Solar Loop Controller
The solar loop controller is a two-channel controller that regulates the pump in the solar-loop.
The controller regulates the status and flow rate of up to two pumps based on the temperature difference of two distinct measured values.
The controller has 2 (plus 3 optional) analogic inputs.
The controller has 1 (plus 3 optional) outputs (partially digital and partially analogic).
Block Diagram
The block diagram shows the employed measuring and controlling values.
Controller Input Mask “Fixed Flow Rate“
With this setting the solar pump cuts in as soon as the collector outflow temperature is 6 degrees higher than the temperature in the tank on layer 5. The flow rate is 60 l/h for the collector field as a whole.
Controller Input Mask “Specific Flow Rate”
With this setting the solar pump cuts in as soon as the collector outflow temperature is 6 degrees higher than the temperature in the tank on layer 5. The flow rate is 15 l/h/m2 of collector field.
Controller Input Mask “Matched Flow”
With this setting the solar pump cuts in as soon as the collector outflow temperature is 6 degrees higher than the temperature in the tank on layer 5. The flow rate ranges between 50 and 100 l/h for the collector field as a whole as an attempt is made to reach an output temperature of 60°C.
Input Values
Collector Temperature [°C]
The value refers to the point where the temperature of the collector is measured. Enter either the collector mean or outflow temperature.
Tank Temperature [°C]
The value refers to the point where the tank temperature is measured. Enter the relevant tank layer.
Aperture Area of Collector [m2] (Required in Case of Specific Flow Rate)
The value refers to the aperture area of the selected collector. This value enables a pump to be controlled with a specific flow rate.
Inlet Temperature of Collector [°C] (Required in Case of Matched Flow Operation)
The collector’s inlet temperature is used to define the pump flow rate in “Matched flow” mode. To this end measure pipe temperature at collector’s inlet.
Yield of Collector Field [W] (Required in Case of Matched Flow Operation)
The yield of the collector field is used to define the pump rate in ”Matched flow“ mode. Select the relevant collector field.
Description of Control Parameters
Description
The “description“ value enables the user to assign controllers any name or number. Polysun assigns a consecutive number as a standard feature as different controllers are added chronologically in the hydraulic system.
Sign of Output
The term “Normal“ means that digital output signals are controlled as intended in the switching logics. (Example: if X1>X2 the output of pump 1 is positive)
The term “Inverted” that output signals are multiplied -1.
(Example: if X1>X2 the output of pump 1 is equal to zero)
Maximum Temperature of Collector [°C]
If collector temperature X1 is higher than the entered maximum temperature the solar-loop pump cuts off.
Maximum Temperature of Tank [°C]
If tank temperature X2 is higher than the entered maximum temperature the solar-loop pump cuts off.
Cut-in Temperature Difference [K]
If the collector outflow temperature X1 is higher than tank temperature X2 by the entered value, the solar-loop pump cuts in.
(Example: if X1 > X2 + value, the pump cuts in)
Cut-off Temperature Difference [K]
If the collector outflow temperature X1 is lower than tank temperature X2 plus the entered value, the solar-loop pump cuts off.
(Example: if X1 < X2 + value, the pump cuts off)
Definition of Flow Rate Setting
- Specific flow rate
The controller regulates the pump according to the aperture area of the collector field by means of the value entered in the “Specific Flow rate”. The corresponding pumps should be set to “Flow rate setting“ (Double-click on pump to adjust the required settings). - Fixed flow rate
Selecting a fixed flow rate the pump is controlled by means of the value entered in the ”Fixed flow rate“ field. The input value “Aperture area of collector“ has no relevance and will be hidden. The corresponding pumps should be set to “Flow rate setting“ (Double-click on pump to adjust the required settings). - Matched Flow
In case of “matched flow“ operation the flow rate of the pump will be defined by means of a preset flow rate range. In the process the flow rate will be set so as to allow the collector output temperature to be reached. The corresponding pumps should be set to “Flow rate setting“ (Double-click on pump to adjust the required settings).
Definition of Flow Rate Value
- Specific flow rate [l/h/m2]
Value of the specific flow rate in [l/h/m2] aperture area of collector field. - Fixed flow rate [l/h]
Value of the required fixed flow rate of collector field. - Matched flow:
Value used to define the variable flow rate: collector outflow temperature [°C]; minimum flow rate [l/h], maximum flow rate [l/h].
Output Values
Status Pump 1
This digital output refers to the solar-loop pump to be controlled. Select the relevant pump from the list.
Status Pump 2 (Optional)
This digital output is activated just like the output of Status Pump 1. A second component (e.g. a further pump) may be controlled based on the same criteria as Status Pump 1. Select the relevant component from the list.
Flow Rate Pump 1 (Optional)
This analogic output controls the flow rate of pump 1. Select the relevant pump from the list. (the output is active only if the option “Flow rate setting” has been selected in the field “Flow rate-controlled” for the pump to be controlled; otherwise pump settings will have priority over the analogic control outputs. Double click on the pump to change/check the settings)
Flow Rate Pump 2 (Optional)
This analogic output performs the same function as the flow rate output of pump 1. Select the relevant pump from the list.
Overview of Control-Dependencies
Table: Control-dependencies of the flow rate pump
| Outputs | Parameter | Tip | Inputs | Function |
| Y1: Status Pump 1 Y1 = Y2 Y2: Status Pump 2 | Fixed flow rate | Set pump to – Flow rate setting – | X1: Collector temperature | Y1=0 if X1 > maximum collector temperature [°C] |
| X2: Tank temperature | Y1=0 if X2 > maximum tank temperature [°C] | |||
| X1: Collector temperature | Y1=1 if X1 > X2 + cut-in temperature difference [K] Y1=0 if X1 < X2 + cut-off temperature difference [K] | |||
| X2: Tank temperature | ||||
| Y3: Flow rate Pump 1 Y3 = Y4 Y4: Flow rate Pump 2 | Specific flow rate | Set pump to – Flow rate setting – Flow rate dependent on X3 and the value of the specific flow rate | X1: Collector temperature | Y1=0 if X1 > maximum collector temperature [°C] |
| X2: Tank temperature | Y1=0 if X2 > maximum tank temperature [°C] | |||
| X1: Collector temperature | Y1=1 if X1 > X2 + cut-in temperature difference [K] Y1=0 if X1 < X2 + cut-off temperature difference [K] | |||
| X2: Tank temperature | ||||
| X3: Aperture area of collector | ||||
| Y3: Flow rate Pump 1 Y3 = Y4 Y4: Flow rate Pump 2 | Matched Flow | Set pump to – Flow rate setting – Flow rate within the entered range and adjusted to the defined collector output temperature | X1: Collector temperature | Y1=0 if X1 > maximum collector temperature [°C] |
| X2: Tank temperature | Y1=0 if X2 > maximum tank temperature [°C] | |||
| X1: Collector temperature | Y1=1 if X1 > X2 + cut-in temperature difference [K] Y1=0 if X1 < X2 + cut-off temperature difference [K] | |||
| X2: Tank temperature | ||||
| X4: Collector input temperature | ||||
| X2: Yield of collector field |