49
4.2.5
Plate heat exchanger, buffer tank with preheat storage tank
If, in the 'System
selection’'
menu, the points "Plate
heat exchanger", "Buffer
tank with ...",
"Pre-heating storage" and
"Basic" are selected, the
hydraulic diagram
illustrated here is
available for use as a
basic system.
•
"Basic" diagram: The regulator constantly records the differential temperature between the sensors
T1 and T2. If the set switch-on differential temperature (parameter: 'diff. temp. solar ON') is
reached, the solar circuit pump R3 switches on and heats the solar circuit with the plate heat
exchanger. If the temperature level on the plate heat exchanger T3 reaches a value of at least 5
Kelvin more than the 'lower part of the storage tank' temperature T2, R1 switches on with minimum
speed and then regulates the temperature of the charging current at the required value (parameter:
‘charging setpoint'). This happens as long as either the maximum storing temperature (parameter:
''storage max.') is reached or the differential temperature between T3 and T2 falls below a value of
3 Kelvin. The solar circuit pump R3 remains active until either the maximum storing temperature
(parameter: ''storage max.') is reached or falls below the switch-off differential temperature of the
solar circuit (parameter: 'diff. temp. solar OFF'). To protect the charging circuit from overheating,
the solar circuit is deactivated when T3 is only 3 Kelvin below the maximum charging temperature
(parameter: 'Max. charging temp.'). If the charging circuit continues to heat up because of an
erroneous function, R1 is also deactivated when the maximum charging temperature is reached.
If the pre-heating storage temperature at T6 falls below the required temperature (parameter:
'Requir. pre-heat. st.') by 2 Kelvin and if the temperature in the buffer tank (T4) is at least 6Kelvin
higher than the required temperature (parameter: ‘Requir. pre-heat. st.'), the circuit pumps R2 and
R4 are switched on. The speed control of R2 ensures the charging temperature for the preheat
storage tank (T5) is kept constant at the required temperature (Parameter: 'Requir. pre-heat. st.').
R4 runs with constant volume flowing. The preheating storage is charged until the temperature at
T7 reaches the required temperature (parameter: 'Requir. pre-heat. st.') or the temperature at T4
has fallen below the value for the required pre-heating temperature plus 2 Kelvin. If one of these
two conditions is met, the pumps R2 and R4 are switched off.
To prevent erroneous settings, the described switch-on and switch-off values are interlocked,
this means they can be set only at a specific value to one other.
Since with this diagram, speed controls are only useful when the objective is "absolute
temperature", this control objective has been saved both in the settings "Absolute temp." and
also "Differential temp.". The control devices are therefore dependent on this setting.
