hePEX Primary Piping

johntrhodes81

Is piping the primary connections to manifolds, expansion tank, etc out of hePEX a bad idea? As long as there is 18" of copper or metal tube from the boiler?

Thanks,
John

SWEI

Not a problem as long as everything is sized and supported properly. Getting tee branches and short runs of PEX to stay level and plumb can be a bit of a challenge.

hot_rod

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 )

Tinman

Copper and steel for me too.

Solid_Fuel_Man

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

SWEI

I heard manifolds and assumed PEX downstream. If there's a CI boiler and a mixing valve, hard pipe to the mixing valve.

johntrhodes81

Mod-con boiler -> Manifolds -> Pex-AL-Pex -> CI Radiators.

SWT between 120 (60 outdoor) and 180 (0 outdoor).

John

SWEI

Temps seem high to me, most especially at the low end. How were they determined?

NY_Rob

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.

jonny88

Steel on mod con definitely use Dirtmag .You would be surprised what they pick up actually rather them on all miscons.

SWEI

...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.

kcopp

I have done it a time or two... Although I will prob not do it again now that I have a propress tool. I did this install just before Christmas a few years bac and was pressed for time as there was no heat or hot water in the home.
No issues what so ever... The system was cleaned and treated w/ Fernox

Rich_49

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 ?

NY_Rob

kcopp said:

I have done it a time or two... Although I will prob not do it again now that I have a propress tool. I did this install just before Christmas a few years bac and was pressed for time as there was no heat or hot water in the home.

No issues what so ever... The system was cleaned and treated w/ Fernox

I'm taking notes on the circulator to hot water tank mounting in your 2nd photo... is that kosher?
That would save me some work on my install...

johntrhodes81

I was thinking about using HePEX between the manifolds and the boiler, but decided to scratch that and stick with copper. Rich has been very helpful, I really appreciate it. Yes the envelope needs work. Uninsulated Concrete block exterior walls loose a lot of BTU's fortunately the house has alot of radiator capacity.

John