How a Circulator Pump Works in Hydronic Heating

In this short article I explain what hydronic heating with circulator pump is, how it works and what its advantages and disadvantages are. The most important feature of hydronic heating with circulator pump is the use of a pump to transport water in the hydronic heating system. An alternative hydronic heating system is gravity heating.

hydronic heating with circulator pump

In a hydronic heating system with circulator pump, the heating water is forced to circulate in a heating circuit with the help of a circulator pump. The circulator pump can be installed in the flow pipe (FP) or in the return pipe (RP). However, it has become generally accepted to install the pump in the flow pipe. If you can’t imagine a circulator pump, you will find a modern circulator pump in Fig. 1.

Function of hydronic heating with circulator pump

For the function of this type of hydronic heating, the heating water is transported by using a pump. In the first step, it is heated in the heating source and then pumped into the heating circuit by the circulation pump.

It flows via the flow to the radiators and returns via the return to the heating source. As long as the pump is in operation, there is a permanent circulation and thus a circulation of the heating water in the heating circuit (see sketch of the diagram of a hydronic heating system with circulator pump).

Advantages and disadvantages

Advantages of a circulator pump

In contrast to a gravity heating system, the hydronic heating system with circulator pump has several advantages, for example, radiators can be placed further away from the heat generator or can be located below the heat generator. This means that with a hydronic heating system with circulator pump, the heat generator can be installed anywhere in the building, for example in the attic.

Further advantages of a hydronic heating system with circulator pump are smaller pipe cross-sections and thus lower pipe costs. As a result, there are fewer line losses, less heating water is required, and thus the heating times of the heating water are also shorter.

However, one thing is mandatory: when installing a hydronic heating system with circulator pump, hydronic balancing is necessary to ensure proper operation of the system.

Tip: Here you find more information about hydronic balancing.

All the advantages are listed here once again:

• Small nominal diameters of the pipelines and thus lower piping costs
• Lower water volumes and thus faster heating of the heating water
• Inert system and good controllability
• Arrangement of the radiators is arbitrary
• Arrangement of the heat generator is arbitrary

Disadvantages of hydronic heating system with circulator pump

A major disadvantage of this type of hydronic heating system is the necessary power supply for the circulator pump. However, this disadvantage plays a minor role in Europe.

For this reason, I see the biggest disadvantage as being the mandatory performance of hydronic balancing, which, however, is usually forgotten, neglected or not even considered in existing buildings, for example when converting from gravity to heating system with circulator pump.

A lack of hydronic balancing leads to flow noise in the heating network, unintentional short circuits, so that areas of the building are overheated or undersupplied, and suboptimal flow behavior of the heating water.

Here once again listed all the disadvantages:

• Electricity connection for the circulator pumps is mandatory
• If hydronic balancing has not been done, there will be problems in the heating network
• Flow noise in the heating network as well as pump noise
• With stage-controlled circulator pumps, the share of the total power consumption is relatively high (can amount up to 5% of the total consumption) – see article “7 reasons for replacing the heating pump”.

Conclusion

Due to the advantages mentioned above, today’s hot water heating systems are almost exclusively planned as hydronic heating system with circulator pump and gravity heating systems are converted to systems with circulator pump. Only in remote areas without power supply the use of a gravity heating system is still reasonable.

I hope this article helps you to understand a hydronic heating system with circulator pump a bit better. If you have any questions I’m looking forward to see your comments

Best regards! Martin

Further links and sources:
Wikipedia – Circulator Pump
Das große Pumpen 1×1 von Fristam
Wilo Pumpen
Grundfos Pumpen