Overview Solar system protection



This function block keeps a solar system alive in summer and in winter. It sits between the solar block (for example Solar buffer basic) and the pump and switches the pump against the normal control when necessary: system protection, frost protection and collector and storage cooling. Without these functions the system boils in August and freezes in January - both cost the solar fluid.

As before, the solar block supplies the pump request (at input PE) and, for a speed-controlled pump, the speed (input DE). The protection block passes both through as long as there is no protection case. The pump is driven by outputs PU and DR of this block, no longer by the solar block.

The same protection functions can also be set directly in the solar blocks (see Solar blocks: additional functions). This block remains for systems that do not want to change their solar blocks.

Priority

If several cases apply, the topmost one counts. The priority is the actual content of the block - whoever swaps it makes the system boil.

Rank Case Pump
1 System protection. The collector is too hot, the solar fluid would evaporate. Highest priority, also before frost protection. OFF
2 Sensor fault. The collector sensor is missing or outside the plausible range. OFF
3 Frost protection. The collector is about to freeze. ON
4 Collector cooling. The collector is very hot, but the storage is still below its upper limit. ON
5 Storage cooling. Excess heat is removed at night. ON
6 Normal control. PE and DE are passed through. per PE

System protection. Above the threshold the pump is switched off and released again only when the collector is below it by the reset difference. Threshold 0 switches the system protection off.

Frost protection. If the collector falls below the threshold, the pump runs and takes heat from the storage. It may give up: if the storage falls below the minimum storage temperature, the frost protection switches off - frost protection that drains the storage does more damage than the frost. It starts again only after the collector has risen above the threshold plus reset difference and fallen again afterwards. It needs a connected storage sensor.

Collector cooling. If the storage is full, the solar block stops the pump and the collector keeps heating up. The collector cooling lets the pump run anyway from the set collector temperature so that the system protection does not trip. It never runs beyond the storage upper limit: without this absolute limit the storage boils, and in a hot water storage that becomes life-threatening. The function is off by default and needs a connected storage sensor.

Storage cooling. In the set time window - it may span midnight, equal hours mean the whole day - excess storage heat is removed through the collector. Cooling starts at the storage temperature storage cooling from storage and ends at the target temperature, and only as long as the collector is colder than the storage by the minimum difference. As long as the clock of the controller is not set, nothing is cooled. The function is off by default and needs a connected storage sensor.

Enable and lock affect only the normal control and the storage cooling. Frost protection, collector cooling and system protection remain - they protect the system.

Speed. The passed-through request is raised to the minimum speed, because below about 30 % no pump delivers reliably. The protection functions run at the speed for protection functions. Without a connected DE the pump runs at 100 % on request.

Example

Solar system with 16 m² collector and a 1000 litre buffer. The block Solar buffer basic gets the collector and buffer sensors and reports the pump at output PD. This output goes to PE of the protection block, the sensors also go to KT and ST, and PU switches the pump. Collector cooling on from 120 °C with an upper limit of 90 °C, system protection at 140 °C. Result: if the buffer is full, the pump keeps cooling the collector until the buffer reaches 90 °C; if the collector gets too hot anyway, the pump stands still until it is back to 130 °C.

Inputs

KT Collector temperature Mandatory input. Not connected or outside the plausible range: fault, pump off.
ST Storage temperature Optional. Limit for frost protection, collector cooling and storage cooling. Not connected or outside the plausible range: these three functions are off, system protection and normal control keep working.
PE Pump request solar block Not 0 requests the pump. Passed through in the normal control. Not connected: the pump never runs in the normal control.
DE Speed request solar block in % Optional. Passed through when the pump is requested, at least at the minimum speed. Not connected: 100 %.
FR Enable Optional. 0 blocks the normal control and the storage cooling, not 0 enables. Not connected: enabled.
SP Lock Optional. Not 0 blocks the normal control and the storage cooling, 0 enables. Not connected: never locked.

Outputs
PU Pump On/off. The result of priority and normal control.
DR Speed in % Speed for a pump with analogue control. 0 while the pump is off.
KK Collector cooling active 1 during collector cooling.
SK Storage cooling active 1 during storage cooling.
AS System protection active 1 as long as the pump is forced off because the collector is too hot.
FS Frost protection active 1 during frost protection.
SM Status text State in plain text (German, ASCII, written by the runtime), for example "Normalbetrieb", "Kollektorkuehlung 128 C", "Frostschutz 1.0 C". For a text address.
SR Fault 1 with a missing or implausible collector sensor.

Parameters
System protection from collector, reset difference Default 140 ° and 10 K. Threshold 0 = off.
Frost protection, from collector, reset difference, minimum storage temperature Default on, 2 °, 2 K and 15 °.
Collector cooling, from collector, reset difference, storage upper limit Default off, 120 °, 5 K and 95 °.
Storage cooling, from/to, from storage, target temperature, minimum difference Default off, 22 to 6 o'clock, 70 °, 60 ° and 5 K.
Collector sensor minimum/maximum Plausible range. Default -40 ° to 200 °.
Minimum speed, speed for protection functions Default 30 % and 100 %.

See also general parameters of all function blocks.