ProtEX-MAX PD8-6210 Explosion-Proof Analog Input Batch Controller
Instruction Manual
49
Relay Operation Details
Overview
The relays of the controller can serve three roles, as
batch control relays for single or multi-stage batching,
as rate or grand total alarm, or as a sampling relay
based on grand total or rate alarm.
These capabilities include front panel alarm status
LEDs and 4 relays.
The relays used for batch control (total) are activated
when the batching process starts and deactivate when
the batch total is reached. The relays assigned as
pre-close are deactivated when the batch reaches the
preset value minus the pre-close value.
For an example of batch control operation, see
Typical applications for alarms are low flow and high
flow alarms or grand total limit alarms. Note that rate
alarms are only activated during a batch process and
deactivated when the process is stopped.
The relays can also be set for sampling, where the
relay will activate for a specific amount of time after a
certain grand total has been reached (
e.g
. 10 seconds
sample relay activation every 100 gallons batched).
There are three basic ways the relays can be used:
1. Batch Control (Total)
2. High or Low Alarms for Rate or Grand Total
3. Sampling (Based on Grand Total and Sample
Time)
Relays Initialization
Batch control (total) relays will activate when the start
function is enabled, such as when the START button
is pressed. Rate alarm relays will enable and initialize
to their programmed states when the batch process is
started. Grand total alarm relays will initialize to their
programmed state at controller power-up.
Fail-Safe Operation
The following table indicates how alarm relays behave
based on the fail-safe selection for each relay:
Fail-Safe
Selection
Non-Alarm
State
Alarm State
Power Failure
NO
NC
NO
NC
Off
Open
Closed
Closed
Open
Relays in
de-energized state
On
Closed
Open
Open
Closed
Relays in energized
state
Note:
NO = Normally Open, NC = Normally Closed. This
refers to the condition of the relay contacts when the power
to the controller is off.
Front Panel LEDs
The alarm status LEDs on the front panel are available
on all controllers and provide status indication for the
following:
LED
Status
1
Batch Relay 1
2
Batch Relay 2
3
Low Flow Alarm
4
High Flow Alarm
The controller is supplied with alarm points that
include front panel LEDs to indicate alarm conditions.
This standard feature is particularly useful for alarm
applications that require visual-only indication. The
LEDs are controlled by the set and reset points
programmed by the user. When the display reaches a
set point for a high or low alarm, the corresponding
alarm LED will turn on. When the display returns to the
reset point the LED will go off. Note that rate alarms
are only activated during a batch process, and they
are deactivated when the process is stopped.
Latching relays, or relays with manual reset, are not
recommended when using this controller for batch
control, as the manual reset will not be acknowledged
during a batch process, when the rate alarms are
active. For information on latching and manual reset
alarms, see the
Automatic Reset (
Auto
)
In this application, the controller is set up for automatic
reset (non-latching relay). Acknowledging the alarm
while it is still present has no effect on either the LED
or the relay. When the alarm finally goes away, the
relay automatically resets, and the LED also goes off.
Pump Alternation Control
Pump alternation control is not recommended when
using this controller for batch control, as it is used only
in level applications, and not with rate, total, or
batching applications.
Automatic reset only
Condition
LED
Relay
Normal
Off
Off
Alarm
On
On
Ack (No effect)
On
On
Normal
Off
Off
