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Building Technologies
Modular Heating Controller RMH760B
CE1P3133en
HVAC Products
6 Boiler temperature control
05.02.2007
6.5.4
Control of modulating burners
Main menu > Commissioning > Settings > …
or
Main menu > Settings > Boiler > Burner modulating
Operating line
Range
Factory setting
Actuator run time
1…600 s
60 s
P-band Xp
1…200 K
20 K
Integral action time Tn
0…600 s
150 s
Derivative action time Tv
0…30 s
20 s
Modulating burners only modulate above a certain level. For standard forced draft
burners, this level is at about 30 to 40 % of the rated capacity.
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 combus-
tion 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).
25
26z
02
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 corre-
sponds 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
Recommended values for
modulating burners