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Siemens Building Technologies Basic Documentation LMV5... CC1P7550en
HVAC Products 8 Commissioning instructions for the LMV5... system 13.08.2004
Example: Modulating control
After the boiler setpoint in °C has been entered, the switch-on and switch-off point of
the 2-position controller in % will be given.
The switching points will be calculated in relation to the current setpoint.
Example: Setpoint: 70 °C
SD_ModOn +5 % ( = 3.5 K)
SD_ModOff +10 % ( = 7 K)
Controller loop open (Off) 70 + 3.5 = 73.5 °C
Controller loop closed (On) 70 - 7 = 63 °C
Menu level 1 Menu level 2 Menu level 3 Menu level 4 Menu level 5 Menu level 6
Params & Display
LoadController
ControllerParam
SD_ModOn
SD_ModOff
Setpoint Actual value
7550f07E/0502
R=ON
Y=OPEN
Y=CLOSED
W
SD_ModOff
SD_ModOn
When the cold start thermal protection has been activated, a boiler – after having dropped
below a predefined switch-on threshold – will be heated up in multistage operation.
This approach ensures that when cold, the boiler does not have to satisfy the maximum
demand for heat within a very short period of time. Thermal strain on the boiler will thus
be prevented.
The cold start sequence will be activated when, on startup, the actual value lies below
the switch-on threshold. When cold start thermal shock protection is activated, the ma-
nipulated variable - on cold start - will be increased in a stepwise fashion using the ad-
justed output step (or the next stage will be switched on).
Start output for the cold start is the minimum load. The increase of the output by the
output step depends on 2 criteria:
1. If the predefined change of the actual value is not reached with the current output
(setpoint step modulating or setpoint step multistage), the output will be increased
by this step (output step) when the maximum time has elapsed.
2. If the predefined change of the actual value is reached with the current output within
the maximum time, the output will be increased by one output step.
When the switch-off threshold is reached, the cold start sequence will be terminated
and normal control operation started.
2-position controller
(C = ON / OFF)
Diagram
Cold start thermal shock
protection (CSTP)
Description
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