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1
Service
Table 1I Cascade (This table lists control module parameters; use the sub-tab under the Setup tab to access them.
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Cascade Address
Cascade Status
Cascade Type
Cascade Set point: Offset
Cascade Set point: Differential
Max Cascade Cond. Set point (F)
Max Cascade Non-Cond Set point (F)
Block Time Switching Boiler On / Off
Minimum Next On Time
Rate % to Switch On Next Boiler
Rate % to Switch Off Last Boiler
Member Size Code*
Redundant Leader
Cascade
Cascade Address
The boiler designated as the Leader needs to be programmed
with address 0. All the Member boilers require addresses
from 1 to 7, and the addresses must be different for each
Member. The addresses can be in any order, regardless of
the order in which the units are wired together. The outdoor
air (if used) and system supply sensor must be connected to
the Leader boiler.
Cascade Status
The boiler is part of a group of units sequenced together. The
designated Leader unit determines the total output needed
from the group based on the set point and controlling sensor
reading. It assigns portions of the output to itself (Leader)
and the Member units. When Cascade is active, each boiler
in the group requires a unique address.
Cascade Type
The two (2) types of Cascade control are listed below:
Efficiency Optimization
This method is used when it is desired to have the most
efficient system. When the first boiler reaches a certain rate
(default = 80%), it lowers its rate to 40% and turns on the
next boiler at 40%. The two (2) boilers then modulate at the
same rate. As the calculated load increases further and both
boilers ramp up to 80%, it lowers the rate of the first two (2)
boilers to 53% and brings the next boiler on at 53%. The
three (3) boilers then modulate together. As the calculated
load decreases, the boilers will reach a lower threshold
(default = 10%), at which time the last boiler (the third one
in this example) will turn off and the Cascade will increase
the rates of the remaining boilers to provide the equivalent
total output as before ((3 x 10%) / 2 = 15% in this example).
30
Parameter Name
(as shown on the LCD screen)
Min
Value
0
ENABLE
N/A
0
0
32
68
0
0
1
1
0
Disable
L/L: Lead/Lag
This method is used when it is desired to run the least number
of boilers as possible. When the first boiler reaches 100% and
calculated demand is still greater, the Cascade will bring on
boiler number two. At the same time the first boiler will reduce
its firing rate by an amount equal to the initial firing rate of the
second boiler. As the calculated demand continues to increase,
the first boiler will go to high fire, followed by ramping up the
second boiler. If the calculated demand is still increasing once
the second boiler reaches 100%, the Cascade will bring on boiler
number three and reduce the firing rate of boiler number two
by an amount equal to the initial firing rate of the third boiler.
This sequence will continue until the load is matched or all
boilers are firing at 100%. When the load begins to decrease, the
last boiler to fire will modulate down to low fire and hold there.
As the calculated demand continues to decrease, the second
to the last boiler will modulate down to low fire. If calculated
demand is still decreasing, the last boiler will shut down and
the next to the last boiler will increase its firing rate to make
up the lost BTU's of the last boiler. If the calculated demand
continues to decrease, it will modulate down to low fire and hold
there while the next previous boiler starts to modulate down, as
before. This will continue until either demand is matched or all
boilers have shut down.
Cascade Set point Offset
This parameter determines how much the temperature can go
above set point before the lead boiler will turn off.
Cascade Set point Differential
This parameter determines how much the temperature must go
below the turn off temperature (Set point + Offset) before the
lead boiler turns on.
Service Manual
Max
Default
Value
Value
7
1
DISABLE
DISABLE
N/A
N/A
40
10
72
20
185
185
260
185
4:15
60
4:15
60
100
80
100
10
255
0
Enable
Disable
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