Shutdown; Home Run; Special Cases (Deviations) - Siemens LMU54 Series Basic Documentation

Shutdown

Home run

Special cases (deviations)

22/171
Siemens Building Technologies
HVAC Products
The change from the operating position to «Standby» is made when there is no more
demand for heat and is divided into «Shutdown» and «Home run».
«Shutdown» consists of postpurging, which can be deactivated.
With postpurging, there is a choice of 2 operating modes the difference being the way
the fan is controlled.
Parameterization choice 1:
• PH_THL2_1 (0.2 s): Change during postpurging, to the level of the last operating
command
• PH_TN1 (tn): Postpurging to the level of the last operating command
Parameterization choice 2:
• PH_THL2_2 (THL2): Change during postpurging, to the level of prepurging
• PH_TN2 (tn): Postpurging to the level of prepurging
The home run is used to bring about the change to the «Standby» position.
Normally, the home run is made on completion of «Shutdown».
After extraordinary events (refer to the sequence diagram), or in the case of a reset, the
home run brings the unit back to its basic position («Standby»).
In the case of a new demand for heat, the home run triggers a faster startup sequence.
This is accomplished by a shorter «TNN» followed by a direct change from the
«PH_TNN» phase to the «PH_THL1_1/2» phase. This means that the «Standby» state
will be skipped.
• PH_TNB (TNB): Permitted afterburn time
• PH_TLO (TLO): Permitted period of time with «LP» closed (if present) or speed >
«N_TL-N_TL_Delta»
• PH_TNN (TNN): Permitted period of time at speed > «NoG_Null»
• Forced prepurging: In the case of a reset after lockout and after power ON, forced
prepurging with the «LmodVOr» parameter is initiated, which takes place in the
«PH_TV» phase and which lasts 21 seconds, or «tv», if «tv» > 21 seconds.
The deviations marked with «Z» in the sequence diagram cause the burner control to
perform forced prepurging in the next startup phase.
• Repetition at the end of «TSA»: In the event no flame is established at the end of
«TSA», there is a choice of lockout or repetition can be triggered by changing to the
home run. The number of repetitions is limited and can be selected via the
«RepZaehler» parameter.
However, the general conditions of the different adjustable capacity ranges must be
observed (refer to the table further below).
• In the event of loss of flame during operation, the burner control initiates lockout or
changes to home run with restart, depending on the capacity range (refer to the table
further below)
• Prepurging: Can be deactivated by using the setting 0 seconds. In that case - as
shown on the sequence diagram - a change from the «PH_THL1_1» phase to the
«PH_TW1» phase will take place
• Preignition time: If parameter «tvz» is set to 0 (no ignition prior to «TSA»), the
«PH_TVZ» phase takes no more than 0.2 seconds (minimum time)
• Forced intermittent operation: After 24 hours of continuous operation at the latest,
forced intermittent operation is triggered, which ensures a regular shutdown to the
«PH_STANDBY» phase.
The timer for forced intermittent operation is reset in the «PH_STANDBY» phase.
Quick startup with forced intermittent operation is not possible.
Basic Documentation LMU54... / LMU64...
3 Functions
CC1P7494en
07.11.2002