Siemens LMS14 User Manual page 238

Basics of dynamic supervision
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Building Technologies Division
When a heating circuit pump is activated, the pressure downstream from the pump
rises and the pressure upstream drops. These pressure changes depend on the pump
head and the volumetric flow.
Function:
The pressure sensor acquires the water pressure before and after the pump is
activated. To ensure the pump functions correctly, the pressure differential must exceed
a certain minimum threshold Dyn superv press diff min (2491).
At the same time, the pressure differential must not exceed the maximum threshold
Dyn superv press diff max (2492), possibly an indication of too little water circulation or
no circulation at all.
If these criteria are not satisfied, startup is prevented for the period of time Dyn Press
pause [4200.1] and a status code is delivered. If this start prevention occurs
successively the number of times parameterized under DynPress repetitions
the unit initiates lockout if activated via parameter Dyn press superv sh'down (2490).
If, during start prevention, the pump continues to run, it will be locked in the last
seconds (Tdelay + 2 s) of start prevention in order to be able to acquire the pressure
change as the pump is reactivated upon a new boiler release.
Note!
With manual control, the pump cannot be deactivated, due to fixed control of the
actuators.
This means that the dynamic pressure test cannot be repeated.
For this reason, manual control is ended in this case, enabling the tests to be
repeated.
The pressure thresholds can be parameterized in the range from 0...5 bar with a
resolution of 0.02 bar. Pressure threshold checking is deactivated by selecting 0 bar as
the minimum value and 5 bar as the maximum value.
Parameter Dyn superv press increase (2494) is used to define whether a pressure
increase or decrease is expected when the pump is activated.
Note!
If a plant diagram without boiler pump (Q1) was configured, this function must be
deactivated.
The differential pressure is checked on completion of Tdelay after the pump has been
activated.
Then, as the pump runs, the differential pressure is not checked anymore.
If a configuration with water pressure sensor was selected and supervision of water
circulation is released Dyn superv press diff min (2491)/Dyn superv press diff max
(2492), the LMS14... must read in a valid value for the water pressure. Otherwise,
either startup is prevented and a status code is delivered, or the unit goes to lockout
Dyn press superv sh'down (2490).
Tdelay is calculated as follows:
Tdelay = 5 * Dyn press superv tme const (2496) + DynPress pump delay [4198.1]
This means that the pressure signal after Pump on is acquired with a certain delay
when Tdelay has elapsed.
The pressure signal is acquired for a period of time called Dyn press superv time
(2495).
User Manual LMS14...
6 The settings in detail
[4199.1]
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CC1U7471en
07.05.2014