Pex without o2 barrier used in radiant floor

Jack, CVMS

Forgive me for jumping in late, but I just discovered this forum tonight... And glad I did - a lot of good information here.
Regarding the tubing being used: To the inexperienced purchaser, the idea of larger tubing working at twice the spacing had to have sounded like quite a deal. But Wirsbo (the only pex I will use) maintains that 5/8" won't supply enough more heat than 1/2" to make it worth while. So I doubt that 3/4" is going to do much better - and the concrete certainly won't conduct well enough to cover the gaps. Someone got sold a bill of goods, but we've all seen that, haven't we?
On a slab on grade (Alaska climate) I'll start next to the wall with 6" spacing, then go to 9" at one to two feet, 12" spacing for the next two feet, then widen the spacing to 24" if the floor is large enough. Variable spacing works well up here, and saves a few feet of tubing on large jobs. Too many DIY'ers (and some contractors) have no concept of the theory of radiant heating, and oversize the tubing, ignore equal loop lengths, and couldn't care less about temperature drop through the loops. And it's pretty difficult to go back in and redo it once the slab's been poured. And even when you can straighten out someone else's mess, most customers don't like to hear that it will cost them almost as much to have it done right the second time as it cost to have the system installed wrong the first time.
Have seen non-barrier systems with ferrous metal boilers. Pinholes in Extrol tanks, leaks in fittings, gunk in the fluid, and boilers rotting out from the inside... Not pretty.

Alan Williams

pex without O2 barrier

I am watching a radiant infloor heat job being installed. I did a quote for this job but the owner deceided to save money so he is laid the pex by himself and another contractor is installing the boiler.
I spec'd 1/2" pex w/O2 barrier on 12" centers. He went to another supplier who sold him 3/4" Potable water pex without O2 barrier and told him to install it on 24" centers.
The heating contractor is not using a heat exchanger between the pex and the boiler.Isn't he asking for trouble? I was told you could not do it that way without ruining the boiler.
I am friends with the owner and I hate to see him have problems that he could have avoided.
Is it all right and I am the one that is wrong?

[Deleted User]

your not wrong,,,

the boiler will be toast in short order...friend or not,,if he didn't want to listen to you,,,well,,,oh well..

kevin coppinger_4

I t will end up....

costing him big time in the long run...Was there a design done? 24" o/c will give very un even heating. Is the boiler Cast iron? Is every component NON-ferrous? What is the tubing brand HE is using? Do yourself a favor and let your friend get some advice from another contractor(3rd party)Not much of a friend if he doesn't trust you....Is this in a slab install? Only one chance to do it right....kpc

Justin Gavin

It really depends on the boiler and trim

Well the whole O2 thing really applies to the type of boiler.

If the boiler has a cast iron or steel heatexchanger in the boiler then he will be screwed.

If the boiler is a copper Fin or Stainless Steel than he wouldn't really need the O2 barrier. The O2 barrier stops Oxygen from penetrating the PEX. If it penetrates the PEX it will affect the ferrous types of metals.

Now with that said. 24" on center is not common in any residential system I ever worked on, and would probably not be as comfortable as 12". But I live in Wisconsin where winters are fierce. If you live in a mild climate the spacing might work. I ccouldn't give you an educated guess on that.

Also one more thought, if anywhere in his sytem he has black iron (ie between the fittings, unions, or nipples than O2 is needed because the fittings will rust and clog the small passages used with copper fin and/or stainless steel boilers.

Hope this helps.

Thanks,

Justin

Earthfire

friend?

Not much of a friend if he would believe strangers over your good advice. Probably will be your fault when the problems start. You told him about radiant didn't you! Find a new friend, it'll hurt less in the long run. Been there done that!!!

hr

He may be fine

The heat loss calc will tell if the 3/4 on 24" center will meet the load. 2 foot is wide for residential, as you will feel cool spots on that wide spacing.

I'm currwently doing a 10,000 square foot store with 3/4" non barrier. It is on 12" centers, however.

This is a one temperature, 2 zone slab system. I will use a stainless boiler and bronze pump. Copper piping everywhere else. Really no different than an open domestic hot water system with a recirc pump.

If there is nothing to corrode, then O2 through the tube really isn't an issue. O2 ingress is fairly low at low slab on grade temperatures.

When you start talking 12,000 feet of tube the cost difference between barrier and non barrier does add up. This job was bid PAP, and non barrier. Around here PAP is double the non barrier "commity" plumbers pex. Also readily available, locally. Shipping alone on 12,000 feet of tube is a big number these days.

hot rod

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Alan Williams

Pex without O2 Barrier Update

This was not residential install it is a comercial store, in slab. But he is using a cast iron boiler and black iron pipe for the near boiler piping. I have kept my mouth shut up to this point.He hasn't put any water in it yet so he still has time to use a plate heat exchanger in the system. I am going to tell him tomorrow about it. If he gets mad so be it. I will feel better knowing I tried to help him avoid major problems. Thank you everyone for your imput.

George_10

You might suggest cleaning and treatment

Your friend would be well advised to have the system cleaned and prepped before putting into service. Then it should be treated. Since this is our product area, advise him to look at our web site. The photos of poorly treated components or non treated components will make the point for you. If he doesn't listen to you, he will see his so-called savings go up in smoke in repairs and irritation.

I also wonder about a friend who listens to a stranger over a friend.

JohnNY

I thought that...

the jury was still out as to the significance of the 02 barrier. Isn't it accepted or declined on a per-case basis?
I, personally, always use the barrier type because in NYC we rarely get to do high footage jobs. A bathroom here, kitchen there. The difference in cost of the tubing is NEVER the big issue.

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