Low-Fire Shutdown; Normal / Direct Start - Siemens LMV50 Series Manual

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4.2.3.9 Low-fire shutdown

To prevent the boiler from shutting down when operating at high-fire, the fuel-air ratio
control system first changes to low-fire when there is no more request for heat from the
controller. Only then do the valves close. The maximum time MaxTmeLowFire for
changing to low-fire operation can be parameterized. If the time is set to 0.2 seconds,
low-fire shutdown is deactivated.
Parameter MaxTmeLowFire

4.2.3.10 Normal / direct start

Normal start
With a normal start, the fan is also deactivated when there is a new request for heat in
phase 78 or when changing the type of fuel.
Direct start
there is a request for heat in phase 78, a direct change to startup is made via phase 79 to
phase 24 without switching the fan off, so that the startup sequence will be accelerated.
But this would suppress checking the OFF position of the air pressure switch in standby.
For this reason, the pressure switch relieve valve is controlled in phase 79. This valve
ensures that the air pressure switch is relieved of the pressure produced by the fan so
that it can signal Air pressure OFF although the fan motor is running, thus making
possible a function check of the air pressure switch.
For both variants, following applies:
If, during postpurging, there is another request for heat, or if the request for heat is still
present like in the case of type-of-fuel change, for example, that part of postpurging is
stopped in phase 78 to accelerate the directly following startup sequence.
Parameter NormDirectStart (NormalStart / DirectStart)
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CC1P7550en
22.05.2018