Siemens LMV51 Series - Page 273

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Siemens Building Technologies Basic Documentation LMV5... CC1P7550en
HVAC Products 19 Addendum 4: LMV52... with O2 trim control and O2 module 13.08.2004
19.5 O2 monitor
The O
2 monitor can be used with or without O2 trim control. When O2 trim control is ac-
tivated, the O
2 monitor will automatically become active.
19.5.1 Delayed O2 min. value
Due to the long time it takes the flue gases to pass through the boiler’s flueways, the
O
2 value currently acquired is delayed compared to the residual oxygen content occur-
ring the same moment in the combustion chamber. To prevent O
2 min. values from be-
ing compared with “old“ O
2 values, the O2 min. values used by the O2 monitor are de-
layed by Tau as acquired during adaption, using a software timing element PT1.
19.5.2 Switch-off criteria
If
a) the actual O
2 value falls for > 3 seconds below the O2 min. value delayed via the
PT1 timing element, or
b) the actual O
2 value falls for > 3 seconds below the smallest parameterized O2 min.
value,
one of the following reactions takes place, depending on the operating mode:
Parameter: O2Ctrl/Guard (O2-guard / O2-control)
Safety shutdown will take place, followed by a repetition if possible, otherwise lockout.
Parameter: O2Ctrl/Guard (conAutoDeac)
O
2 trim control will automatically be deactivated and the system operates along the pa-
rameterized ratio curves. O
2 trim control must be manually reactivated.