Technical Instructions
RDU20U, RDU50U and RDU50.2U Room Temperature Controllers
Document Number 155-735
with LCD for Heating and Cooling Systems
November 1, 2006
Page 8
Siemens Industry, Inc.
Engineering Notes
RDU50U with heating-cooling changeover input 2
–3 and
RDU20U with heating-cooling changeover input 7
–8:
•
In systems without automatic changeover, the temperature sensor can be replaced
by an external switch for manual changeover.
•
In systems with Heating only mode, do not connect a sensor to the control
ler’s input.
•
With Cooling only mode, the controller input must be bridged.
Mounting,
Installation and
Commissioning
Notes
•
Check the position of the DIP switches and change them, if necessary.
•
After applying power, the controller makes a reset, which takes approximately three
seconds; it is then ready to operate.
•
Mount the unit on a wall of the room to be heated or cooled. Do not mount in direct
sunlight or near other heat or refrigeration sources. (See Figure 11.)
•
Mounting height is approximately 60 inches (150 cm) above the floor.
(See Figure 11.)
•
The connecting wires can be run to the controller from a recessed conduit box.
Figure 11. Acceptable Mounting Locations.
•
Prior to fitting the changeover sensor on a pipe, thermal conductive paste must be
applied to the location on the pipe where the sensor is to be placed.
•
The cables used must satisfy the insulation requirements for 24 Vdc potential.
•
To access the wire terminal block, loosen the cover screw and open the plastic
cover. See Figure 12.
Figure 12. Accessing the Wire Terminal Block.
•
Sensor inputs 4
–3 and 2–3 (RDU50U and RDU50.2U) and 8–9 and 8–7 (RDU20U)
carry 24 Vdc potential. If the sensor's cables must be extended, they must be suited
for 24 Vdc voltage.
•
Complete installation instructions are included with the controller.
