MOD CON BOILER Piping

DKH

Piping a multiple zone wall hung boiler. (Rinnai M series) Primary loop controlled by internal boiler circulator with hydraulic separation with closely spaced tees. (Factory supplied / purchased kit)
Secondary loops and zones (3) controlled by individual circulators.

Do the individual zones also require closely spaced tees? I have seen some "wall hung" boiler piping, no closely spaced tees and also no complete primary loop back to boiler. Not sure how this works. Been piping old-school cast-iron boiler with the boiler being part of the secondary loop and then each zone closely spaced tees with a completed loop back to boiler. Would this be correct for my wall hung, complete loop, isolating boiler with hydraulic separation and closely spaced tees on each zone?
Diagrams would be most helpful.

I hope I explained my questions correctly and any assistance is well appreciated. Thank you

GGross

Sounds like what you are describing is what is called series primary/secondary. I highly recommend that you read through the Idronics no 15 that covers separation in a hydronic system. There are several ways to do this, but it is important to understand the pros and cons.

https://www.caleffi.com/sites/default/files/file/idronics_15_na_2019.pdf

hot_rod

Here are some options. One method is called "horseshoe" the other "moose antler".
Unless you have some high gpm loads, I prefer zone valves with a single delta P circulator.

So off that boiler header a circ with zvs and return to the other side of the header.

psb75

Or, you could do something radical like read the Rinnai M Series boiler manual and go by their recommendations for piping.

hot_rod

Not a lot of guidance in their install manual. What they do have is what I attached above.

The pros here would be better advice.
The boiler man are and should be concerned with adequate flow through their equipment. Beyond that the piping/ zoning options are the installers call.