Beckett RWF40 Instructions - Manual (Page 6)

6/10
Building Technologies CC1N7865en
HVAC Products 01.09.2005
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.
In that case, the RWF40... operates as a PID / PI controller with a 3-position output
without position feedback signals or, optionally, with a modulating output. By making
use of its self-setting facility, the RWF40... is able to determine the PID / PI control
parameters, or the parameters can be set manually.
Using a potential-free contact, the RWF40... can be switched from the modulating
mode to 2-stage operation.
In the case «setpoint shifting» is configured, the current setpoint is shifted by an adjust-
able amount. Configuration of «setpoint changeover» provides changeover between 2
setpoints adjusted on the RWF40... If analog input 2 is configured for an «external set-
point», changeover is provided between the setpoint adjusted on the RWF40... and an
external setpoint.
Potential-free contact «K6» can be assigned a number of functions.
Example: Limit value supervision
4 buttons on the unit front are used to operate and program the RWF40... During op-
eration and programming, the 7-segment displays show the parameter values and pa-
rameter names.
The controller´s standard configuration ex works is such that when connecting a
QAC22… outside sensor, automatic changeover to weather-dependent setpoint shifting
takes place.
The signal delivered by the QAC2... outside sensor must not be fed parallel to sev-
eral RWF40...!
Low-fire operation
High-fire operation,
2-stage control
High-fire operation,
modulating control
Binary input 1 (change-
over of operating mode)
Binary input 2 (setpoint
shifting or setpoint
changeover)
Limit comparator
Operation
Weather-dependent
setpoint shifting