Things to know about O2 ingress, corrosion, scale build up in hydronics

hot_rod

The history as I remember it.

Back in the 1980s the availability of inexpensive, flexible plastic tubing made radiant fashionable again. Prior system were copper, bent or welded steel tube systems.

Early tube for radiant was polybutylene, RadiantRoll, and some pp well pipe systems were sold. Pex came later and non barrier was promoted. Finally barrier tube became more mainstay.

The promotors of the tube without any O2 barrier were convinced low temperature radiant would not have serious O2 ingress issues. Regardless of the Euro hydronic industry already having been down that O2 road, and sounding the warning about what we as an industry were about to experience

About 1992 or 1994 Heatway, the major producer of rubber tube, getting a lot of heat (pun intended) about sludge forming allegedly due to non barrier tube, decided to put out a position paper as well as partner with Fernox to bring in conditioners, cleaners, sealer and glycol.

The scale build up section shows how little of a layer of hard minerals can change the heat transfer. Efficiency goes down and the the boiler "skin temperature" increases. This is one cause of failures in thin metal boilers common today.

The information and opinions in this paper are just as relevant today.

Keep the O2 out as best as possible. Know that the DIN standard limits the amount of O2 per day that is acceptable.

Do not fill with hard water, the very first fill with hard water can cause heat exchange compromises.

Also points about the various types of corrosion and typical causes.

Sorry about the quality of the scan, my original is not so crisp. This paper appeared in the large technical binders that Heatway produced over the years.

EdTheHeaterMan

I can breath much easier Bob, now that I have this information about Oxygen.

Thanks Bob!

hot_rod

EdTheHeaterMan said:

I can breath much easier Bob, now that I have this information about Oxygen. Thanks Bob!

As long as you are breathing in and out, we’re in good hands

HomerJSmith

How well do conditioners like Rhomar Pro-tek 922 work in O2 ingress systems with cast iron? Real life experiences, please. I'm about to find out in a couple of weeks.

GroundUp

We've discussed this before, but I'm still looking for an answer. Has anybody ever actually seen a sludged up low temp radiant system caused by non-barrier pex? NOT rubber tube or PB, not leakers with constant crappy makeup water, I'm asking specifically about non-barrier pex causing the sludge.

hot_rod

HomerJSmith said:

How well do conditioners like Rhomar Pro-tek 922 work in O2 ingress systems with cast iron? Real life experiences, please. I'm about to find out in a couple of weeks.

Conditioners need to be put into cleaned systems and blended with good water. Ideally DI or demineralized water. If not you are wasting money on the chemicals. It is a few step process 

The system also needs to be sampled every few years, and boost added if indicated by the test kit

Especially on problem systems, it is not a once and done solution

I doubt the average system owner knows their systems are sludged, corroded, scaled until the heat is off, and or the boiler fails

dko

GroundUp said:

We've discussed this before, but I'm still looking for an answer. Has anybody ever actually seen a sludged up low temp radiant system caused by non-barrier pex? NOT rubber tube or PB, not leakers with constant crappy makeup water, I'm asking specifically about non-barrier pex causing the sludge.

Maybe can ask Thermco about their radiant turf job with white non-barrier Watts pex.
https://www.watts.com/resources/case-studies/new-york-red-bulls (attached article describing in more detail)

and Rehau's Denver broncos turf radiant using non-barrier pex.

Enough time should have passed to be a case study in non-barrier pex usage, especially with extremely long lengths.

GroundUp

dko said:

GroundUp said:

We've discussed this before, but I'm still looking for an answer. Has anybody ever actually seen a sludged up low temp radiant system caused by non-barrier pex? NOT rubber tube or PB, not leakers with constant crappy makeup water, I'm asking specifically about non-barrier pex causing the sludge.

Maybe can ask Thermco about their radiant turf job with white non-barrier Watts pex.
https://www.watts.com/resources/case-studies/new-york-red-bulls (attached article describing in more detail)

and Rehau's Denver broncos turf radiant using non-barrier pex.

Enough time should have passed to be a case study in non-barrier pex usage, especially with extremely long lengths.

Precisely my point. These ridiculously large systems spec'd by the tubing manufacturers as non-barrier says a great deal about how big a farce the oxygen barrier really is. I've never seen any evidence myself, and I've asked thousands of other technicians and "professionals" over a several year period now- not once has anybody ever been able to provide an example. I find it to be akin to the whole dielectric thing where everybody says you need it, but nobody actually knows why. Now to be clear, I always use barrier pex if I'm doing the install- but if I'm working on an existing system that has non-barrier pex, I'm not making a big deal out of it anymore.

hot_rod

GroundUp said:

We've discussed this before, but I'm still looking for an answer. Has anybody ever actually seen a sludged up low temp radiant system caused by non-barrier pex? NOT rubber tube or PB, not leakers with constant crappy makeup water, I'm asking specifically about non-barrier pex causing the sludge.

I installed some non barrier pex systems, all non ferrous components however.
And serviced some non barrier combined radiant/ DHW, online DIY systems.

hot_rod

dko said:

GroundUp said:

We've discussed this before, but I'm still looking for an answer. Has anybody ever actually seen a sludged up low temp radiant system caused by non-barrier pex? NOT rubber tube or PB, not leakers with constant crappy makeup water, I'm asking specifically about non-barrier pex causing the sludge.

Maybe can ask Thermco about their radiant turf job with white non-barrier Watts pex.
https://www.watts.com/resources/case-studies/new-york-red-bulls (attached article describing in more detail)

and Rehau's Denver broncos turf radiant using non-barrier pex.

Enough time should have passed to be a case study in non-barrier pex usage, especially with extremely long lengths.

It does say a heat exchanger is used between the boiler and tubing. Could be everything on the melt side is non ferrous. Why else have a HX?
I can't imagine Rehau signing off on a glycolled system in non barrier, with ferrous components.

Solid_Fuel_Man

@GroundUp

I've worked on a system which was non barrier pex. Water was rust colored and every ferrous component has an orange rust layer in it. This system was a DIY feeding radiant to a new garage. Ironically the garage slab was done with barrier tube. Just the underground between buildings was non barrier. Mixing was done in the house so UG tubing was run at radiant slab temps. System was 3 years old. I was there to advise why circulators kept failing...... 

I told him to dig up the UG and replace it with barrier pex, flush the entire system, run a cleaner for a few days with all circulators running. Flush 2x, and then fill with good water. 

GroundUp

Solid_Fuel_Man said:

@GroundUp

I've worked on a system which was non barrier pex. Water was rust colored and every ferrous component has an orange rust layer in it. This system was a DIY feeding radiant to a new garage. Ironically the garage slab was done with barrier tube. Just the underground between buildings was non barrier. Mixing was done in the house so UG tubing was run at radiant slab temps. System was 3 years old. I was there to advise why circulators kept failing...... 

I told him to dig up the UG and replace it with barrier pex, flush the entire system, run a cleaner for a few days with all circulators running. Flush 2x, and then fill with good water. 

But was it BECAUSE of the non-barrier pex? Or was the water quality crap before that already? Did they stir up some yuck from the existing system and push it out to the garage when it was added? I'm certainly not doubting you, I'm just saying I've worked on dozens of non-barrier pex systems, many of which 20+ years old, and never has there been any evidence of the tubing itself causing any corrosion issues. A couple here and there where there were obvious leaks and makeup water, a couple where they put in used automotive antifreeze, etc which had some definite corrosion issues but the vast majority are clean as a whistle inside, just like the barrier systems usually are. Frankly, I see more corrosion in barrier systems than non-barrier but that's obviously due to sheer volume. I ran a section of my own piping at home in non-barrier just for an experiment about 12 years ago and it's still spotless- even being 170 degrees.

hot_rod

dko said:

GroundUp said:

We've discussed this before, but I'm still looking for an answer. Has anybody ever actually seen a sludged up low temp radiant system caused by non-barrier pex? NOT rubber tube or PB, not leakers with constant crappy makeup water, I'm asking specifically about non-barrier pex causing the sludge.

Maybe can ask Thermco about their radiant turf job with white non-barrier Watts pex.
https://www.watts.com/resources/case-studies/new-york-red-bulls (attached article describing in more detail)

and Rehau's Denver broncos turf radiant using non-barrier pex.

Enough time should have passed to be a case study in non-barrier pex usage, especially with extremely long lengths.

I think that Rehau tube was a special order that was made without the UV barrier as it was covered immediately, not the O2 barrier which is different from the outer UV barrier.