hePEX Primary Piping

what temperatures would you be running?

I'm wondering about long term effects of non or less that 100% oxygen barrier tube in high temperature hydronics. Are any of the fusion well PP pipes O2 barriered?

I don't recall many sludge and corrossion issues with boilers, pumps and components until we introduced plastics into the installations?

Guess we will know in 5-10 years like the PB and early rubber tube installations. Are we tempting fate?

I think copper and steel are still the best near boiler piping products. Maybe I'm just getting old )

the higher the temperature the more oxygen can pass into the pex, as HR said less than 100% is something, I think it depends on the amount of Ferris metals that can take the "hit" to rid the system of oxygen. Take a mod-con with a stainless HX and a bunch or radiant pex, with an iron circulator and a steel expansion tank there is little else to oxidize and I think we will be seeing those systems eat through the thin expansion tanks in the next ten years. A far cry from CI radiators and boilers piped with 100% closed copper pipe.

SFM

I just had to make the same decision- pex or metal for near boiler piping on my new mod/con system.
Decided to go with copper/black pipe up to the manifold after the CH pump- then OB PEX A to the zone valves and out to my existing 3/4" copper baseboard lines.
For the return I'm using OB PEX A from existing 3/4" copper baseboard right up to the return manifold and copper from the manifold to the boiler.
For the indirect DHW heater- all copper to/from the DHW circulator/boiler, but non-OB PEX B for the DHW to house domestic water lines.

It's tempting to use PEX for closer to boiler connections- especially when a two dollar PEX connector replaces a twenty dollar brass union. But, I like the idea of being able to stabilize the circulators, Spirovent, expansion tank, etc... to kindorf and know it's not moving vs. less stable mounting going mostly PEX.

...and be sure to flush/purge thoroughly before the new boiler and circ are installed. We use a 20µ cartridge filter on the return line to the purge cart and you wouldn't believe the crud that comes out.

House is a mix of Cast iron rads and CIBB .; Heat loss performed , room by room . House has some issues and the temps stated to be required were determined by me based on the parameters given me by John . Made some recommendations , they were listened to but not agreed to for various reasons . For the system to work and John and his family to be comfortable the curve is as stated above . Does that answer how the temps were arrived at ? Good lookin out though Kurt . Temps will be able to come down when further work is completed on the envelope .

John , could you please clarify where it is that you want to use HePex ?