Good afternoon, dear guests!
If you carefully read the information on the Internet, then most experts convince us that the most correct installation of a circulation pump is to the return line, explaining this by the fact that in the return flow - the temperature is lower than in the supply and the operation of the pump takes place in a more gentle conditions.
But, if we study the original source (instructions for the pump), we will see that the circulation pumps are designed for a temperature of +110 ° C, and in our heating systems +90 ° C is already the limit.
In other words, modern units can easily withstand the high temperature of the supply line (even with a margin), but until now we can meet experts who reject such schemes.
In fact, such pumps are designed to ensure the forced movement of the coolant in a closed loop, - and the provision of movement can be carried out from any point of the closed loop and is a fundamental factor for choosing the place of installation of the pump is an serviceability.
If you take any pumping group of the boiler unit from Meibes or Oventrop, you can see that in these nodes the pumps are always located on the delivery, and this is a number of those manufacturers who "will never advise bad".
The only feature is related with solid fuel boilerswhich lack the necessary automation. Since there is no possibility of an abrupt stop of fuel combustion, when the coolant boils, steam is formed, which enters the pump through the supply line. And since the pump is not designed to work with steam, the circulation stops, and the coolant is abruptly vented through the emergency valve.
This is the only case where the circulation pump must not be installed on the flow line.
In addition to ease of maintenance, there are several more requirements for installing a circulation pump:
1. The shaft axis with a wet rotor should be installed strictly at a horizontal level in order to avoid the formation of air pockets, and, accordingly, to increase the service life of the device parts:
2. Installation of the pumping unit should be carried out immediately after the expansion tank in the direction of movement of the coolant.
3. Installation of the pump is carried out on the flow - to all consumers or on the return - after them, but not between them.
In fact, there is absolutely no difference in which direction the circulation pump is being installed, but when installed between consumers, parasitic circulation flows are created (in the illustration, red arrow).
It is known that a working impeller creates a zone of reduced pressure in front of itself, and this zone will be take away the heat flux (indicated by the red arrow) from all radiators, thereby creating parasitic fluxes circulation.
Thus, the radiators located in front of the pump will always be cold.
Conclusion: If the temperature in the heating device can rise to vaporization (which is dangerous), then the circulation pump installed only on the return line, otherwise the direction of installation does not matter and is selected for ease of maintenance.
I would be glad if the article was useful to you!
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