
signals back to the controller These signals represent the RMS value of the load current
during the ON period, or load related alarm conditions. It is not designed for analogue
outputs i.e. phase angle control.
It is also designed for single phase operation only.
There are three modes of operation:-
1. Mode 1
Detects if there is a break in the heater circuit. This includes heater or SSR open circuit. A
single Load Failure alarm message is displayed on the lower readout of the controller.
2. Mode 2
Provides the following:-
Display of true RMS load current On the
lower readout of the controller Displays the true RMS current in the ON
state to the load.
Low current alarm Analogous to Partial
Load Failure (PLF) supplied in some SSRs Provides advanced warning of failure of
one or more heaters in parallel
High current alarm Activated when the
heater exceeds a set limit Typically used where element bunching
may occur
SSR short circuit This will apply full power to the heaters
which could result in an over temperature
condition. This alarm provides early
warning.
Heater failure Indicates open circuit load conditions
3. Mode 5
Provides the same features as mode 2 with two additional alarms. This mode is for use with
contactors or other devices which do not use the PDS logic output from the controller as the
drive signal. For example, a time proportioning logic, relay or triac output to operate a
contactor. Mode 5, therefore, requires an additional input to the controller to display the load
conditions. It uses the LB digital input terminals for this, as shown in Figure D.2.
Current Transformer Open Circuit Alarm is shown if the PDS connection to
PDCTX or SSR become disconnected
Current Transformer Short Circuit Alarm is shown if the PDS connection from
PDCTX or SSR are short circuited