Basic Documentation

74/256
Siemens Modular Heating Controller RMH760B CE1P3133en
Building Technologies 6 Boiler temperature control 2017-09-29
When the demand for heat is small, the basic stage cycles. When the demand for heat
increases, the 3-position output or a DC 0…10 V output is used to control the
combustion air damper.
At the same time, the amount of fuel supplied will also be increased, typically via an
additional switch on the air damper, or by simultaneous control of the amount of fuel
(gas / air ratio).
2526z02
P M BV OH Q...
z
LK
SA
M
Basic design of a forced draft burner
BV
Fuel valve(s)
ACC
Combustion air damper, fixed or motorized
M
Fan
OH
Oil preheater; located between nozzle and adjustable head with small light-oil burners, separate unit in the
case of large heavy-oil burners
P
Oil pump, coupled to fan motor
Q…
Flame detector
SA
Electromotoric air damper actuator
Z
Ignition transformer
The functioning with regard to activation and deactivation of the basic stage
corresponds to that of 2-stage burner operation. Release of modulation is analogous to
the release of the second stage.
The parameters used for the release and reset integral are the same as those used for
the 2-stage burner. Compared to the 2-stage burner, the release integral should be
selected smaller however (because in this case, it is not the entire capacity of stage 2
that is switched on, but only the modulating part that is released), and the reset integral
can be selected greater.
Release integral stage 2 or modulation: 10 K×m
Reset integral stage 2 or modulation 20 K×m
Locking time stage 2 or modulation 10 min
The locking time of stage 2 or modulation must be matched to the type of burner.
This ensures that the burner will always run in its basic stage for a minimum period of
time.
On burner startup and release of the basic stage, the controller drives the damper
actuator towards the fully closed position for a certain period of time. This ensures that,
after the burner startup sequence (prepurging, ignition, stabilization of flame, etc.), the
damper actuator will be driven to the start position so that only the basic stage will be
used for heating.
Deactivation or locking of modulation occurs at the same moment in time as the change
from the basic stage to cycling operation. If not yet done, the controller will again drive
the damper actuator to the fully closed position.
Recommended values for
modulating burners