How to choose a heating circulator pump
The circulator is the heart of every heating system: it moves hot water between the boiler and the radiators (or underfloor loops). Choosing it well means steady comfort and lower bills. Here are the four parameters that matter.
1. Flow (m³/h)
The amount of water moved per unit of time, driven by the system's thermal output: as a rule of thumb, about 0.86 m³/h per 10 kW at a 10 °C temperature difference. A typical flat needs 1–2 m³/h.
2. Head (m)
The circulator's "push" — how well it overcomes pipe resistance. Residential systems need 4–6 m; larger or underfloor systems 6–8 m.
3. Connection (DN)
Must match the existing pipe: DN25 (1½") and DN32 (2") are the most common. Check the port-to-port length (130 or 180 mm) for a direct swap.
4. Efficiency (EEI)
Modern electronic wet-rotor circulators vary speed automatically and reach EEI ≤ 0.20, using up to 80% less energy than old 3-speed models.
Which Grundfos model
For homes, the Grundfos ALPHA range is the standard: quiet, efficient, with a display. For commercial systems, MAGNA3 offers more head and BUS communication.
Not sure? Use our pump selector: enter flow and head and we show compatible models on the curve. Or go straight to heating pumps.
Häufige Fragen
What head does a domestic circulator need?
A typical residential system needs 4–6 m of head; underfloor or larger systems reach 6–8 m.
Is it worth switching to an electronic circulator?
Yes: a variable-speed electronic circulator (EEI ≤ 0.20) uses up to 80% less energy than an old fixed-speed model, paying for itself in a few years.