Page 1
RAB20 Series
Two-pipe Fan Coil Room
Thermostat with Automatic
Changeover
Technical Instructions
Document No. 155-526P25
ET RAB-2
March 2, 2007
RAB20.1
Description
Features
Application
Two-wire, gas diaphragm-based fan coil room thermostat for heating or cooling
systems with two-pipe fan coil applications.
•
Automatic changeover
•
Manual, three-speed fan switch
•
Fan release function
•
Dual setpoint temperature scale
•
Two-point control algorithm (On/Off)
•
24 to120 Vac, 277 Vac operating voltage
•
Two mounting styles: electrical wall box or drywall
•
Wall plate adapter (ARG70) included with electrical wall box mount styles
The RAB20… is used in heating or cooling systems with external automatic
changeover devices (aquastats) to maintain the selected room temperature.
Typically used in commercial, high-rise and light industrial buildings in conjunction with:
•
Zone valves
•
Thermal valves
• Fans
•
Aqua sensors (changeover sensors, provided by others)
Product Numbers
Accessory
Technical Design
See Table 1.
ARG70 Wall box adapter
The RAB20… fan coil room thermostat is based on a two-wire, gas diaphragm
technology.
Siemens Building Technologies, Inc.
Page 2
Technical Instructions RAB20 Series Two-pipe Fan Coil Room Thermostat
Document Number 155-526P25
March 2, 2007
Operation
Heating Mode
Cooling Mode
Fan Speed
Fan Release Setting
Ventilation
Changeover
If the room temperature falls below the selected setpoint, the heating contact is closed.
If the room temperature rises over the selected setpoint, the cooling contact is closed.
The fan control speed can be controlled two ways:
• Manually, using the three-speed fan switch on the thermostat cover for continuous
operation.
(Low), (Medium), (High).
• Automatically, by switching to the selected fan speed using the thermostat for
controlled operation. Prior to commissioning, the jumper position corresponding to
the thermostat function must be selected.
There are three jumper position choices on the printed circuit board:
SR1
SR2
SR3
Auto
Auto
When the ventilation function (
Select fan speed as continuous operation
Fan is switched with the cooling valve
Fan is switched with the heating valve
) is selected (on the RAB20.1.. only), the heating and
cooling contacts are always open and the fan works at the selected speed.
Heating/cooling changeover is automatic, based on room temperature. Changeover is
achieved externally using an SPDT aqua sensor (not included) wired between
Terminals W, Y and the zone valve to change switch action.
Adjustments
The required temperature can be selected by a rotating setpoint adjuster on the front of
the thermostat.
High and low setpoint limit stops can be engaged to limit temperature range.
Table 1. Product Numbers.
Mounting Style Product
Description
Number
Electrical Wall
Box (with wall
box adapter)
RAB20UW
RAB20.1UW
Heating or cooling; degrees Fahrenheit and
Celsius; two-pipe auto changeover
Heating or cooling; degrees Fahrenheit and
Celsius; two-pipe auto changeover; fan only
function
Drywall
RAB20U
Heating or cooling; degrees Fahrenheit and
Celsius; two-pipe auto changeover
RAB20.1U
Heating or cooling; degrees Fahrenheit and
Celsius; two-pipe auto changeover; fan only
function
Page 2 Siemens Building Technologies, Inc.
Page 3
RAB20 Series Two-pipe Fan Coil Room Thermostat Technical Instructions
Document Number 155-526P25
March 2, 2007
Warning/Caution Notations
WARNING:
Specifications
Ambient Conditions
Wiring
Housing
Agency Certification
Operating voltage 24 to 120 Vac, 277 Vac
Frequency 50/60 Hz
Setpoint adjustment range 50°F to 85°F (10°C to 30°C)
Setpoint limit stops Adjustable
Switching differential (SD) ≤1.8°F (1°C), fixed
Switch rating 6A RES, 3.5A FLA, 12A LRA
Switch action Single-Pole, Double-Throw (SPDT)
Output 2-position (On/Off)
Weight 5 oz. (0.14 kg)
Dimensions 3.80 × 4.45 × 1.68 inches
(96.4 × 113.1 × 42.8 mm)
Color Ivory white with gray selector knobs
Operation
Temperature 32°F to 122°F (0°C to 50°C)
Relative humidity <95%
Transport/Storage
Temperature –4°F to 122°F (–20°C to 50°C)
Relative humidity <95%
Screw terminals for wires of 2 × 16 AWG
or 1 × 14 AWG
minimum 20 AWG
Material Plastic
Enclosure rating NEMA1
Bellows Environmentally-friendly gas
Conforms to CE requirements
UL listed to 873 (E35918)
cUL listed to Canadian standard
C22.2 No. 24-93
Personal injury, or loss of life may occur if you do
not perform a procedure as specified.
Part Number Description Technical Instructions
SFA71U 24V NC
SFA11U 120V NC
SFA208V/25 208V NC
SFA277V/25 277V NC
FTA71 24V NC 155-109
599 Series Zone
Valves
Siemens Building Technologies, Inc. Page 3
Table 2. Control Valves.
Two-way
Three-way
155-521
155-320P25
Page 4
Technical Instructions RAB20 Series Two-pipe Fan Coil Room Thermostat
Document Number 155-526P25
March 2, 2007
Mounting
Locate the unit where the air temperature can be sensed as accurately as possible. Do
not mount in direct sunlight or near other heat or refrigeration sources.
Mounting height is approximately 60 inches (1.5 m) above the floor.
The unit can be fitted to most commercially available recessed conduit boxes or directly
on the wall.
Figure 1. Recommended Mounting Locations.
(Dimensions in Inches)
WARNING:
1. This unit can be installed by authorized personnel only.
2. The unit must be de-energized and the operating voltage checked
before opening.
Installation
Required Tools
Setpoint Limit Stops
Adjustment
•
An ARG70 wall plate adapter (provided with electrical wall box mount models) must
be used to mount to a 2 × 4-inch or 4 × 4-inch electrical wall box.
•
An ARG70 wall plate adapter must be used to meet UL and cUL requirements.
•
The thermostat must be mounted on a flat wall.
•
All local electrical regulations must be complied with.
•
If there are thermostatic radiator valves in the reference room, set them to their fully
open position.
•
Small, flat-blade screwdriver
•
1/4-inch drill bit
•
Drill motor
•
Small mallet
• Pencil
To set limit stops, remove gray tabs located on the setpoint knob and position high and
low stops around the perimeter of knob as required. Each position on the setpoint dial is
1.8°F (1°C). See Figure 2.
Page 4 Siemens Building Technologies, Inc.
Page 5
RAB20 Series Two-pipe Fan Coil Room Thermostat Technical Instructions
Document Number 155-526P25
March 2, 2007
Drywall Mounting
1. Loosen the two screws at the bottom of thermostat.
2. Lift the bottom of the thermostat cover from the thermostat base and push up to
remove cover.
3. Remove sub-base from back of thermostat.
4. Using the sub-base (packed with thermostat) as a template, mark the hole locations
with a pencil.
5. Drill two 1/4-inch diameter holes for plastic wall anchors (provided).
6. Using a mallet, tap in the plastic wall anchors flush with wall.
7. Pull the wiring through the opening in the upper portion of the sub-base.
8. Level mounting plate.
9. Using the two wood screws provided, fasten sub-base to wall. Thermostat is not
position sensitive.
10. Pull the wiring through the sub-base.
11. Position thermostat housing over the two mounting lugs located at the top of the
sub-base and press down on cover until bottom lugs snap in place .
12. Terminate wires per wiring instructions on the inside of thermostat cover.
Optional: To set limit stops, remove gray tabs located on the setpoint knob and
position high and low stops around perimeter of knob as required. See Figure 2.
65
70
20
TH0625R1
60
15
55
10
50
L
a
n
d
i
s
&
75
20
18
22
25
16
24
14
26
12
10
8
S
t
a
e
80
28
30
85ºF
30
Cº
f
a
Figure 2. Setpoint Limit Stops.
13. Place all thermostat switches in the “down” position to allow cover switch sliders to
fit over the switches.
14. Insert the top of the thermostat cover into the slots located on the top of the
thermostat and press down.
15. Tighten the two screws at the bottom of the thermostat.
16. Return selector switches to the normal position. Adjust setpoint dial to desired
setting.
The installation is now complete.
Siemens Building Technologies, Inc. Page 5
Page 6
Technical Instructions RAB20 Series Two-pipe Fan Coil Room Thermostat
Document Number 155-526P25
March 2, 2007
4 × 4-inch Electrical Wall
Box Mounting
An ARG70 wall plate adapter (provided with electrical wall box mount models) is
required to mount an RAB… thermostat to a 4 × 4-inch electrical wall box.
1. Loosen the two screws at the bottom of thermostat.
2. Lift the bottom of the thermostat cover from the thermostat base and push up to
remove cover.
3. Using the four screws provided, fasten wall box adapter (3) to plaster ring (2),
supplied by others.
4. Pull wires through plaster ring (2).
5. Flex adapter mask (4) and snap in place inside wall box adapter (3).
6. Fasten sub-base (5), included with thermostat, to wall box adapter assembly (3)
and (4) with the two screws provided.
7. Follow Drywall Mounting Steps 7 through 16.
The installation is now complete.
TH0634R1
1
2
3
4
5
6
7
Figure 3. 4 × 4-inch Electrical Wall Box Installation.
1 Electrical wall box
2 Plaster ring
3 Wall box adapter *
5 Sub-base
6 Thermostat base
7 Thermostat cover
4 Adapter mask *
* Included with ARG70
Page 6 Siemens Building Technologies, Inc.
Page 7
RAB20 Series Two-pipe Fan Coil Room Thermostat Technical Instructions
Document Number 155-526P25
March 2, 2007
2 × 4-inch Electrical Wall
Box Mounting
An ARG70 wall plate adapter (provided with electrical wall box mount models) is
required to mount an RAB… thermostat to a 2 × 4-inch electrical wall box.
1. Loosen the two screws at the bottom of thermostat.
2. Lift the bottom of the thermostat cover from the thermostat base and push up to
remove cover.
3. Using the two screws provided, fasten wall box adapter (3) to plaster ring (2),
supplied by others.
4. Pull wires through plaster ring (2).
5. Flex adapter mask (4) and snap in place inside wall box adapter (3).
6. Fasten sub-base (5), included with thermostat, to wall box adapter assembly (3)
and (4) with the two screws provided.
7. Follow Drywall Mounting Steps 7 through 16.
The installation is now complete.
TH0635R1
1
3
4
5
6
7
Figure 4. 2 × 4-inch Electrical Wall Box Installation.
1 Electrical wall box
3 Wall box adapter *
4 Adapter mask *
5 Sub-base
6 Thermostat base
7 Thermostat cover
* Included with ARG70
Siemens Building Technologies, Inc. Page 7
Page 8
Technical Instructions RAB20 Series Two-pipe Fan Coil Room Thermostat
Document Number 155-526P25
March 2, 2007
Maintenance
Diagrams
The room thermostat is completely maintenance-free. If inoperable, replace entire unit.
WARNING:
High voltage. Disconnect power before servicing. Metal part is not
grounded.
AS Aqua sensor (by others)
L
G1 Control output fan speed I
(Low)
L
G2 Control output fan speed II
(Medium)
Y
M1
W
AS
N1
G3 Control output fan speed III
(High)
L Operating voltage
M1 3-speed fan
ZV
N Neutral
N1 Room thermostat
N
TH0508R3
G2G1
I II III
G3
W Valve output, heating
Y Valve output, cooling
ZV Zone valve
Figure 5. Wiring.
W
ON
OFF
TH0488R3
Heating Mode
SD
Y
ON
SP
T[˚F]
OFF
TH0489R2
SP
SD
Cooling Mode
Figure 6. Operating.
SD Switching differential
SP Room temperature
setpoint
T Room temperature
W Valve output signal
T[˚F]
heating
Y Valve output signal
cooling
Page 8 Siemens Building Technologies, Inc.
Page 9
RAB20 Series Two-pipe Fan Coil Room Thermostat Technical Instructions
Document Number 155-526P25
March 2, 2007
Dimensions
Dimensions in inches
(millimeters)
2.56 (65)
1.97 (50)
Ø 0.25 (6.4)
Ø 0.14 (3.6)
TH0495R2
4.45
(113.1)
3.80
(96.4)
Figure 7. RAB20… Unit.
1.68
(42.8)
0.51 (13)
2.56
(65)
0.51
(13)
TH0496R2
1.00
(25.5)
0.66
(16.9)
1.18
(30)
3.38
(86)
Figure 8. Base Plate.
1.38
1.18
0.46
(35)
3.9
(30)
(11.8)
(99)
4.21(107)
1.17(29.6) 1.1(28)
4.21(107)
1.64(41.75)1.64(41.75)
0.91(23)0.91(23)
4.72(120)
0.91(23) 0.91(23)
1.1(28)1.1(28)
4.72(120)
TH0512R1
Information in this publication is based on current specifications. The company reserves the right to make changes in specifications and models as
design improvements are introduced. Other product or company names mentioned herein may be the trademarks of their respective owners.
© 2007 Siemens Building Technologies, Inc.
Siemens Building Technologies, Inc.
1000 Deerfield Parkway
Buffalo Grove, IL 60089-4513
U.S.A.
0.33(8.5)
3.29(83.5)
TH0513R1
Figure 9. ARG70.
Your feedback is important to us. If you have
comments about this document, please send them to
SBT_technical.editor.us.sbt@siemens.com
1.1(28)1.1(28)
1.18(30)1.18(30)
Document No. 155-526P25
Country of Origin: US
0.04(1)
Page 9
Loading...