Overview Solar 1 Boiler/Buffer



This function block realizes a solar control with one solar circuit and switching between boiler and buffer. Via a switchover valve, the solar yield is charged into either the boiler or the buffer.

If the solar temperature is higher than the temperature of the respective storage tank by the Hysteresis solar on and its temperature is below its maximum, the valve switches to this storage tank and the pump turns on:
  • Without Boiler priority the block first checks whether the boiler can be charged; only if it cannot does the buffer get its turn. When the collector cools down, charging therefore moves from the boiler to the buffer as long as there is still yield there.
  • With Boiler priority the valve stays on the boiler (VP = 0) until it has reached its Boiler maximum. Until then the buffer is not charged, even if more yield could be gained there.
The pump is switched off when the difference between solar and the storage tank currently being charged falls below the Hysteresis solar off or the solar, boiler or buffer temperature reaches its maximum value. Between the switch-on and switch-off threshold the last state is kept.

With the pump switched on, the speed is set proportional to the temperature difference: speed in per cent = Gain x (solar temperature - temperature of the storage tank being charged), limited to 0 to 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 Cylinder Buffer SO BO PU PD PA VP Input (sensor) Output

Inputs

BO Temp. boiler Temperature boiler. Not linked: the block calculates with 0 °C, the boiler is therefore regarded as cold and is charged preferentially. This sensor must be linked.
PU
 Temp. buffer
 Temperature buffer. Not linked: the block calculates with 0 °C. This sensor must be linked.
SO
 Temp. solar
 Temperature solar (collector). Not linked: the block calculates with 0 °C, the pump stays off.

Outputs
PU
 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.
VP Valve buffer Valve switchover boiler/buffer: 1 = buffer, 0 = boiler.

Parameters
Solar maximum
 Maximum temperature solar. If the temperature exceeds this value, the pump is switched off even if the storage tank temperature has not been reached.
Boiler maximum Switch-off temperature boiler. If the boiler temperature exceeds this value, boiler charging is ended.
Buffer maximum Switch-off temperature buffer. If the buffer temperature exceeds this value, buffer charging is ended.
Hysteresis solar on
 Difference between solar and storage tank at which the control becomes active.
Hysteresis solar off
 Difference between solar and storage tank at which the control becomes inactive.
Gain Control setting; the higher the value, the faster the analog output changes with a change in temperature.
Boiler priority If this parameter is active, the boiler is charged first. Only once the boiler maximum is reached is switching to buffer charging performed.

See also common parameters of all function blocks.