The circulation pump should be preceded by a multi-pole contact breaker in the fixed installation.
Dimensioning, Pump Capacity diagram
Example: Start with the heat output of the boiler (e.g. 40 kW) and move horizontally to the right in the diagram to the chosen Δt (recommended by boiler supplier), which is the temperature difference between the riser from the boiler and the return to the boiler (e.g. 85°C - 65°C = 20°C).
Move vertically up to the curves representing load unit performance. Check that the pump curve overcomes the additional pressure drops in system components such as pipes, boiler and storage tank.