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Siemens Building Technologies
Basic Documentation RVD110, RVD130
CE1P2381E
HVAC Products
19 Function block Locking functions
27.05.2004
19.3.2 Maximum
limitation
with heating operation
The limit value used for maximum limitation in the heating circuit is generated from the
following variables:
•
Constant value (setting made on operating line 151)
•
Slope (setting made on operating line 152)
•
Start of shifting (setting made on operating line 153)
The current limit value can be determined as follows:
•
If the outside temperature is higher than or equal to the value set for the start of
shifting (setting made on operating line 153), the current limit value is the constant
value entered on operating line 151
•
If the outside temperature is lower than the value set for the start of shifting, the cur-
rent limit value T
L
will be calculated according to the following formula:
T
L
= T
L constant
+ [ ( T
L start
– T
A
) × s × 0.1 ]
T
PR
T
A
s
90
80
70
60
50
40
30
20
20
10
0
-10
30
T
L constant
T
L start
238
1D
0
3
S
Slope (operating line 152)
T
A
Actual outside temperature
T
L constant
Constant value (operating line 151)
T
L start
Start of shifting (operating line 153)
T
PR
Primary
return
temperature
Limitation operates as a function of the selected characteristic:
•
When the outside temperature falls, the return temperature will first be limited to the
constant value
•
If the outside temperature continues to fall, it will reach the set starting point for shift-
ing. From that point, the limit value will be raised as the outside temperature falls.
The slope of that part of the characteristic is adjustable.
The setting range reaches from 0 to 40. The effective value is 10 times smaller.
This function can be deactivated on operating line 151.
19.3.3 Maximum limitation with d.h.w. heating
In contrast to maximum limitation in the space heating mode, a constant value is used
for maximum limitation in the d.h.w. heating mode. It is to be set on operating line 154.
The function also acts on two-port valve Y1 in the primary circuit.
To be able to reach the required storage tank temperature, a specific maximum set-
point for the return temperature acts during the period of time the legionella function is
active. If set to inactive, (operating line 157 =
- - -
), there will be no return temperature
limitation during the period of time the legionella function is active.
With plant types no. 4, 5 and 6, there is no maximum limitation in the case of d.h.w.
heating, since there is no sensor.
If both the heating and the d.h.w. circuit call for heat
and
maximum limitation of the
return temperature acts on both circuits, the higher of the two limit values will be used.
