Load Limitation - Siemens LMU54 Series Basic Documentation

Load limitation

Siemens Building Technologies
HVAC Products
When defining the minimum and maximum heat output, the «Speed limitation» function
is of importance. This function is selected via parameterization:
KonfigRg5.2 = 0: Without speed limitation
KonfigRg5.2 = 1: With speed limitation
• Without speed limitation
In that case, the limit values selected for the setting range of heat output are the PWM
control values of the fan.
Supply voltage variations have an impact on the heat output and the fan will not catch
up. The maximum heat output or the modulating range can be determined with the help
of the following graph, depending on the type of plant components connected:
Heat output
(control of fan)
100 %
LmodVL
Max. heat output without RU
Max. heat output with RU
LmodTL
7494d01E
Modulating range of the LMU... without speed limitation
The output limits in the case of heat demand are dependent on the connection of a RU.
The following table shows the assignment:
RU Maximum heat output PhzMaxAkt
Present See calculations below
Not present PhzMax
Formula to be used for weather compensation without room influence via the RU:
RelModLevSet

PhzMaxAkt =
100 %
RelModLevSet: The relative modulation level setting specifies the maximum degree
of modulation of the RU in % of the modulating range.
Basic Documentation LMU54... / LMU64...
3 Functions
Modulating range with RU
Modulating range without RU
Modulating range d.h.w.
Max. modulating range
• (PhzMax – LmodTL) + LmodTL
Output signal of
temperature controller
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CC1P7494en
07.11.2002