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Vitocrossal 300 CU3A 26 to 199 Service
Check Functioning of Safety Valves
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.
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.
Refer to maintenance instructions supplied
with low water cut-offs, pumps, etc.
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
2
content or the
O
2
content of the flue gas is measured. The actual values
enable the prevailing air factor to be determined.
The relationship between the CO
2
or O
2
content and air
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.
The Vitocrossal 300 CU3A boilers come equipped with Lambda Pro, the industry’s first intelligent combustion
management system.
Air factor
λ
- CO2/O
2
content
Air factor
λ
O
2
content (%)
CO
2
content (%) for natural gas
CO
2
content (%) for liquid propane gas
1.20
3.8
9.6
11.3
1.24
4.4
9.2
10.9
1.27
4.9
9.0
10.6
1.30
5.3
8.7
10.3
1.34
5.7
8.5
10.0
1.37
6.1
8.3
9.8
1.40
6.5
8.1
9.6
1.44
6.9
7.8
9.3
1.48
7.3
7.6
9.0
Service