Technical Instructions
RCU50U and RCU50.2U Room Temperature Controllers
Document Number 155-327P25
for CAV Systems
Rev. 1, March, 2002
Page 2
Siemens Building Technologies, Inc.
Ordering
The temperature sensor, changeover mounting kit, and valve and damper actuators
must be ordered separately.
Table 2. Equipment Combinations.
Product Number
Description Technical
Instructions
QAH11.1 Temperature
sensor
155-329P25
GDE16…
44 lb-in NSR Air damper actuator
GLB16…
88 lb-in NSR Air damper actuator
155-187P25
SSB61U Valve
actuator
155-192P25
SSC61U
SSC61.5U
Valve actuator
155-313P25
SQS65U
SQS65.5U
Valve actuator
155-190P25
Function
The controller measures the room temperature with its integrated sensor and maintains
the set point by delivering 0 to10 Vdc control commands. The RCU50U and RCU50.2U
provide P-control. With the RCU50U, the proportional band can be 2°F or 7°F (1°C or
4°C) in heating mode and 1°F or 3.5°F (0.5°C or 2°C) in cooling mode (selectable with
DIP Switch No. 4). With the RCU50.2U, the proportional band is fixed, 7°F (4°C) in
heating mode and 3.5°F (2°C) in cooling mode.
•
RCU50U – When in the heating mode, on increase in temperature, the output signal
goes down (Reverse Acting - R.A.) from 10 to 0 volts. When in cooling mode, on
increase in temperature, the output signal goes up (Direct Acting - D.A.) from 0 to 10
volts.
•
RCU50.2U – The output signal can be reversed 0 to 10 or 10 to 0 volts via the DIP
switch.
Heating-Cooling with
Minimum Limitation
Cooling
TH0577R1
T [˚F]
XpK
XpH
W
Y10 [%]
Y10 [%]
100
0
100
c/o
VR
T Room
temperature
Y10 Output
percentage
W
Room temperature set point
XpH Proportional band heating
XpK Proportional band cooling
VR
0 to 100% minimum limitation of
cooling
output
c/o Changeover
Figure 1. RCU50U Function Diagram.
Heating-Cooling
TH0578R1
T [˚F]
XpK
XpH
W
Y10 [%]
Y10 [%]
100
0
0
100
c/o
T Room
temperature
Y10 Output
percentage
W
Room temperature set point
XpH Proportional band heating
XpK Proportional band cooling
c/o Changeover
Figure 2. RCU50.2U Function Diagram.
Minimum Limitation of
Cooling Signal
RCU50U
Using the potentiometer located on the circuit board, the cooling signal output can be
limited to a minimum value of between 0 and 100%. This can be used to ensure a
minimum supply air volume. When used in connection with a VAV controller, this
setting must be taken into account. To set minimum limitation, use a screwdriver to
adjust the potentiometer (see Figure 3). Values on the scale are percentage of full
operation.
