54
Instructions on commissioning, maintenance, and troubleshooting for auroSTOR 0020111119_02
7.4
Setting the flow rate in the solar circuit
In addition to factors such as the temperature, pipe
diameter, number of collectors and so on, the flow rate
is important for ensuring optimum heat transfer. A flow
rate above the nominal flow rate is not as unfavourable
as a flow rate below the nominal flow rate.
i
Never allow the flow rate to fall below the nomi-
nal flow rate. Doing so can cause the efficiency
of the collectors to drop significantly, resulting
in a solar yield of up to 10% less and unneces-
sarily high power consumption by the solar
pump.
The solar pump unit has a three-stage solar pump and a
flow rate limiter to enable it to optimally modify the flow
rate in line with the collector performance.
– In conjunction with central air vents, the flow rate in the
solar circuit should be at least 3 l/min so that the resi-
dual air in the system is pulled along with the solar fluid
and conveyed to the air vents.
– You must maintain a flow rate of at least
0.25 l/m
2
min in the collector array.
– In the case of small systems with a net area of up to
10 m
2
, a flow rate of 0.50 to
0.67 l/m
2
min is recommended in the collector array.
– In the case of larger systems, the flow rate in the collec-
tor array must be lower than 0.50 l/m
2
min.
For a suitable nominal flow rate for the collectors, pipe
diameter, and pipe length used, see Tab. 6.1 and 6.2.
0,
5
1
2
3
0,
5
1
2
3
4
5
6
4
5
6
L/
min
L/
min
1,1l/min
2
1
Fig. 7.2 Flow rate limiter
>
Determine the nominal flow rate to be set from Tab.
6.1/6.2.
>
Completely open the flow rate limiter with the control
valve (
1
).
>
Allow the solar pump to run on the lowest pump speed.
>
Check the flow rate on the indicator (
2
) of the flow rate
limiter.
>
Choose a pump speed that sets the flow rate to equal to
or more than the nominal flow rate.
– If the actual flow rate is lower than the nominal flow
rate, switch to the next higher pump speed.
– If the nominal flow rate cannot be reached even at the
highest pump speed, check to see whether it is possi-
ble to connect less collectors in series and to switch to
a combination of series and parallel connections.
Check out other ways of reducing the pressure loss.
Observe here the Vaillant solar planning information.
>
Use the control valve (
1
) of the flow rate limiter to set
the flow rate so that it is slightly higher than the nominal
flow rate.
If you are using the auroMATIC 620 controller, you can
use the set flow rate to calculate the yield.
>
Enter the set flow rate on the controller; the controller
then calculates the yield.
For more information, see the operating and installation
instructions for the controller.
i
Set the flow rate in the solar circuit as specified
in
¬ tab. 6.1
or
¬ tab. 6.2
.
7 Commissioning
