It's not that the zones don't match. The temperature difference I'm fretting about (maybe unnecessarily) is across the hydraulic separation —i.e. closely spaced tees— between boiler pump and zone pump.
From my observations it seems a good portion of the hot water supply coming from the boiler
isn't getting out into the house. It is just going straight back to the boiler
In this picture, the upper grundfoss pump is on the primary loop to and from the boiler return and supply. The green taco pump at the bottom is pumping out to the house and that water returns to the closely spaced tees.View attachment 78873
And here, in a close up, is the specific issue that I'm having. The water being sent out to the house is often no hotter than the return on the primary loop.View attachment 78874
(In this example there is a drop between 90F and 88F. But often there is no difference.)
What I wonder is whether all of the water heading into those closely spaced tees is mixing, and then half is going to the return and half is going to the house.