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Siemens Building Technologies Application :48 RWD68/48 - 02.2001

HVAC Products RWD68 1

RWD68/48

RWD68 Universal Controller

Application 48

Maximum priority

Room temperature control

Air electric heater

Chilled water control valve

Control (P or PI)

Room temperature control

On/off control of the air electric heater

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

Maximum priority function to control the cooling valve.

Optional day / night set point adjustment .

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

RWD68/48

CCV

HCV

HLT

Room temperature sensor

Input from humidity controller.

Day/Night selector

2-port chilled water valve

Humididty control valve

Personal computer

High limit thermostat

Pressure switch

Humidity controller

Humidity sensor

Universal analogue input - main sensor

Auxiliary analogue input

Digital input

Analogue output

Digital output

Communication port

HLT

HCV

• Room temperature sensor can be selected as Ni1000, Pt1000, or active sensor.(X1)

• Adjustable dead zone with separate heating and cooling set points.

• Adjustable differential of digital output Q1.

• Adjustable proportional band of analogue output Y1.

• Integral action function selection and adjustment.

• The cooling coil control valve is controlled by both the humidity controller and the

temperature controller via the priority function in the temperature controller.

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

• A high limit manual reset thermostat is mounted downstream of the air electric heater,

and de-energises the heater on excessive duct temperatures. This thermostat has to

be manually reset following detection of overheating. It is often supplied by the

supplier of the electric heater.

• A pressure switch is also specified to detect loss of static pressure in the duct,

indicating loss of fan. This also de-energises the electric heater but it is auto reset and

allows electric heater function following the detection of fan operation.

• These safety units can be connected directly in series with small electric heaters, but

for larger electric heaters they are connected to a heater contactor that switches the

electric heater.

Supplemental features

Control

Operating modes

Safety functions

Summary of content (3 pages)

PAGE 1
RWD68/48 RWD68 Universal Controller Application 48 Maximum priority Room temperature control Air electric heater Chilled water control valve Control (P or PI) Room temperature control On/off control of the air electric heater Proportional control ( 0..10Vdc ) of the chilled water valve. Maximum priority function to control the cooling valve. X1 X2 S1 CCV HCV PC HLT PS HC HS S1 M1 Y1 P Room temperature sensor Input from humidity controller.
PAGE 2
Description of operation The main temperature sensor senses the room conditions and on a fall in temperature the RWD68 via Q1 digital output switches the air electric heater on and off as determined by the heating set point and differential settings. On a rise in temperature the RWD68 via the Y1 analogue output modulates the chilled water valve as determined by the cooling set point and proportional band settings.
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.