Solar priority
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Solar priority
In solar heating systems used to charge more than one consumer (such as a cylinder, a buffer, and a
basin), priorities must be set for the various circuits. There are basically two sets of rules used for a
system of priority and lower priority assignment.
Absolute priority
: Only when a cylinder that has priority has reached its upper limit for tem-
perature does the system switch to the next lower priority.
Relative priority
: The charge begins with the colder cylinder (because the collector will reach
the differential here first), even if this cylinder does not have priority.
While the consumer that does not have priority is being charged, the device monitors the collector
temperature. If the collector temperature once again reaches the switch-on differential for the con-
sumer currently being charged while the pump is running, the priority timer is activated. If a radiation
sensor is used, it must exceed at threshold value in lieu of the switch-on differential.
The priority timer switches the pump off for delay time 1 (60 sec). After flushing (1, 3), the computer
then calculates the increasing collector temperature. It recognizes whether the set delay time 2 td will
suffice to heat up the collector to the priority temperature (5). If not, the system waits for priority tem-
perature to be reached before switching (case 2). If the computer determines that the increase will not
suffice within the delay time 2 td (case 4), it interrupts the procedure and disables the priority timer
until runtime tr has expired.
If runtime = 0, the lower priority is allowed once the maximum threshold of the current priority
has been reached. In other words, the system is switched to absolute priority assignment
mode.
