KT-Elektronik SOL3-3, Installation And Owner'S Manual, Page: 42 / 88

Installation and operating manual KT-Elektronik
5.6 Rotation speed control
It might make sense to run the pump with a lower flow rate at low solar radiation. By
doing so, the following can be achieved:
–
a higher temperature is reached at the collector. This impairs the efficiency of the
collector, but allows to heat up a small amount of water in the storage.
–
the power consumption of the pump is reduced.
Basically, the turn on and off conditions for the pumps apply as without rotation speed
control. Additionally, the 0...10V-output is provided with rotation speed information when
the pump is running.
The following speed control modes are available:
1 - Constant temperature difference
The rotation speed is regulated such that the temperature at the collector is higher by a
certain value (factory default setting 8K) than at the storage. The programmed value is
usually exceeded at high solar radiation, what causes the pump to run at 100%. Once
the difference drops below the set-point, the flow rate is reduced. The temperature in the
collector flow thereby increases again and the difference remains at the set-point.
If a return flow sensor is present, the temperature difference between the collector
sensor and the return flow sensor is corrected, if flow and return flow sensor exist, then
the difference between these two is corrected.
2 - Constant collector temperature
Only the collector temperature (or collector flow sensor, if present) is considered. It is
adjusted to the programmed set-point (e.g. 60°C). The programmed value is usually
exceeded at high solar radiation, the controller runs the pump at 100%. If the solar
radiation becomes weaker, so that the temperature drops below the set-point, the
controller reduces the rotation speed of the pump, thereby the heat carrier medium
remains for a longer period in the collector and the temperature increases again. In case
the solar radiation decreases such that the temperature can't even be hold at the
minimum rotation speed set (e.g. 30%), then the controller signalizes 0% which equals
0V which turns the pump off if this has not been done yet by means of a normal turn-off
condition.
A rotation speed control is only available for one single pump. This might therefore not
be reasonable for system variants with more than one pump. In system variants with
external heat exchanger, the storage circuit rotation speed is always regulated whereas
the pump (-s) in the collector circuit are run with a constant rotation speed. A uniform
temperature distribution in the collector is achieved this way, which improves the
collector efficiency.
The SOL3 controller has a 0...10V-output that can be connected to the input of a
corresponding pump. Parameter settings can curtail the voltage range of this variable:
If the calculated value is above the programmed maximum rotation speed value, a signal
for 100% is sent (corresponding to 10 V output). If the calculated value is below the
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EB_37383_SOL3-3_EN002