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Siemens Building Technologies CC1N7865en
HVAC Products 20.11.2002
Function
The RWF40... provides the following functions:
- One digital PID controller with a 3-position or analog output (optional)
- To control 2-stage burners, the RWF40... can be switched over to provide 2-
position control
- Automatic thermostat (or pressurestat) function in low-fire operation
- One shift controller for weather-dependent setpoint shifting
- One minimum limiter and one maximum limiter for the boiler temperature or the
boiler pressure
- One limit thermostat to DIN 3440 (output 1)
- One potential-free configurable contact
- Manual operating mode
- Communication via serial port (option)
- Self-setting function
W
3 analog inputs
2 binary inputs
Power supply
Serial port (optional)
Release of burner
Floating output
Limit comparator
Analog output (optional)
Power supply measuring transducer
RWF40...
7865f01e/1102
Input 1:
Actual value
for Pt100, Ni100,
Landis & Staefe Pt1000,
LG-Ni1000,
thermocouples
or standard signals
Input 2:
External setpoint,
setpoint shifting
for 0...1 k resistor
or linearized
standard signals
Input 3:
Outside temperature
for Landis & Staefa Pt1000,
LG-Ni1000
For potential-free
contacts
Input 1:
Operating mode changeover
Input 2:
Setpoint shifting /
changeover
Output 1:
- Relay (N.O. contact)
Output 2:
-Relay (controlling element open)
Output 3:
- Relay (controlling element closed)
Output 4:
- Relay (N.O. contact)
DC 24 V, 30 mA
(short-circuit proof)
Output 5:
Analog output
DC 0...10 V, DC 0...20 mA,
DC 4...20 mA
RS-485
MOD bus protocol
AC 100 ...240 V,
±10 %, 48...63 Hz
Function of the controller when used for burner control
In low-fire operation, the RWF40... operates like a control thermostat or pressurestat.
This means that it operates as a 2-position controller maintaining the required setpoint
by switching the burner on and off. The switching differential for 2-position operation
can be adjusted within a wide range. If the demand for heat increases, the controller
switches to high-fire operation only when an adjustable limit is exceeded. This function
is aimed at optimizing the burner´s switching ratio.
In that case, the RWF40... operates as a 2-position controller with adjustable switching
thresholds. Using the relays of the 3-position output, the RWF40... drives the actuator
to the 1
st
and 2
nd
output stage. In this operating mode, the optional analog output
switches between the minimum signal for the 1
st
stage and the maximum output signal
for the 2
nd
stage.
Block structure
Low-fire operation
High-fire operation, 2-
stage control
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