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Siemens Building Technologies Basic Documentation LMV51... CC1P7550en
HVAC Products 4 Burner control 01.10.2003
a) Normal start
With normal start, the fan will be deactivated also when there is a new demand for heat
in Phase 78 or when changing the type of fuel.
b) Direct start
When there is demand for heat in Phase 78, there will be a direct change to startup 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 air pressure switch’s OFF position in standby.
For this reason, the PS 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
functional check of the air pressure switch.
Parameter: NormDirectStart (NormalStart / DirectStart)
For both variants, following applies:
If, during postpurging, there is another demand for heat, or if demand for heat is still
present like in the case of type-of-fuel change, for example, that part of postpurging will
be stopped in Phase 78 in order to accelerate the following startup sequence.
In the case of burners that could be damaged by return heat (e.g. several burners
operating on one combustion chamber), continuous purging can be activated. In that
case, the fan runs in all phases.
To enable the air pressure switch to be tested, a PS relieve valve is required. This
valve is controlled in Phase 21 on burner startup, causing the air pressure to fall, so
that the «Air pressure OFF signal» can be delivered.
Parameter: ContinuousPurge (activated / deactivated)
As a response to extraneous light in the standby phase, it is possible to choose start
prevention or lockout.
Parameter: ReacExtranLight (Lockout / Startblock)
Normal / direct start
Continuous fan operation
Response to extraneous
light in standby
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