PEERLESS PUREFIRE PF-850 - Page 57

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BOILER CONTROL: OPERATION
Table 8.31: Multiple Boiler Menu Options (Pixel Display on the front of the boiler)
Boiler
Address
Min 0
This value determines the status of the boiler in a cascade system. The default, “0”, indicates it is a
stand-alone boiler. “1” is to be assigned to the master boiler in the system and “2” up to “16” are
assigned to dependent boilers. In a cascade system, be sure that no boiler address is duplicated.
Max 16
Default 0
Start Delay
Time
Min 1 min
The master control waits for this delay period before bringing on the next boiler. The system
temperature must be less than the target temperature by the “Start Boiler Differential” temperature
for this period of time before operation of another boiler is initiated.
Max 15 min
Default 2 min
Stop Delay
Time
Min 1 min
The master control waits for this delay period before shedding a boiler from the system. The system
temperature must be more than the target temperature by the “Stop Boiler Differential” temperature
for this period of time before operation of a dependent boiler is terminated.
Max 15 min
Default 2 min
Start Boiler
Diff.
Min 1°F (0.5°C)
The master control compares the system temperature to the target value to determine whether to add
a dependent boiler.
for longer than the Start Delay Time, then the next dependent boiler will be initiated.
Max 23°F (13°C)
Default 9°F (5°C)
Stop Boiler
Diff.
Min 1°F (0.5°C)
The master control compares the system temperature to the target value to determine whether to
shed a dependent boiler.
for longer than the Stop Delay Time, then operation of a dependent boiler will be terminated.
Max 45°F (25°C)
Default 9°F (5°C)
Stop All
Boiler Diff.
Min 1°F (0.5°C)
The master control compares the system temperature to the target value to determine whether to
stop all boilers in the cascade system.
for longer than the Stop Delay Time, then operation of all boilers will be terminated.
Max 45°F (25°C)
Default 18°F (10°C)
Max Offset
Up
Min 0°F (0°C)
The master control uses a PID function to scale a target temperature offset for boilers in order to
approach the system target temperature. Increased values are scaled between the “Max Offset Up”
and the system target.
Max 36°F (20°C)
Default 9°F (5°C)
Max Offset
Down
Min 0°F (0°C)
The master control uses a PID function to scale a target temperature offset for boilers in order to
approach the system target temperature. Decreased values are scaled between the “Max Offset
Down” and the system target.
Max 36°F (20°C)
Default 36°F (20°C)
Rotation
Interval
Min 0 (off)
The master boiler determines which boiler starts first based on the “Rotation Interval”. After that it
initiates the next boiler in the address sequence in accordance with the cascade parameters. Boilers
are shed in an order reverse of the initiation.
Max 30 days
Default 5 days
P Value
Min 0
The P- Value is the temperature range where the PID function operates in degrees Celsius and is
symmetrical across the target temperature. The default value of “20” corresponds to 36°F above and
below the target temperature. For example, if the target temperature is 140°F, the temperature range
will be from 104°F to 176°F.
Max 255
Default 20
I Value
Min 0
The “I-term” determines the speed at which the control allows the temperature offset for the
dependent boilers to change. A lower value makes changes to the target more aggressively than a
larger value. This value can be increased for systems which have excess capacity and decreased if
the system does not respond quickly enough.
Max 120
Default 40
D Value
Min 0
The “D-Term” should be set to “0” to most effectively utilize the P-Band of the function. Do not
change this value without specific direction from the factory.
Max 255
Default 0
Slew Rate
Min 1
The slew rate limits the rate of change for target temperatures on dependent boilers. A larger value
allows faster corrections to the dependent boiler offset temperatures.
Max 255
Default 1
If
Target
Temp.
–
System
Temp.
>
Start Boiler
Differential
If
System
Temp.
–
Target
Temp.
>
Stop Boiler
Differential
If
System
Temp.
–
Target
Temp.
>
Stop All
Boiler
Diff.