Best Of
Re: proper supply and return piping to my indirect
you can get 10 gpm through 1” copper M in a short length and stay under the 4 fps rule.
But you need at least 100,000 btu of boiler to make it worth flowing that gpm. What size is the boiler that will run the indirect?

Re: Heating & Cooling Calculations & Equipment
On the A/C side I advise Smaller is better. An Oversized system will never be proper 100% of the time, an undersized system will be only wrong maybe 1 or 2% of the time.

Re: Pressuretrol
It's probably fine. If it runs at .4 psi on a normal call for heat and the pressure rises during recovery from night setback this is completely normal.
You should leave the 3 psi gauge shut off anyhow unless you are checking the pressure.
The pressure control scale are usually inaccurate.
You can try and adjust it.
If you loosen the adjustment too far the inside mechanism may become disconnected
Re: Enough boiler ?
Gosh, if the system is working well, to your wants and needs, no need to make it more complicated.
Boost on most boiler would enable if the boiler is falling behind the load, while controlled by outdoor reset, boost allows the boiler swt to rise up a certain degree amount to try and help cover the load. On my Lochinvar Knight the boost increase is adjustable.
You would need a seriously large load for a normal operating system to want to go 20° over normal SWT.
If your ODR is set to 119, and for some odd reason you took 20 steps at 1° that would be 139° SWT.
Perhaps the over-head door is left open on a cold day? you might see the boost run all the way across the 20 steps?
Or if someone closes the garage door and the system catches up without needing to use the boost :)
At the flow rate you are running it would take a very long time to elevate that slab to 165 or any temperature that would shock it, remembering you have nearly 1/2 million lbs of concrete to work against.
I imagine it would catch the load and shut down way before you hit 165, or even 139 slab temperature.

Re: Oil Boiler Issues
And if you try to learn by watching YouTube, even some pros don't start by showing the reaming. They start with the flare tool.
There's an old saying that applies to many trades. Proper preparation prevents poor performance...

Re: One year old boiler repiped
Yes..it is made by WM...vg boiler with 3" Tappings which is nice. Mad Dog
Re: Drip to nowhere.
If it were me, I would have my hammer in hand, plus a prybar, a small saw to cut the lath, and the shop vac to clean up the mess. Get busy and tear into that wall. No amount of guessing is ever going to come up with the answer of where that pipe goest and does it do anything. My guess is that it runs down the wall a ways and then is simiply capped off. Maybe it was used for something at sometime in the past, but my guess is that it is presently doing nothing at all. On the other hand, if it is connected to something…. or disappears under the floor, you need to deal with it and the sooner the better. This is not going to be a big project, just a minor annoyance and you will be so happy once the riddle is solved.
Keep us posted, these riddles are great fun.
Re: Proposed Piping Layout
A great application for a hydro sep.
The sep would give you air, dirt, magnetic, and hydraulic separation in one device.
Your loads are now in parallel so the get the same temperature.
In your drawing the loads are in series and will get a different blended supply temperature

Re: How Does This Look?
Your work is Stellar...neat as a pin..Great soldering job! Mad Dog