Overview Solar 2 Boiler/Buffer



This function block realizes a solar control with two solar circuits (e.g. two collector fields) and switching between boiler and buffer. Each solar circuit has its own pump (digital); a shared switchover valve determines whether the currently charged storage tank is the boiler or the buffer.

Switchover valve (VB): As long as one of the two collectors is warmer than the boiler by the Hysteresis boiler-solar on and the boiler has not yet reached its maximum, the valve switches to boiler (VB = 1). Otherwise (both collectors below the Hysteresis boiler-solar off or boiler full) it switches to buffer (VB = 0).

Pump solar 1 and pump solar 2 switch on independently of each other when the respective collector temperature is warmer than the active storage tank by the hysteresis belonging to the active storage tank (boiler-solar or buffer-solar) and its maximum is not reached. They switch off when the difference falls below the threshold or the storage or solar maximum temperature is reached. Between the switch-on and switch-off threshold the last state is kept, so the switch-on hysteresis must be greater than the switch-off hysteresis.

Both collector circuits always charge into the same storage tank - the valve applies to both. This block controls the pumps digitally only, there is no speed output. The control runs once per second.


System diagram

Collector 1 Collector 2 Cylinder Buffer S1 S2 BU PU P1 P2 VB Input (sensor) Output

Inputs

BU Temp. boiler Temperature boiler (bottom). Not linked: the block calculates with 0 °C, the boiler is therefore regarded as cold and the valve stays on boiler permanently. This sensor must be linked.
PU
 Temp. buffer
 Temperature buffer (bottom). Not linked: the block calculates with 0 °C. This sensor must be linked.
S1
 Temp. solar 1
 Temperature solar 1 (collector 1). Not linked: the block calculates with 0 °C, pump solar 1 stays off.
S2
 Temp. solar 2
 Temperature solar 2 (collector 2). Not linked: the block calculates with 0 °C, pump solar 2 stays off. If only one collector array is used, leave this input free.

Outputs
VB
 Valve boiler
 Valve switchover boiler/buffer: 1 = boiler, 0 = buffer.
P1
 Pump solar 1
 Pump solar circuit 1 on/off.
P2
 Pump solar 2
 Pump solar circuit 2 on/off.

Parameters
Solar max.
 Maximum temperature solar. If a collector exceeds this value, the respective solar pump is switched off.
Buffer max.
 Switch-off temperature buffer. If the buffer temperature exceeds this value, buffer charging is ended.
Boiler max.
 Switch-off temperature boiler. If the boiler temperature exceeds this value, boiler charging is ended.
Hysteresis buffer-solar on
 Difference between solar and buffer at which buffer charging becomes active.
Hysteresis buffer-solar off
 Difference between solar and buffer at which buffer charging becomes inactive.
Hysteresis boiler-solar on
 Difference between solar and boiler at which switching to boiler charging is performed.
Hysteresis boiler-solar off
 Difference between solar and boiler at which boiler charging becomes inactive.

See also common parameters of all function blocks.