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
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, 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.

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 block has no speed output: the settings for speed, controller and start-up time do not apply, yield and operating hours calculate with full delivery. The additional functions apply per pump (collector field); an unconnected collector 2 is ignored. Boiler and buffer count as storage, in forced operation the block sets the valve itself.

See also common parameters of all function blocks.