7
Generally applicable rules
for the proper use of this unit
The manufacturer’s warranty does not cover any indirect damage to the unit if the
mechanic installing the unit does not equip it with any additional electromagnetic devices
(thermostat, possibly in combination with a one-way valve) to protect the unit from damage
from malfunction under the following conditions:
Swimming pool system: If used with a high-performance collector and heat-sensitive
components (such as plastic lines), the supply line must have a excess temperature
thermostat with all of the necessary self-closing valves (closed when current less). The
controller’s pump output can provide this as well. Hence, all heat-sensitive parts would be
protected from overheating if the system were not running, even if steam were created in the
unit due to stagnation. This technique is mandatory, especially in systems with heat
exchangers, as a failure of the secondary pump might cause great damage to the plastic
tubes.
Conventional solar power systems with an external heat exchanger: in such systems, the
secondary heat transfer medium is usually pure water. If the pump runs at temperatures
below freezing because the controller fails, the heat exchanger and other components may
be damaged due to freezing. In this case, a thermostat must be installed on the supply line of
the secondary side after the heat exchanger to stop the primary pump automatically when the
temperature falls below 5°C, regardless of the output of the controller.
When used for floor and wall heaters: here, a safety thermostat must be used just as with
conventional heater controllers. It has to switch off the heating loop pump if there is
overheating regardless of the output from the controller to prevent indirect damage from
excess temperatures.
Solar power systems - tips on system standstill (stagnation):
Generally, stagnation is not a problem and cannot be ruled out if there is a power outage,
for instance. In the summer, the controller’s storage limit may switch off the system
repeatedly. Every system must thus be intrinsically safe. If the expansion container is
properly designed, this is ensured. Tests have shown that the heat transfer medium
(antifreeze) is under less stress during stagnation than when it is just below the steam phase.
All of the data sheets of the collector manufacturers list standstill temperatures above
200°C. However, these temperatures generally only occur during operation with dry steam,
i.e. when the heat exchange medium has completely turned to steam in the collector or the
collector has been completely emptied due to steam. The damp steam then dries quickly and
is no longer able to conduct heat. Hence, it can be assumed that these high temperature
cannot occur at the measuring point of the collector sensor (when installed in the collector
tube as usual) as the remaining thermal line would cool down the temperature via the metal
connections between the absorber and the sensor.
