AERCO C-More Controls Manual June 2010 - Manual (Page 100)

C-More Controller for Benchmark, Innovation & KC
USER MANUAL
Page 100 of 162 AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, New York 10913 04/22/14
GF-112 Phone: 800-526-0288 OMM-0032_0E
2. Fire Rate Hold during Warm-Up and Low-Fire-Delay
When an extra boiler is lit off to meet demand, the fire rate of all ignited boilers will be held
at their present level until the newly ignited boiler has completed Warm-up and Low Fire
Delay. When the newly ignited boiler has completed Warm-up and Low Fire Delay, all
boilers will decrease fire rates to approximately 30%. All boiler fire rates will then rise
together to the required fire rate to meet demand.
3. PID Hold during Warm-Up and Low-Fire-Delay
Whenever any boiler is in either Warm-up or Low Fire Delay, the Integral portion of the BST
PID will be frozen in order to prevent the PID from winding up too high, causing the
temperature to overshoot causing an over-temp condition.
4. Setpoint Approach Rate control
To avoid header temperature overshoots, whenever the header temperature nears the
setpoint temperature too quickly to prevent a temperature overshoot, the BST fire rate will
temporarily decrease in order to lower the temperature rise momentum. This feature will
help avoid temperature overshoots due to variable flow as well as other conditions.
This feature is a supervisory function installed as a failsafe (or backup) to normal PID
control.
5. Setback Setpoint gradual decrease
Whenever boilers are running at a high rate and the Setback-Setpoint feature is activated,
the sudden decrease in setpoint will cause the PID to drastically cut back on Fire Rate. This
sudden decrease in fire rate will often cause the boilers to drop below their Stop Levels
causing them to turn off, thereby causing excessive cycling and loss of heating capacity
while the boilers re-ignite.
The Setback-Setpoint gradual decrease feature decreases the setpoint at a slow rate
thereby allowing the PID to recover and preventing any boiler from shutting down if not
required to do so.
6. Next Turn On Valve Position
When all ignited boilers reach or exceed the BST Next on VP value, another boiler will be lit
off to share the load (if one is available).
The default value for Next Turn On Valve Position is 50%.
This feature is also useful if a user wishes to always have as few boilers as possible on at
any one time. Setting the BST Next on VP value to a high number (Example 100%) will only
light off a new boiler if all currently ignited boilers reach their total BTU capacity (100%).
9.2 GENERAL DESCRIPTION
BST is designed to ensure that all boilers in the system operate at maximum efficiency. This is
accomplished by lighting off boilers only if all ignited boilers reach or exceed a defined Valve
Position (Fire Rate). Operating all boilers below the defined Fire Rate “Next on VP” (for Next
Turn on Valve Position) insures that they are firing at their most efficient Fire Rate. One C-More
unit on the BST Modbus Network is defined as the MASTER unit and all other C-More units are
defined as SLAVE units. The Master unit will monitor the system Header Temperature, monitor
all Slave units’ status information and efficiently control all units in order to achieve and maintain
the required BST Setpoint Temperature.