User Manual

Siemens Building Technologies Application :74 RWD68/74 - 02.2001

HVAC Products RWD68 1

RWD68/74

RWD68 Universal Controller

Application 74

Compensation shift

Room temperature control

Chilled water control valve

Two speed fan

Control (P or PI)

Room temperature control

Proportional control ( 0..10Vdc ) of the chilled water valve.

Digital output to energise second stage of supply fan

Outside air compensation of the supply air temperature set point.

Optional day / night set point adjustment .

........RWD68.......

RWD68/73

Room temperature sensor

Outside air temperature sensor.

Time clock or switch

2-port chilled water valve

Fan speed contactor.

Personal computer

Universal analogue input - main sensor

Auxiliary analogue input

Digital input

Analogue output

Digital output

Communication port

100%50%

• Room temperature sensor can be selected as Ni1000, Pt1000, or active sensor.

• Adjustable differential of digital output Q1.

• Adjustable proportional band of analogue output Y1.

• Integral action function selection and adjustment for output Y1.

• 24Vac controller supply voltage

• 0..10Vdc modulating control valve

• Outside air temperature sensor can be selected as Ni1000, Pt1000, or active sensor.

• Outside air compensation of the supply air temperature set point.

• Day / night set points can be selected via time clock or switch.

• Independent mode for the two cooling outputs, meaning that the digital output on and

off settings are set outside the analogue output proportional band.

Supplemental features

Control

Operating modes

PAGE 1
RWD68/74 RWD68 Universal Controller Application 74 Compensation shift Room temperature control Chilled water control valve Two speed fan Control (P or PI) Room temperature control Proportional control ( 0..10Vdc ) of the chilled water valve. Digital output to energise second stage of supply fan Outside air compensation of the supply air temperature set point. X1 X2 S1 Y1 Q1 PC RWD68/73 Optional day / night set point adjustment . Room temperature sensor Outside air temperature sensor.
PAGE 2
Description of operation 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.
PAGE 3
Main Display The main display shows , a) Whether Q1 is On or Off ( = off, = on ) b) Y1 output in Volts dc. (0..10V = 0..100% range) c) Whether day or night set point is selected. (¤ = day, b = night) d) X1 value ( room temperature) in ° C. Other displays are available by pressing the + button, and the various displays are listed below in sequence from the main display.