Siemens LMU54 Series Basic Documentation page 47

Siemens Building Technologies
HVAC Products
• With speed limitation
When speed limitation is active, disturbing effects on the fan's speed (voltage variations,
changes in resistance on the flue gas side) will be offset with regard to output limits.
For that purpose, the associated speeds must be matched to the heat output measured
at the boiler. Like without speed limitation, the modulating range or the maximum heat
output can be specified in the form of fan speed.
Heat output
(fan speed)
N_VL
Max. speed without RU
Max. speed with RU
N_TL
7494d02E
Modulating range of the LMU... with speed limitation
The output limits in the case of heat demand are dependent on the connection of an RU.
The following table shows the assignment:
RU Maximum heat output
Present See calculations below
Not present NhzMax
Formula to be used for weather compensation without room influence via the RU:
RelModLevSet

NhzMaxAkt =
100 %
RelModLevSet: The relative modulation level setting specifies the maximum degree
of modulation of the RU in % of the modulating range.
If there is demand for DHW, the maximum output is always predetermined by «N_VL».
With regard to heat demand, the following thus applies to the output or speed range:
Demand for space
heating
Minimum output N_TL
Maximum output NhzMaxAkt
Basic Documentation LMU54... / LMU64...
3 Functions
Modulating range with RU
Modulating range without RU
Modulating range DHW
«
NhzMaxAkt
(NhzMax – N_TL) + N_TL
•
Demand for DHW heating
N_TL
N_VL
Output signal of
temperature controller
»
CC1P7494en
07.11.2002
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