Viessmann VITODENS 200 Start-Up And Service Instructions page 15

Steps
(continued)
I S
nitial start-up ervice
outlet
X
Do not adjust screws X and Y!
7. How the Vitodens 200 boiler operates...
The MatriX burner blower and the combination gas valve are factory calibrated and
pre-adjusted for optimum boiler performance at all firing rates through a
non-mechanical, pneumatic modulating link between combustion air and gas flows.
Blower speed is automatically increased or decreased based on heat demand and
venting system resistances, thereby regulating the amount of combustion air
drawn. The pneumatic modulating link between air and gas introduces the required
amount of gas for correct combustion to meet the current heat demand, based on
a linear relationship between ∆ P air and ∆ P gas.
Optimum combustion air flow rate is recognized and monitored by the differential
air pressure sensor (transducer). The output voltage signal of the transducer is
analyzed for logic by the LGM 29.XX burner ignition control unit. The LGM 29.XX
unit contains pre-programmed performance curves and operational safety
parameters unique for every boiler model.
See page 47 for sequence of operation.
Flue gas adaptation function
The Vitodens employs a flue gas adaptation function. This unique function
records, processes, and reacts in real time to fluctuations in pressure drops in the
vent pipe during normal operation caused by partial pipe blockages due to ice
formation at the vent termination, debris and/or sudden high winds. Such increase
in pressure drop, if not promptly corrected, will reduce the combustion air flow
rate, and hence lead to unstable combustion. The differential air pressure sensor
(transducer) records such pressure drops and supplies voltage signals to the LGM
29.XX burner ignition control unit which, in turn (based on stored performance
curves and safety parameters), initiates prompt adjustment of the blower rotational
speed, thus readjusting the combustion air flow rate for optimum combustion. The
same automatic adaptation logic applies if combustion air is reduced (or increased)
due to slower (or faster) blower speed resulting from line voltage drops (or
increases) below (or above) the threshold of 85% (or 110%).
PE
Y
inlet
Initial Start-up and Service
WARNING
FOR FACTORY CALIBRATING
PURPOSES, THE COMBINATION GAS
VALVE IS EQUIPPED WITH
ADJUSTMENT SCREWS X AND Y.
DO NOT ATTEMPT TO ADJUST OR
READJUST THESE SCREWS.
ANY ATTEMPT TO TAMPER WITH
FACTORY PRE-ADJUSTED SETTINGS
WILL LEAD TO UNSTABLE OPERATION
AND WILL AFFECT BOILER
WARRANTY.
15