PCC-IV Instruction Manual (rev. 0.2)
Page 5-14
Section 5 – Configuring Blockware
Modifying a Blockware Configuration
Let’s suppose a customer has developed a simple “Boiler Master” configuration as shown below. The configuration
consists of a steam drum pressure transmitter Input, drum pressure setpoint, a PID control loop, a 4-20 ma “firing
rate demand” Output wired to a control actuator or valve, logic to send the Output to “low fire” (via a discrete Input
from the Flame Safeguard System (FSG) and Auto/Manual control logic. The customer has decided to add an Input
from a Plant Master controller and add high and low boiler drum pressure alarms.
Figure 5.2
Following the recommended approach:
Define the requirements.
We will need to add an input for the Plant Master Demand, a Submaster bias station (to load balance the
boilers), a pushbutton to switch between Plant Master or Local PID control, an LED to show the user which
of these modes the controller is in, and high and low-pressure alarms. The front panel display must also be
modified.
Check the I/O count
The controller has four extra inputs available. If the user wants the Plant Master input to be electrically
“isolated”, an option card will be required. Isolating the Plant Master is not required, but it is a more robust
system design that prevents a single wiring problem from affecting multiple boilers.
Break the configuration down into manageable sections
This is a relatively small change. We will add an alarm section, a Submaster bias section and a control mode
section.
