Quote:
Originally Posted by Drake
So, I have had a chance to see a few hydronic radiant control layout at local retails(DIY and mass market) and see in more detail than pics. On all of them the supply copper size changed from 3/4 to 1" just at the cir. pump loop. Is that to match pump flow? Pump fittings? Manifolds(all where 1")? Copper from heat source was 3/4" in all.
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The manifolds are 1" for manufacturing reasons and for flow reasons. You cannot get equal pressure on all 1/2" spigots if you had, for example, a 1/2" header. The pressure drop would be so much that most of the fluid would go through the first one. If you have only 2 spigots, then a 3/4" header would work but not if you have many more. All the spigots have to "see" an equal pressure (equal supply) of fluid to draw from so you need a big enough cavity in the header that the pressure drop between the spigots is effectually zero.
The supply lines are a different story. They are sized for the amount of heat you need to move and the pumps ability to carry it within its pressure/flow curve. 3/4" piping works for most cases so it has become standard.