Best Of

That's not entirely true.

Some ice can be denser than water.

However, I am curious what some experts would say in regards to O2 being able to get through a material where water does not. Especially if the water is under slight pressure. All of this is way above my paygrade.

Did you look at the board? A relay like that is rated for millions of operations, even like 10 cycles an hour is nothing for that type of relay. Usually problems with relays in that application are that the solder fatigues and cracks where it is soldered to the board.

@LRCCBJ Said: I would not spend the time to put the circulators on the supply side. It's a day's work and it is not going to improve your situation a significant amount. 

I disagree with not improving the system. I had a customer with a Monoflo® system. We were always having problems with air bound radiators because the auto vents on each radiator were not working. So I would need to show up twice a season to help the homeowner with the air bleeding process and drain the expansion tank. When it was time for a replacement boiler, I located the circulator pumps on the supply side after the PONPC that was also on the supply side of the boiler……. Never had an air problem after that!

So if @JWieg727 is going to change the near boiler piping anyway, then why not create the best air removal location in the system. The hottest water at the lowest pressure. With the circ pumps on the return, that place does not exist. With the circ pumps on the supply and the PONPC just before it on the supply, you have the best air removal system built into the design of the piping.

There were some old style ball valves that had a screwdriver slot to open/close them. You can use ball valves for balancing, you just have to understand the correlation to the handle position is very much not linear. You can't use gate valves for balancing, they must be fully open or closed or the gate will vibrate in the flow and destroy the threads on the stem.

If the circulators are always both running at the same time then you don't need the flow checks(not sure why they did that, the reason to have 2 circulators would be to be able to zone the system). You do need to balance the 2 loops so that it will heat evenly(or change the control so it does run each loop off a separate thermostat).

You could add another loop for the problem loop or the regular tees and balancing valve would probably be ok even though it would decrease the overall flow some.

See how the tube end of this npt to crimp adapter is much smaller than the npt end, this type of fitting will restrict the flow too if this is the type of fitting you are using:
https://www.supplyhouse.com/Bluefin-PXM075-DZR-3-4-PEX-x-3-4-NPT-DZR-Brass-Male-Adapter-Lead-Free

I think there is more going on than absolute molecular size and the state of matter can have an impact on diffusion. Water is a liquid and thus bound together by intermolecular forces whereas oxygen is a gas and not bound together by any significant intermolecular forces.

"Water osmosis its way out?" Probably can't because a water molecule is too large.

You'd best believe that oxygen and osmosis really is…"a thing."