Heating

Circuits

Circuits shows the basic hydraulic layouts, from throttling to injection with fixed premixing. The symbols follow DIN EN 1861. Each circuit has a short note on where it is used, its properties and how it works.

ConsumerV var · T festMVL 70°RL 40°Flow controln~

FlowReturndashed: variable flown~ variable speedconst constantM motor actuatorT sensorcheck valve, tip toward inletSymbols to DIN EN 1861

Use

  • Radiators, underfloor heating, single zones.
  • Cooling coils and ventilation without a frost risk.
  • District heating, condensing boilers, buffer tanks.

Properties

  • Flow varies in the whole circuit, supply stays at the source temperature.
  • The return falls with the load. Suits condensing boilers and district heating.
  • A header with differential pressure, or a pump of its own. Variable-speed pump.
  • No supply-temperature sensor. Air heaters can freeze.

Function

The valve throttles the flow. Less water, same temperature, less output.

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How it's calculated

Circuits shows six basic hydraulic layouts with the symbols of DIN EN 1861. The notes cover where each is used, its properties and the roles of valve, pump, consumer and check valve. There is no numeric design on the page. The worked figure is the mixed temperature of an injection mix, using the same energy balance as the mixed-temperature calculator.

Worked example

Mixing 6 l/min at 70 °C with 4 l/min at 15 °C: flow to the consumer at 48.0 °C.

FAQ

Which circuits are included?
Throttling, mixing, injection with a two-way and a three-way valve, diverting, and mixing with fixed premixing.
Do the symbols follow the standard?
They follow DIN EN 1861 for pumps, valves, consumers and the direction of flow. They are not a fabrication drawing.
How is the check valve drawn?
The tip points against the blocked direction, towards the inlet of the flow it stops.
Does the page calculate the flow?
No. That belongs to heating pipes, heat output and mixed temperature.