Technische Alternative ESR 31 Mode D'emploi page 6

English
Generally applicable rules
The manufacturer of the control unit cannot be held liable for any indirect damage to the
system if the party that installs the system does not install any additional electromechanical
devices (thermostat, possibly in combination with a one-way valve) to protect the system
from damage as a result of a malfunction under the following conditions:
 Solar thermal system for swimming pools: An excess temperature thermostat and a
self-actuating one-way valve (normally closed) must be installed in the supply line in
combination with a high-performance collector and heat-sensitive system components
(such as plastic lines). The valve can also be supplied from the control unit's pump
outlet. Thus, all of the heat-sensitive parts are protected from excess temperature if
the system is at standstill, even if steam (stagnation) occurs in the system. This ar-
rangement is prescribed in particular for systems with heat exchangers as a failure of
the secondary pump would otherwise cause great damage to the plastic tubes.
 Conventional solar thermal systems with external heat exchangers: in such systems,
the secondary heat transfer medium is usually pure water. If the pump runs at temper-
atures below freezing because the control unit has failed, there is a danger of the heat
exchanger and other parts of the system being damaged by frost. In this case, a ther-
mostat has to be installed directly after the heat exchanger on the supply line of the
secondary side to switch off the primary pump automatically if the temperature drops
below 5°C regardless of the control unit's output.
 In combination with floor and wall heaters: here, a safety thermostat is prescribed as
with conventional control units for heaters. It must switch off the heating circulation
pump to prevent indirect damage due to excess temperature regardless of the output
of the control unit.
Stagnation- Solar thermal systems - tips for system standstill:
In principle, stagnation is not a problem and cannot be ruled out, for instance due to a
blackout. In summer, the limited storage capacity of the control unit can cause the system to
shut down repeatedly. A system thus always has to be intrinsically safe. This safety is en-
sured if the expansion tank has the proper dimensions. Tests have shown that the heat trans-
fer medium (antifreeze) is under less stress during stagnation that shortly before the steam
phase.
The data sheets of all collector manufacturers have standstill temperatures above 200°C,
but these temperatures generally only occur in the operating phase with "dry steam", i.e.
when the heat transfer medium in the collector has completely evaporated or when the steam
has completely emptied the collector. The humid steam dehumidifies quickly and loses its
heat conductivity. Thus, it can be generally assumed that these high temperatures cannot
occur at the measuring point of the collector sensor (if installed in the collecting tube as usu-
al) as the remaining thermal line cools down the medium with its metal connections from the
absorber to the sensor.
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for the correct use of this control unit: