Overview Solar buffer simple



This function block realizes a simple solar control for charging a single buffer. Either a pump via switching hysteresis (digital) or a pump with analog or PWM control can be used.

The pump is switched on when the solar temperature is higher than the buffer temperature by the Hysteresis on and both the buffer and solar temperatures are below their maximum values. It is switched off again when the difference falls below the Hysteresis off or the buffer or solar temperature reaches its maximum value. Between the two thresholds the last state is kept, so Hysteresis on must be greater than Hysteresis off.

With the pump switched on, the speed is set proportional to the temperature difference: speed in per cent = Gain x (solar temperature - buffer temperature), limited to 0 to 100 %. With a Gain of 5 and a difference of 20 K the pump therefore runs at 100 %. The value is present at the output Pump analog 0-100%; with the pump switched off it is 0. The control runs once per second.


System diagram

Collector Buffer SO PU PD PA Solar pump Input (sensor) Output

Inputs

PU Temp. buffer bottom Temperature buffer bottom. Not linked: the block calculates with 0 °C, the switch-on condition is then almost always met and the pump runs permanently. This sensor must be linked.
SO
 Temp. solar
 Temperature solar (collector). Not linked: the block calculates with 0 °C, the pump stays off.

Outputs
PD
 Pump digital
 Pump digital on/off.
PA
 Pump analog 0-100%
 Pump analog. As an alternative to control via switching hysteresis, a pump with analog control can be used at this output.

Parameters
System protection from collector
 System protection, always active (formerly Solar max.; an existing value is kept). Above this collector temperature the pump is switched off because the solar fluid would evaporate, even if the storage is not yet reached. It starts again only when the collector is below it by the reset difference (see additional functions).
Buffer max.
 Switch-off temperature buffer. If the buffer temperature exceeds this value, the solar pump is switched off.
Hysteresis on
 Difference between solar and buffer at which the control becomes active.
Hysteresis off
 Difference between solar and buffer at which the control becomes inactive.
Gain Control setting; the higher the value, the faster the analog output changes with a change in temperature.

Additional functions

This block additionally has run-on, start-up time, PID speed, tube start, system protection, frost protection, collector and storage cooling, sensor monitoring, yield estimate and operating hours. System protection (with the former switch-off temperature Solar max.) and sensor monitoring are always active, all other functions are off by default, so the system behaves as before; each of these is switched on with a check mark in the parameters. Inputs (FR, SP, QI), outputs (SM, SR, KK, SK, AS, FS, WA, BH, LE, ET, EG), parameters and the priority are described under Solar blocks: additional functions.

The buffer (input PU) counts as storage.

See also common parameters of all function blocks.