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Building Technologies Division User Manual LMS14... CC1U7471en
6 The settings in detail 07.05.2014
Flue gas temperature supervision is classified as non-safety-related and overrides
control of the boiler. If the flue gas temperature exceeds the lowest threshold (Flue gas
temp output limit (2478)), boiler output limitation becomes active. If the flue gas
temperature continues to rise, the boiler’s output is further limited – in a linear manner
to the flue gas temperature. Output limitation is conceived such that only minimum
output is delivered if the flue gas temperature reaches the next threshold (Flue gas
temp output red (2473)).
If the flue gas temperature exceeds that threshold as well, boiler output will be limited to
the minimum. If, in spite of output reduction, the flue gas temperature continues to rise,
reaching the switch-off threshold (Flue gas temp swi-off limit (2474)), the boiler is shut
down. Depending on the parameter setting (Flue gas superv shutdown (2476)), start
prevention takes effect for at least 10 minutes (Flue gas superv st prev tme (2477)) or
the LMS14… goes to lockout. The boiler is released again only when the flue gas
temperature has dropped.
The Output limitation function can be deactivated. For that, the output limitation
threshold (Flue gas temp output limit (2478)) must be set to OSV (---).
The Output limitation function provides P-control. To attenuate possible control
oscillations, an additional PT1 filter can be activated. This filter dampens falling flue gas
temperatures, but has no impact on rising flue gas temperatures. It can be activated by
*setting the filter time constant (Fl’g superv time con rel mod (2479)) to a value >0.
Function
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