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[slimjim]

This is a great place to do just that isn't it, I will have to check out the site.

[Sprinter]

Oxygen barrier or O2 pex has an extra layer to prevent oxygen diffusion into the system. The only time you would not need the oxygen barrier is when the system does not contain ANY ferrous metals, like the new mod-con aluminum or stainless steel heat exchanger boilers and all emitters are pex,Aluminum, copper etc. by using O2 pex you are reducing the amount of exposure of air that will be introduced into the system and eliminating corrosion issues. On an open system how much water is actually exposed to the air directly, now add to that every inch of non barrier pex. Obviously the pex permeates and introduces much more oxygen. Your headers like primary secondary piping and distribution supply and return manifolds are done in copper or black iron pipe which is an oxy barrier.

What makes high mass radiant so good is the ability to emit large amounts of heat with a very wide range of water temps and low flow. Fan coils & fin tube for example drop off dramatically as soon as supply drops below 160. This ability offers much more efficiency and much more evenly heated comfort options if you choose to. I mean there is a good reason these rads are in demand, just look at pex supply for pricing on new versions of Buderus radiant panels and the Runtal panel rads and the install and control options. PM mag online has some good info on using rads and installs. It will be a real nice project.

Constable, noisy rads can be from large temp swings or very quick temp swings. Possible excess flow, too high supply temp, in a very drafty place then being hit with 160 plus water. The sections moving.

Frydaddy, could be several possibilities, but with your boiler I see there, first thing I would think is lack of flow or lack of emitter transfer. I mean if your boiler never shuts off , running flat out and supply temps drop as the outdoor temp drops, then I might say the boiler isn't big enough.  Proper circulator sizing and flow are one of the most common issues.

[Sprinter]

Here are a couple manifold options if you choose to individually control each rad. An injection type and a variable speed on demand with outdoor reset mixing valve control, then multi temp zones individually isolated.

[ffbare]

  nice pictures

[Pinehouse4]

Thank you Sprinter, I will study the manifolds. This morning it was suggested to me by the owner of the local rental equipment location and well/pump specialist that I use a " pex manifold " of the type used in radiant floor heat with the valves attached, having the wires from the thermostats all come back to a central location.. Just his thought, one of a  number I need to sort out.

I see now why you suggest the oxygen barrier pex.

Bob