Siemens RDG20 KN Series Basic Documentation page 90

Functions
4
Control sequences
4.7.7.1 4-pipe application with PICV and 6-port control ball
Principle
90 | 180
valve as changeover (RDG26..KN)
In a 4-pipe fan coil application with DC 0...10 V fan control, the RDG26..KN
controls a combi valve (PICV) in combination with a 6-port ball valve as
changeover.
Note: Set DIP# 1 & 4 to ON (4-pipe with 6-port ball valve as changeover and PICV).
This application is used in 4-pipe systems with heat exchanger and differential
pressure controller (using a PICV).
The changeover signal DC 0...10 V controls the flow rate in the PICV, while the 6-
port ball valve, connected to the relay outputs, is used as changeover to switch the
sequence between heating and cooling.
Enable the flow limitation function (for PICV) via parameter P256 to balance
heating and cooling and avoid hydraulic problems caused by the different flow
rates. (see Additional functions [➙ 47]).
The fan can only be set on DC Y50 output in this application.
Set fan operation (P350) to enable (enable by default).
T[℃] Room temperature
W Room temperature setpoint
Control command "Valve"
YC
(cooling)
See Chilled/heated ceiling with pressure independent combi valve (PICV) and 6-
port ball valve for changeover (RDG26..KN) [➙ 95] for detailed information on how
the thermostat limits the mix of the heating and cooling medium as well as control
outputs.
The connection diagram for 4-pipe applications with PICV and 6-port ball valve as
changeover is available in Connection diagrams [➙ 156].
Y10 DC 0...10 V signal
Control command "Valve"
YH
(heating)
Flow limitation function for
P256
heating only
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