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Siemens Building Technologies
Basic Documentation LMU54... / LMU64...
CC1P7494en
HVAC Products
3 Functions
07.11.2002
The PWM setting range of the temperature controller depends on the speed limitation
and the heat demand.
•
With inactive speed limitation:
The modulating range must be parameterized while giving consideration to voltage
variations.
LmodTL:
This limit must be set such that the heat output will not fall below the minimum
permissible output while taking into account voltage variations (undervoltage).
PhzMax, LmodVL:
This limit must be set such that the heat output will not exceed the maximum
permissible output while taking into account voltage variations (overvoltage).
Heating mode
DHW mode
Output limits with speed
limitation inactive
LmodTL, PhzMax
LmodTL, LmodVL
In addition, the following requirement must be met: PhzMax
≤
LmodVL
•
When speed limitation is active:
The modulating range of the temperature controller remains as wide as possible and
speed limitation limits the heat output to the required value.
- Upper limitation:
«NhzMaxAkt» in the case of heating demand, «N_VL» in the
case of DHW demand
- Lower limitation:
«N_TL» in the case of heating and DHW demand
To ensure a maximum modulating range will be reached and voltage variations in the
fan’s power supply can be offset, it is recommended to set the setting parameters of
output adjustment as follows:
LmodTL:
Minimum PWM value at which the flame is not yet lost (while giving consideration to
voltage variations).
PhzMax, LmodVL:
100 % (makes possible the maximum fan setting range).
If the associated speeds «NhzMax» and «N_VL» deviate too much from these PWM
values, there will be more and more overshoot when the fan speed attempts to adjust
itself on reaching the maximum heat output.
If such overshoot is not desired, the values can be reduced.
With the following operating modes, the heat output is statically predefined, that is, the
boiler controller’s results will be ignored and a value in accordance with the function is
delivered to the burner control.
Function
Required heat output
Chimney sweep function
PhzMaxAkt
Controller stop function
Set on the HMI or QAA73...
Controller delay
LmodRgVerz
Heat output limits
