The
installer got a great price on a “contractor pack” of 3/4-inch copper tees, so
the supply and return manifolds are built with 3/4-inch copper, as are all the
zone circuits ...
As it exists, this system works relatively well, but it could be further refined. See if you can spot some design details that would provide equal or better performance while using less hardware.
Overview: An installer has decided to use a mod/con boiler with a high head loss characteristic and connects it to the rest of the system as a secondary circuit with its own circulator. The two load circuits require the same water temperature, so he connects them as shown.