PEERLESS PF-50 Installation, Operation & Maintenance Manual page 54

BOILER CONTROL: INTERNAL WIRING & OPERATION
To cascade PF-50 and PF-80 models, check that the display sub-base has the cascade link as illustrated in Figure 8.10.
Figure 8.11: Interconnection of Cascade Link Wires
f. After operation of the second boiler is initiated,
the Cascade Start Delay Time must elapse before
bringing on additional boilers. Again, in order to
initiate operation of additional boilers one of the
same conditions must be met.
g. When the boiler system approaches its Setpoint,
the boilers will reduce input rates at approximately
equal values. When the input rates of all of the
operating boilers fall below the Next Boiler Stop
Rate, the master control will shut down the last
boiler that started after the Cascade Stop Delay
Time has elapsed.
h. The Calculated Setpoint Max Offset Up and
Calculated Setpoint Max Offset Down are applied
to individual boilers in multiple boiler cascade
operation.
• These temperature offset values are used to
• Increasing these values will cause the system
• Decreasing these values will cause the system
• By increasing the Calculated Setpoint Max
52
Downloaded from www.Manualslib.com
change the response of individual boilers to
the system setpoint.
to react more quickly, but may result in
frequent cycling.
to react more slowly to achieve the setpoint.
Offset Up value, the Master boiler will offset
individual boiler setpoints temperature by a
larger amount in order to achieve the system
setpoint.
manuals search engine
• By increasing the Calculated Setpoint Max
Offset Down value, the boilers will decrease
the boiler setpoints by a larger amount to
achieve the system setpoint.
i. The Rotation Interval is the frequency at which the
Master Boiler will change the Lead boiler in the
sequence.
• For example, if the Rotation Interval is set
to 4 days and there are 4 boilers operating
together, the following chart shows the
operating sequence over the next 25 days.
Table 8.11: Rotation Interval Sequence
Days of Operation
1-5
6-10
11-15
16-20
21-25
7. Multiple Boilers – Boost & Warm Weather
Shutdown (WWSD):
a. To use the Boost function with multiple boilers, the
parameters on the master boiler are used. Boost
parameters set on dependent boilers have no
effect on the system operation.
Start/Stop Sequence
1-2-3-4
2-3-4-1
3-4-1-2
4-1-2-3
1-2-3-4