Siemens RDG20 KN Series Basic Documentation page 54

Functions
4
Additional functions
Note
Flow limitation function for
combi valve (PICV) (P256,
RDG26..KN)
Dewpoint monitoring
54 | 180
To enable this function, the multifunctional input, to which the supply air sensor is
connected, needs to be set to "Supply air sensor" (e.g., P150 = 9). Then the
parameters for the limits are displayed (P063: minimum supply air temperature,
P064: maximum supply air temperature).
●
This function is only active in Comfort mode when:
– Valve output type is 3-position (RDG20..KN) or DC 0...10 V (RDG26..KN)
– Electric heater is PWM / 3-position (RDG20..KN) or DC 0...10 V
(RDG26..KN)
●
This function can not be used for radiators.
●
This function can not be used in 4-pipe with 6-port ball valve application.
Set different limits to the flow in both sequences, heating and cooling to balance
heating and cooling systems and avoid hydraulic problems caused by the different
flow rates.
Cooling typically requires a higher flow rate than heating, and the combi valve
(PICV) is mechanically and manually set to the cooling flow limit.
However, when the system operates in heating mode, set another flow limitation.
The new limit to the DC 0...10 V signal (new 100 % heating demand) can now be
set with the parameter P256.
The function can be enabled on all combined heating/cooling applications with
DC 0...10 V output for universal and fan coil unit applications.
T[℃] Room temperature
Y10 DC 0...10 V signal
W Room temperature setpoint
The function can be enabled for the following heating/cooling applications with
DC 0...10 V output. P256 is not visible on other applications.
Fan coil type
● 2-pipe
● 2-pipe with electrical heater
● 2-pipe with radiator
● 2-pipe/2-stage
● 4-pipe
● 4-pipe with electrical heater
● 4-pipe/2-stage
●
4-pipe with PICV and 6-port ball
valve as changeover
Dewpoint monitoring is essential to prevent condensation on the chilled ceiling
(cooling with fan disabled, P350 = 0) and associated damages to the building.
A dewpoint sensor with a potential-free contact is connected to multifunctional
input X1, X2 or U1. If there is condensation, the cooling valve is fully closed until no
more condensation is detected, and the cooling output is disabled temporarily.
YH Control command "Valve"
(heating)
YC Control command "Valve"
(cooling)
Universal type
● Chilled/heated ceiling
● Chilled/heated ceiling and electric
heater
● Chilled/heated ceiling and radiator
●
2-stage chilled/heated ceiling
●
Chilled ceiling and radiator
●
2-stage chilled and heated ceiling
●
H/C ceiling with PICV and 6-port
ball valve as changeover
A6V11545892_en--_c