Note!
The function cannot be selected in systems Anl 4, 5 and 9 with solar system and in system Anl 11 with VF3.
7.10 Flow rate/capacity limitation
Flow rate/capacity limitation can be implemented based on a pulse or standardized signal of 0/4 to 20 mA provided by the heat meter. This only applies in plants without solar system. Par- ticularly when a standardized signal is applied, a heat meter (flow meter) with high measuring accuracy is required.
It must be ensured that the controller is supplied with updated measured values in intervals of max. 5 seconds.
In system Anl 1, just the maximum limit for the flow rate or capacity can be entered.
7.10.1 Limitation using pulse input
A connected heat meter (terminals GND/15) with pulse output can be used to limit either the flow rate or the capacity in the system.
Two different maximum limits can be set: Maximum limit
Maximum limit for DHW exclusively for DHW heating
All limit values are given in the unit “pulses per hour“ [pulse/h]. As a result, the controller does not distinguish between a flow rate pulse signal or a capacity pulse signal. As the displayed cur- rent pulse rate P [pulse/h] is calculated depending on the interval between the received pulses, it is natural that the controller cannot react immediately to all rapid flow rate or capacity changes which occur in the system.
When the pulse rate reaches the current Max. limit, the current flow set point is reduced. How strongly the controller responds is determined by the Limiting factor.
In systems Anl 4 to 6 and 11, the control circuit with lowest set limit in the set point is always re- duced.
Example to determine the limit:
If a capacity of 30 kW is to be limited, the following limit value must be set for a heat meter with an output of one pulse per
30 kW
P =1 KWh / pulse = 30 pulse / h
EB 5476 EN 61
