Combustion Management System; Check Functioning Safety Valves - Viessmann Vitocrossal 300 Service Manual

Service

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
2
O
Air factor λ
1.20
1.24
1.27
1.30
1.34
1.37
1.40
1.44
1.48
The Vitocrossal 300 CU3A boilers come equipped with Lambda Pro, the industry's first intelligent combustion
management system.
Check Functioning of Safety Valves
26
content or the
2
content
content (%) CO content (%) for natural gas
2 2
3.8
4.4
4.9
5.3
5.7
6.1
6.5
6.9
7.3
Vitocrossal 300 CU3A 26 to 57 Service
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.
CO
9.6
9.2
9.0
8.7
8.5
8.3
8.1
7.8
7.6
Ensure proper operation of low water cut-off(s)
(if applicable), pressure relief valve, and pump(s).
Check pressure gage, air vent and pressure relief valve.
Ensure that pressure relief valve does not leak and that
it operates in accordance with information provided by
the manufacturer.
Refer to maintenance instructions supplied
with low water cut-offs, pumps, etc.
Flush float water type low water cut-offs (if used).
Follow local regulations with respect to backflow
preventers.
If oil-lubricated pumps are used, ensure proper lubrication.
If motorized zone valves are used, refer to maintenance
instructions provided with zone valves.
or O content and air
2 2
content (%) for liquid propane gas
2
11.3
10.9
10.6
10.3
10.0
9.8
9.6
9.3
9.0