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Building Technologies
Boiler Sequence Controller RMK770
CE1P3132en
HVAC Products
9 Precontrol
01.03.2005
9.5.3
Heat demand transformers
The heat demand transformer described in chapter 8 “Heat demand and heat requisitions”
can be linked either to the primary controller or directly to the boiler sequence manager
(main distributor). The selection is made in
Extra configuration > Heat requisition [%]
When using setting heat requisition [%] on the “Primary controller”, the transformer is
linked to the primary controller. Per default, the transformer is linked to the main dis-
tributor.
9.6
Control of mixing valve
9.6.1 General
The thermal output of mixing valve control can be reduced by functions of a higher
priority (e.g. limitation of the return temperature) or by functions of other plant (boiler,
DHW heating) via load control.
The following mixing valve settings are valid for both 3-position and DC 0…10 V actua-
tors.
Main menu > Settings > Primary controller > Mixing circuit controller
Operating line
Range
Factory setting
Actuator run time
1…600 s
120 s
P-band Xp
1…100 K
40 K
Integral action time Tn
0…600 s
20 s
Locking signal gain
0…200 %
100%
For more detailed information about mixing valve control and its settings, refer to chap-
ter 5 “General functions, fundamentals”.
By using the locking signal gain, it is possible to predefine how intensely the primary
controller shall respond to load control signals.
9.6.2 Load
control
The primary controller can be influenced by load control signals of a heat source.
A load reduction can be triggered by one of the following functions:
•
Protective boiler startup
•
Minimum limitation of the boiler return temperature
The primary controller does not respond to locking signals triggered by DHW heating.
Load increase can be brought about in the form of pump or mixing valve overrun. In
that case, it is only a maintenance of load.
9.7
Setpoint boost mixing valve and system
pump
Typically, a mixing valve necessitates setpoint boost, enabling it to compensate for
boiler temperature fluctuations.
With system pumps, this setpoint boost is not a basic requirement for compensating
boiler temperature variations. However, in the case of long pipes between boilers and
consumers, heat losses on the way to the consumers can occur, depending on the
quality of pipe lagging, so that setpoint boost can be desirable in those situations also.
Load control
Note
Load reduction
Load increase