Siemens LMU54 Series - Behavior in Different Operating Modes; Pump Overrun; Normal Operation (Heating Operation); Reduced (Setback) Operation

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Siemens Building Technologies Basic Documentation LMU54... / LMU64... CC1P7494en
HVAC Products 3 Functions 07.11.2002
Mandatory settings
No. DPA no. Parameter name Function Setting level
OEM Installer
9 174 NqmodNenn Speed at the design point Installer No Yes
10 175 NqmodMin
Minimum speed in heating
operation
Installer No If required
11 188 NqmodMinBw
Minimum speed in DHW
operation
Installer No If required
12 181 TkSnorm
Maximum boiler temperature
setpoint
Installer No Yes
13 173 TiAussenNorm
Design outside temperature
at the design point
Installer No Yes
14 172 dTkTrNenn Design differential Installer No Yes
15 116 dTkTrMax
Maximum temperature
differential of ∆T control
OEM Yes If required
167 KpDt Proportional coefficient OEM No If required
168 TvDt Derivative action time OEM No If required16
169 TnDt Integral action time OEM – If required
To ensure safe startup of the modulating pump, a start kick with the maximum pump
speed (QmodMin) is given for 10 seconds each time the pump is activated.
On completion of the start kick, the value calculated from the heat demand will be
adopted.
In normal heating operation, the pump runs at reduced speed (reduced volumetric flow)
for the greatest part of the operating time and the flow temperature will be appropriately
raised.
On the software side, both ∆T limitation and ∆T supervision can be switched on or off.
When the modulating pump is running, maximum limitation of the flow temperature
according to the adjusted value is always active.
In reduced operation, it is always the reduced (minimum) volumetric flow that is used, or
the ∆T supervison is active.
If the ∆T limitation and / or the ∆T supervision are active, they also acts in this operating
mode. It then works the same way as in normal operation, the only difference being the
lower flow temperature level.
The modulation function of the pump is deactivated since the heating is shut down.
In order not to extend the heating up phase due to the reduced volumetric flow, the plant
is always heated up with the full volumetric flow «NqmodNenn» within the first 30
minutes after reduced operation (night setback) or after plant shutdown (night
shutdown).
Then, a change to the volumetric flow is made that was calculated according to the
current outside temperature.
Summary of all ∆T
parameters (cont’d)
Behavior in different
operating modes
Pump overrun
Normal operation
(heating operation)
Reduced (setback)
operation
Shutdown mode
Heating up phase