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Siemens Building Technologies
Basic Documentation RVP540 / RVP550
CE1P2488en
HVAC Products
General control processes
04.11.2009
•
Maximum flow temperature
T
VMax
Variant 1:
Setting the maximum flow temperature defines the maximum flow tem-
perature setpoint.
Variant 2:
Setting the maximum flow temperature defines the maximum flow tem-
perature setpoint on the one hand. On the other, the same setting defines the
range from what flow temperature the pump speed shall be increased.
T
VMax
should always be selected as high as this is permitted by the heating system.
The higher
T
VMax
, the longer the pump runs at
n
Red
. Also, the heating circuit’s maxi-
mum output will not be restricted unnecessarily.
•
Power factor
LF
Of importance only in connection with variant 2.
Figure 1 shows that at outside temperatures below point C, the pump speed will be
increased from the reduced speed to the maximum speed. To define the rate at
which the pump speed shall be increased, the radiators’ power factor is to be set.
The power factor defines the ratio of radiator output at the reduced pump speed
n
red
and radiator output at the maximum pump speed.
speed
pump
imum
max
at
output
Radiator
speed
pump
reduced
at
output
Radiator
LF
=
This factor is fixed at 85 %. If the plant is correctly designed and sized, this setting
always ensures a satisfactory performance.
•
Heating curve slope ”s”
Variant 1:
the heating curve slope must be set for the maximum pump speed.
Variant 2:
the heating curve slope must be set for the reduced pump speed.
The correlation between the heating curve slope for the maximum speed
s
nMax
and
the heating curve slope for the reduced speed
s
nRed
is defined by
LF
s
s
nMax
nRed
=
In the case of fixed value LF = 85 %, this means:
nMax
nRed
s
s
⋅
=
18
.
1
6.7.5 Control
of
pumps
with no speed control
If pumps with no speed control shall be controlled, the reduced pump speed
must
be
set to the level of the maximum speed.