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Building Technologies
Boiler Sequence Controller RMK770
CE1P3132en
HVAC Products
7 Boiler temperature control
01.03.2005
The terminals still available for selection are the free terminal pairs (Q1/Q2, Q3/Q4,
Q5/Q6) for the open and the close signal. Generally, special terminal pairs are required
for that purpose (RC units for radio interference suppression; for more detailed informa-
tion, refer to subsection 3.3.2 “Terminal assignment and properties of outputs”).
By selecting “Maint boiler return temp mod“, a mixing valve with DC 0…10 V output is
assigned. If required, this output can be matched to the type of mixing valve used.
Main menu > Commissioning > Settings > …
or
Main menu > Settings > Boiler … > Limitations
Operating line
Range
Factory setting
Boiler return temperature min
---- / 8…140 °C
---- °C
For adapting the control parameters to the type of plant (actuator and controlled sys-
tem), the same setting parameters as those used with the mixing heating circuit are
available.
For more detailed information, refer to section 5.7 “Mixing valve control”.
Main menu > Commissioning > Settings > …
or
Main menu > Settings > Boiler … > Return control
Operating line
Range
Factory setting
Actuator running time
1…600 s
120 s
P-band Xp
1…100 K
40 K
Integral action time Tn
0…600 s
40 K
If a minimum return temperature shall be ensured, it is necessary to select the minimum
boiler temperature accordingly. The minimum boiler temperature must be at least a few
K higher than the minimum return temperature.
In the case of plant with a mixing valve for the maintained boiler return temperature, the
mixing valve will be driven to the fully closed position if the return temperature sensor is
faulty and then deenergized to make possible manual adjustment.
If there is no return temperature sensor configured, a fault status message will appear.
If only a return temperature sensor is configured with no mixing valve present, the sen-
sor will be used for display purposes.
7.11 Flue gas temperature supervision
If the flue gas temperature shall be monitored, a sensor must be configured in the extra
configuration.
Main menu > Commissioning > Extra configuration > Boiler … > Inputs
Operating line
Adjustable values / remarks
Flue gas temperature sensor
Assign input
It is to be noted here that for the temperature inputs, a Ni1000 sensor is configured as
standard. However, for flue gas temperature measurements, Pt1000 sensors are often
used; for this reason, Pt1000 is set here as a default value. The type of sensor can be
adapted under
Settings > Inputs
at the configured terminal.
If a flue gas temperature sensor is configured, the following functions are available for
selection:
This function is active whenever a flue gas temperature sensor is selected.
Main menu > Boiler … > Inputs/Setpoints
Operating line
Adjustable values / remarks
Flue gas temperature maximum
Configuration of a pair of
terminals for a 3-position
mixing valve
Return temperature
setpoint
Fault of return tempera-
ture sensor
Slave pointer function