Premature Failure of Hayward H250ED2C

[mas985]

That particular heater model is supposed to have a cupro nickel heat exchanger (all H series Haywards do) and from what I understand should not turn green like copper does so maybe the tubes are copper but perhaps only the fins are cupro nickel?

I have a 18 year old Hayward H400IDL heater with a SWG pool and no issues although I have never taken it apart either.

 

[MarkHoop]

Can you cut out a section of the copper tube and show the inside?

Can you show the whole heat exchanger?

Sorry, the HX and heater all still functioned normally when I closed the pool so no destructive examination is possible. Need to replace the bypass valve and components for sure and maybe bottle brush the HX tubes?

 

[JamesW]

Natural gas produces a lot of carbon dioxide and water as part of the combustion process.

Maybe the flue gasses are not exhausting correctly causing excessive CO₂ and water to circulate around the heater which causes corrosion.

Airborne sulfur compounds also can cause problems.

Maybe dry acid dust is getting into the air from the pH down being stored nearby.

Why does copper turn green?

The chemistry behind copper patina

www.science.org.au

 

[JamesW]

The tubes might be standard copper.

Even if they are cupro-nickel, they are still mostly copper and I would think that they can corrode just like copper.

They might be slightly better, but I don't think that they would be a lot better.

https://hayward.com/media/akeneo_connector/asset_files/L/I/LITUHSBRO23_Universal_H_Series_Brochure_DIGITAL_4ce2.pdf

 

[JamesW]

Cupronickel should be silver, but the heat exchanger looks like copper color.

Cupronickel or copper-nickel (CuNi) is an alloy of copper that contains nickel and strengthening elements, such as iron and manganese.

The copper content typically varies from 60 to 90 percent. (Monel is a nickel-copper alloy that contains a minimum of 52 percent nickel.)

Despite its high copper content, cupronickel is silver in color.

Cupronickel is highly resistant to corrosion by salt water, and is therefore used for piping, heat exchangers and condensers in seawater systems, as well as for marine hardware.

Cupronickel lacks a copper color due to nickel's high electronegativity, which causes a loss of one electron in copper's d-shell (leaving 9 electrons in the d-shell versus pure copper's typical 10 electrons).

Cupronickel - Wikipedia

en.wikipedia.org

 

[MarkHoop]

The tubes might be standard copper.

Even if they are cupro-nickel, they are still mostly copper and I would think that they can corrode just like copper.

They might be slightly better, but I don't think that they would be a lot better.


View attachment 536008

https://hayward.com/media/akeneo_connector/asset_files/L/I/LITUHSBRO23_Universal_H_Series_Brochure_DIGITAL_4ce2.pdf

Ok, here's another thought....with the bypass valve being broken (no idea for how long but clearly it disintegrated , see pic) the incoming water is not being forced into the HX and as such can just freely exit through the outlet. Do you see any issues with:
1 - backflow from the SWG or Cl concentration due to the lack of flow in the heater
2 - other issues caused by less than optimal flow through the HX?

 

[MarkHoop]

Although this does not explain the rapid destruction of the bypass valve components...

 

[JamesW]

 

[JamesW]

Excessive temperatures in the HX can cause accelerated corrosion in a corrosive environment.

 

[JamesW]

If the copper does contain nickel, the percentage would probably be low due to the fact that the copper does not look silver.

Maybe the percentage is 10% or less.

Maybe it is only 1% and that is enough to call it Cupro-nickel?

"2.1 Physical properties

Nickel has a marked effect on the color of Cu-Ni alloys.

The copper color becomes lighter as nickel is added.

Alloys are almost silvery white from about 15% nickel.

The luster and purity of the color increases with nickel content; from about 40% nickel, a polished surface can hardly be distinguished from that of silver".

Copper-Nickel Alloys: Properties, Processing, Applications

Cu-Ni alloy booklet from DKI German Copper Institute

www.copper.org

Fun fact: U.S nickels are made of cupro-nickel with 75% copper and 25% nickel.

 

[MarkHoop]

Maybe dry acid dust is getting into the air from the pH down being stored nearby.

Perhaps but that might be a stretch as I really don't keep many chemicals and those that I do are tightly sealed due to grandkids

 

[JoyfulNoise]

Sodium bisulfate is NaHSO4. When it dissolves in water you get sodium ions and hydrogen sulfate anions (HSO4-). The hydrogen sulfate anion is acidic as it further dissociates in hydrogen ions (acid proton) and sulfate (SO4(2-)).

Sulfates are known to cause advanced corrosion of all kinds of ferrous alloys as well as galvanized steel through processes like crevice corrosion and pitting oxidation. Neither of those processes require an external current or driving source - the corrosion proceeds through the redox reactions of ferrous and ferric iron atoms (Fe2+/Fe3+).

Sulfates also increase the solubility of the transition metal coatings on SWG plates and causes increased wear of the catalyst layer (ruthenium metal).

 

[MarkHoop]

Sodium bisulfate is NaHSO4. When it dissolves in water you get sodium ions and hydrogen sulfate anions (HSO4-). The hydrogen sulfate anion is acidic as it further dissociates in hydrogen ions (acid proton) and sulfate (SO4(2-)).

Sulfates are known to cause advanced corrosion of all kinds of ferrous alloys as well as galvanized steel through processes like crevice corrosion and pitting oxidation. Neither of those processes require an external current or driving source - the corrosion proceeds through the redox reactions of ferrous and ferric iron atoms (Fe2+/Fe3+).

Sulfates also increase the solubility of the transition metal coatings on SWG plates and causes increased wear of the catalyst layer (ruthenium metal).

Ok, so that is the sulphate issue but would you not think that in order to create the current situation and in order to have that much of an excess in sulphates that the pH would test out at very low? If not using sodium bisulphate to lower pH what is the preferred addition?

 

[JoyfulNoise]

Ok, so that is the sulphate issue but would you not think that in order to create the current situation and in order to have that much of an excess in sulphates that the pH would test out at very low? If not using sodium bisulphate to lower pH what is the preferred addition?

The sulfates build up in the water over time and have no effect on pH. The hydrogen part of the HSO4- is what affects pH and that will vary over time with the addition of alkaline fill water and alkaline substances. The sulfate (SO4(2-))part of the salt has no impact on pH, it just builds up. The preferred and recommended method of pH reduction is to use muriatic acid (HCl). Chloride ions don’t cause nearly as many corrosion issues as sulfates do.

 

[MarkHoop]

The sulfates build up in the water over time and have no effect on pH. The hydrogen part of the HSO4- is what affects pH and that will vary over time with the addition of alkaline fill water and alkaline substances. The sulfate (SO4(2-))part of the salt has no impact on pH, it just builds up. The preferred and recommended method of pH reduction is to use muriatic acid (HCl). Chloride ions don’t cause nearly as many corrosion issues as sulfates do.

Hmmm, ok so if this is the problem then is it likely that high sulphates would go unrecognized in a "balanced" pool? If no, what typical attribute would have been off?
Is there a way to determine definitely if the sulphates are in fact higher than would be ideal?

 

[JoyfulNoise]

Hmmm, ok so if this is the problem then is it likely that high sulphates would go unrecognized in a "balanced" pool? If no, what typical attribute would have been off?
Is there a way to determine definitely if the sulphates are in fact higher than would be ideal?

Sulfates don’t affect the balance of any pool chemistry level that you would measure nor is there a simple way to test for them. When sulfates get high enough, they can cause scaling similar to calcium carbonate scaling except for the fact that calcium sulfate doesn’t react strongly with acids. So scale that is a mixture of calcium carbonate and calcium sulfate will bubble and fizz when acid is applied to it but then you’ll see the calcium sulfate left behind as a solid residue that only very very slowly dissolves.

There is no simple test for sulfates. Only a water testing lab with the correct test equipment can determine sulfate levels accurately. Anything over 200 to 300ppm is worrisome as that is when you can see deleterious effects of sulfate exposure (corrosion, scale, concrete attack, etc).

 

[1poolman1]

I don't think a bond wire was a requirement when the pool was installed over 20 years ago. As far as chemicals go just the typical ones for alkalinity and hardness. All in closed containers

Electrical bonding of a pool has been a requirement for over 35 years. Probably more than that. My pool, built in the 1980s is bonded.

 

[JamesW]

The NEC required pools to be bonded beginning in 1962. They increased the required wire size in 1965 and added the 5ft rule in 1968, so your pool built in 1970 should be bonded.

 

[JamesW]

“Swimming pools first appeared in the NEC in the 1962 edition, and the section was a brief three pages long.

Here’s the first bonding citation in the 1962 code, although it was not initially called bonding:

680-7. Grounding

- (a) All metallic conduit, piping systems, pool reinforcing steel, light fixtures, and the like, shall be bonded together and grounded to a common ground.

The metal parts of ladders, diving boards, and their support, shall be grounded.

- (b) No pool equipment shall be grounded to an external grounding electrode that is not common to the pool ground (deck box or transformer enclosure).

- (c) An unbroken No. 14 AWG, or larger, insulated copper wire shall be provided for a grounding conductor from the deck box to the distribution panel ground.

- (d) Metallic raceways shall not be depended upon for grounding.

Where exposed to pool water and in other corrosive areas such as in pump houses or adjacent to water treating and other equipment, the grounding of the non-current carrying parts shall be by means of an insulated copper conductor sized in accordance with Section 250-95.

The 1965 edition changed the ground wire requirement from #14 AWG to the larger #8 AWG, along with other minor additions.

Then the 1968 edition introduced the word “bonding” for the unbroken connection between all components that was required, and specified the five-foot radius rule that we know today.

Equipotential bonding code has continued to be improved in each code cycle up to today.

While the year that the NEC added a new requirement is easy to define, each local jurisdiction’s building codes don’t necessarily adopt the latest edition of the NEC immediately.

The state of Florida, for example, did not make the 2011 NEC effective until mid-2015.

Other jurisdictions have sometimes waited even longer to adopt a newer NEC edition and, to complicate things further; they might make amendments that exclude parts of the newest requirements.

So the year when the NEC first adds or changes a requirement can be several years before your local building department adopted that edition of the code and began enforcing it”.

When was pool bonding first required by code?

www.howtolookatahouse.com

 

[JamesW]

Article 680 first appeared in the 1962 edition of the NEC.

Note that the OP is in Canada and they will have a different time when pool bonding was first introduced.

Also, jurisdictions do not automatically adopt the current NEC as law.

So, there can be a delay of several years from a code change to it becoming law in your area.

NEC Article 680 — Diving Into 2023 NEC Proposed Changes

iaeimagazine.org