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Circulator placement for a primary loop, supply or return?

Firstly, the circulator(s) should be drawing away from the expansion tank connection point.

In most primary/secondary setups I see the boiler being "pumped into" and the secondary pumping away. The reason that one might put the circulator on the inlet side of the boiler is the internal pressure drop of the boiler. Many, especially those with Giannoni heat exchangers, have small water tube areas and high pressure drops. You do not want to impose a pressure drop on the suction side of your circulator if you can help it. Flashing and cavitation can result.

That all said, set it up with each pump drawing from a common point (such as a low loss header can provide) and all should be well.


  • Tony_46
    Tony_46 Member Posts: 1
    Circulator placement

    I've seen circulators placed on the supply side or return side of a primary loop on various Mod/Con boilers.
    Does this make a difference.
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