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[cando attitude]

Well, I'm slowly but surely making progress on the install of my new Portage and main 28-40 and I am in the market for PEX at this point and wanted to throw a few questions to you guys who know a whole lot more than I do.  A little about the install: approx. 75' run (Thermopex Brand) of pipe.  In the house, I have a single heat exchanger coming off the air handler and I plan to install a DHW heat exchanger (still trying to decide if I want sidearm or plate-frame).

Questions:
1.)  With corrosion inhibitor in the fluid, is there really a need to buy O2 pipe?
2.)  Does the thermopex pipe that I purchased have an O2 barrier?
3.)  The boiler itself is open to atmosphere and thus is exposed to O2 as well.

By the way, here's a picture of the angst I went through getting the boiler in place

Help!!

[Jwood]

Uponor HePEX is what I'd use.

[CountryBoyJohn]

No need for O2 barrier pipe. Also, I would recommend a plate exchanger over a side arm all day! Easier to install! They only way I would recommend an arm is if you have low usage. Plumb in the 20-plate before your tank and enjoy unlimited hot water!

[RSI]

1.) No, there is no need for it.

2.) Yes, Thermopex has oxygen barrier. (only way that type of pipe is made)

3.) Doesn't look like a question but I agree with it. 

[LittleJohn]

CANDO, the only time you need to run pipe with an O2 barrier is if you are running a closed loop system; because you are trying to limit the amount of O2 that gets absorbed thru the walls of the pipe and into the system.

This is not say that you can't run an O2 barrier, and be fine (...you would be); but most people don't want the extra expense of barrier pipe.

[woodbutcher]

I used CB's pex on my CB model CL400 boiler when I purchased it and it did not have the oxygen barrier and it failed in 6 years. The new thermpex  that was a replacement for the old pex has an oxygen barrier and it has been in use for over 8 years and no failure. When I replaced the old pex it was as brittle as glass. This has been my experience with pex. I think it is better to go with the oxygen barrier from the start than it is to replace it latter on.   

[cando attitude]

I appreciate the responses guys.  Thanks for the help.  I'm looking to run my inside lines this weekend, hook up the heat exchanger in furnace and perhaps fire the girl up sometime on Sunday.

On he DHW heat exchanger, I think I've convinced myself to go with a plate type before the water tank.  My gut tells me to go with a 30 plate but I'm also wondering if this is overkill and if a 20 plate would work.  The way I see it, the DHW HX should see incoming hot water around 180 degrees.  I'm hoping to get hot water around 130F.

[RSI]

20 plate will make all the hot water you want but may require a larger pump to do it. The 30 will have lower head pressure which will give you more GPM. If the pump is just barely big enough for your system, I would go with a 30 plate.

[RSI]

I used CB's pex on my CB model CL400 boiler when I purchased it and it did not have the oxygen barrier and it failed in 6 years. The new thermpex  that was a replacement for the old pex has an oxygen barrier and it has been in use for over 8 years and no failure. When I replaced the old pex it was as brittle as glass. This has been my experience with pex. I think it is better to go with the oxygen barrier from the start than it is to replace it latter on.

Being non barrier was not the reason for the failure. Without seeing it I couldn't say what caused it to fail but if it was the same brand with barrier and handled, installed, etc the same way it would have failed too.