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Based on the system temperature (T_System) and the requested Cascade_Setpoint the managing water heater
calculates a required water heater setpoint, to achieve the requested Cascade_Setpoint.
The managing water heater provides the calculated setpoint to all dependent water heaters. The modulating
power of the dependent water heaters is PID controlled based on the calculated setpoint and the measured sys-
tem temperature.
Cascade HW setpoint adaption
When the system temperature is not high enough the setpoint for all water heaters will be adjusted.
The water heater setpoint will be increased when the system temperature drops below Cascade_Setpoint and
decreased when it rises above Cascade_Setpoint temperature.
Water heater input Rates
A cascade system operates most effective and efficiently when all of the water heaters in the system are the
same type. (so all EFW 85 e.g.)
17.3.4
C
ASCADE
In case a water heater is set as depending (Parameter 184, Address = 2-8/16) the DHW setpoint is always pro-
vided by the managing water heater, the internal control of the setpoint functions are disabled.
SET parameter 35 to Mode 0 on depending boilers only, "Menu-Settings-Boiler Settings-Boiler Parameters- Pa-
rameter "35 DHW Mode" This causes a crossed-out tap symbol at the normal display. If this setting is forgotten
the message MN: DHW Sensor Open appears.
C
17.3.5
ASCADE
Several different power control modes can be selected to operate the cascade system.
• Power mode 0:
Power control disabled, each water heater modulates based on the system setpoint.
• Power mode 1:
Power control algorithm to have a minimum amount of water heaters active.
• Power mode 2:
Power control algorithm to have a maximum amount of water heaters active.
• Power mode 3:
Power control algorithm to have a balanced amount of water heaters active.
Cascade – Water heater rotation
The water heater rotation function can change the start/stop sequence for the cascaded water heaters.
The parameter Module_Rotation_Interval sets the number of days after which the sequence is updated. When
Module_Rotation_Interval is set to 0, water heater rotation is disabled.
When the parameter Module_Rotation_Interval is updated the water heater rotation days left will be initialized
to the new Module_Rotation_Interval setting.
When for example Module_Rotation_Interval = 5, the start sequence is as following (x is the last water heater):
Days
Start/Stop sequence
Day 0-5
1-2-3-4-5-6..x
Day 5-10
2-3-4-5-6..x-1
Day 10-15
3-4-5-6..x-1-2
Day 15-20
4-5-6..x-1-2-3
Day 20-25
5-6..x-1-2-3-4
With parameter First_Module_To_Start the current water heater that is first to start in the sequence is selected.
When the water heaters are rotated the parameter First_Module_To_Start is automatically updated to the next
water heater. When water heater rotation is disabled the parameter First_Module_To_Start is reset to 0.
When the First_Module_To_Start is manually changed the control will clear all demand of the cascade control.
After this is will start cascade demand generation with the new selection for First_Module_To_Start
– D
W
EPENDING
ATER HEATER
– P
OWER BALANCE MODE
E93.1804.014
105
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