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Posted by Mark Stelter on September 19, 2006 at 01:28:51:
I'm installing a condensing Weil-McLain Ultra boiler which utilizes a primary/secondary loop system. I've been trying to get into my head the purpose of the primary loop and why the installation instructions limit the horizontal distance between supply and return to 12". It seems to me that Weil wants some recirculation but why? This mixes some hot water with the cooler return water before sending it thru to be heated. The greatest potential for heat transfer would be with the coolest water.
To add to my confusion, this primary loop is shut of when there is a call for domestic hot water.