Functional Description; Combustion Management Systems - Viessmann VITODENS 200-W Service Instructions Manual

Vitodens 200-W B2HA 112, 150 Service

Functional Description

Space heating mode
The control unit calculates a boiler water setpoint
temperature based on the outdoor or room temperature
(where a room temperature dependent remote control is
connected) and on the slope/shift of the heating curve.
The computed boiler water setpoint temperature is
transmitted to the burner control unit.
From the boiler water setpoint and the actual temperature
the burner control calculates the degree of modulation
required, and regulates the burner accordingly. The
maximum operating boiler water temperature is limited in
the burner control unit to 165ºF (74ºC) by the electronic
temperature control. The maximum adjustable high limit
of the boiler is 180ºF (82ºC).
The fixed high limits of the safety chain interlock
the burner control unit at 210ºF (99ºC) boiler water
temperature.
Combustion Management System
The combustion management system utilizes the physical
correlation between the level of the ionization current
and the air factor λ. For all gas qualities, the maximum
ionization current results with air factor λ.
The ionization signal is evaluated by the combustion
management system, and the air factor is adjusted to
between λ=1.24 and 1.44. This range provides for an
optimum combustion quality. Thereafter, the electronic
gas valve regulates the required gas volume based on the
prevailing gas quality.
To check the combustion quality, the CO
O content of the flue gas is measured. The actual values
2
enable the prevailing air factor to be determined.
Air factor λ - CO 2 /O content
2
Air factor λ O content (%)
2
1.20 3.8
1.24 4.4
1.27 4.9
1.30 5.3
1.34 5.7
1.37 6.1
1.40 6.5
1.44 6.9
1.48 7.3
The Vitodens 200-W, B2HA boilers come equipped with Lambda Pro, the industry's first intelligent combustion
management system.
Domestic hot water supply with gas-fired space heating
boiler
Domestic hot water heating is activated when the tank
temperature is 4.5ºF (2.5ºC) below the tank temperature
setpoint value. The burner and the tank DHW pump are
switched on. In the factory default setting, the desired
boiler water temperature is set at 36ºF (20ºC) above
the tank temperature setpoint value. When the actual
tank temperature rises 4.5ºF (2.5ºC) above the tank
temperature setpoint value, the burner is switched off
and the time delay function of the tank DHW pump is
activated.
The temperature differential of 4.5ºF (2.5ºC) can be
adjusted in coding level 2, address "59" DHW boost
heating / additional heating function. This function
will heat your DHW tank to a second DHW setpoint
temperature within the fourth time phase. It can act as
an "Anti-Legionnaire-Function" if the DHW supply is not
heated to 140ºF (60ºC) during the regular time schedule.
You can activate this function by selecting a switching
period for the fourth time phase. (See Vitodens 200-W,
B2HA Operating Instructions.)
The temperature setpoint for this function is adjustable in
coding address "58".
The relationship between the CO
factor λ is illustrated in the table below.
To achieve an optimum combustion control, the system
regularly performs an automatic self-calibration; also after
a power failure (shutdown). For this, the combustion is
briefly regulated to max. ionization current (equals air factor
λ=1). The automatic calibration is performed shortly after
the burner starts and lasts approximately 5 seconds.
During the calibration, higher than normal CO emissions
may occur briefly.
content or the
2
CO content (%) for natural gas
2
9.6
9.2
9.0
8.7
8.5
8.3
8.1
7.8
7.6
Outdoor Reset Programming Unit
or O
2 2
CO content (%) for liquid propane gas
2
11.3
10.9
10.6
10.3
10.0
9.8
9.6
9.3
9.0
content and air
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