User Manual

Siemens Building Technologies Application :74 RWD68/74 - 02.2001
HVAC Products RWD68 2
The temperature sensor senses the room conditions and on a rise in temperature
the RWD68 via Y1 analogue output modulates the chilled water control valve as
determined by the cooling set point and proportional band settings.
When the chilled water valve is fully open, on a further increase in temperature
the Q1 digital output energises the fan speed contactor to switch the fan from
50% to 100% fan speed, as determined by the Q1 ON setting.
The O/A temperature sensor senses the outside air temperature, and adjusts the
supply air temperature set point as per the temperature shift program set up in
controller.
Cooling sequences
Y1
Q1
Load
Output
Voltage
OFF
ON
Y1-Setpoint
Min V
Max V
Cooling
XP
Cooling
Q1-Setpoint
Y1
G
Y1
S1
D1
GO
Y..
BM
X1 X2MM
3367A03
X1
M
M
GO
G
24 V SN
24 V SP
N1
TOOL
PC
Q12 Q14
Q11
Q1
FSC
G
BM
G
X2
Y1
RWD68
N1 RWD68 controller
X1 Main temperature sensor
X2 O/A temperature sensor.
S1 Time clock or switch
Q1 Potential-free relay contacts for on / off control
Y1 Valve actuator with 0..10Vdc input
FSC Fan speed contactor
PC Personal computer
Description of operation
Function diagram
Connection diagram