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Benefit
Description
Setting
Effect
Frost protection
for the plant
Temperature-time
integral
244/348
Siemens Building Technologies
HVAC Products
4.230 D.h.w. priority
• Optimum allocation of boilers' heat output
Defines the priority of d.h.w. heating over space heating.
Setting range
0...3
During d.h.w. heating, space heating will be restricted, depending on the setting made.
Entry:
0
Absolute priority
The controller-internal heating circuit and the heating circuits of other controllers
connected to the LPB will be locked until the d.h.w. is heated up. The system
pump remains in operation provided it is located before the d.h.w. storage tank
and appropriately parameterized.
1
Shifting priority
If the capacity of the heat source is no longer sufficient, the amount of heat sup-
plied to the heating circuits will be restricted until d.h.w. heating is terminated.
2
No priority
D.h.w. heating and space heating at the same time.
In the case of tightly sized boilers and mixing heating circuits, the setpoint may
not be reached if the heating load is great, since too much heat is required for
space heating.
3
Shifting / absolute priority
If the capacity of the heat source is no longer sufficient, the pump heating circuits
will be switched off and the amount of heat supplied to the mixing heating circuits
restricted until d.h.w. heating is terminated.
Frost protection for the plant is fully active only in the case of setting 2. With setting 0 or
1, it will be partly or fully restricted. If the boiler is correctly sized, frost protection for the
plant is also ensured when using setting 1. In the case of plants where there is a con-
siderable risk of frost (e.g. plants with outdoor heating), setting 0 should not be used.
4.230.1
Shifting priority
The purpose of the function "Shifting priority" is to achieve optimum d.h.w. heating. This
means that during d.h.w. heating, the actual boiler temperature should be as close as
possible to the boiler temperature setpoint without shutting down the burner. To
achieve this, it may be necessary to restrict the heating circuits by means of a locking
signal. The signal is generated by a temperature-time integral.
This temperature-time integral generates the locking signal for restricting the heating
circuits.
Diagram
Procedure
a to b
Within a foreseeable period of time, the actual value of the boiler tem-
perature (TKx) will no longer be within the switching differential of the
boiler temperature setpoint.
Locking signal will be increased
b to c and
Within a foreseeable period of time, the actual boiler temperature (TKx)
will lie within the switching differential of the boiler temperature setpoint
d to e
Locking signal will remain at a constant level
Basic Documentation RVP540 / RVP550
Description of the heating engineer settings
Unit
–
Factory setting
1
CE1P2488en
18.10.2002
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