- Mar 5, 2020
- 3,221
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
I seem to have a problem with the new SWG that I bought a few months ago. Wanted to keep it out of the public forums for now until I settled potential warranty claims. Maybe a topic for @JoyfulNoise and @JamesW. Or @AUSpool and @aussieta with the local knowledge.
My old Hurlcon VX7T SWG (7-plate cell, 25 g/h (Cl₂), main unit from 2005, cell from 2007, Hurlcon is now AstralPool Australia) started behaving badly, so I had ordered a new one before it failed completely with lead times so long back then. I replaced it with an AstralPool Viron V35 (11-plate cell, 35 g/h (Cl₂)).
New SWG was finally installed at the end of last summer when temperatures were starting to get colder. But Aussie SWGs usually run all through winter. After a while I noticed that I had to crank up the SWG more than expected to keep FC constant. CYA at the time was still 80ppm, salt around 5000 ppm, temperature around 15°C. Did OCLT to rule out algae, all good. Fluidra customer service said that below 15°C the unit halves the Cl₂ output. So I let it be.
Once the temperature was back above 15°C recently, I started testing again. CYA at 60ppm (had torrential rains here, only add enough CYA to keep it above 60ppm right now, still spring here, otherwise I'm simply washing more down the drain - La Niña year). Salt around 5000ppm (most Aussie SWGs are designed to run at higher salt levels). And it still looked like the Cl₂ production is too low.
So I made another OCLT, still all good there. Then I did a proper "OCGT" (overnight chlorine gain test). My pool has 66000 liters, so a 35 g/h should produce about 0.53ppm FC/h at 100%. Running it for 9.5 hours over night, should add about 5ppm. Temperature around 19°C at the time. It added 2.5ppm.
Then I went into measuring the current. I should mention that my SWG (like many Aussie models) doesn't work on a duty cycle, it adjusts the current to regulate the Cl₂ production. You set it to a setting between 1 and 8, with 8 being 100%. It then shows you the setting it actually achieved, but not the actual current. If you set it for example to 8, it should also show 8 as the resulting "current". If it shows less, it produces less than it should, e.g. due to low salt. My Viron always showed the intended current value (The old Hurlcon couldn't get up to 8 anymore, which is why I replaced it).
Anyway, I got out my multimeter and hooked it up, measuring the current from 0 to 8. I also calculated the chlorine output per current. I summarised the results in this slide, also with a picture of the gas production at 100% as visible through the clear cell housing:
Summary: The measured cell current of 5.5A (corrected by the zero-current) is slightly more than in theory required to produce 35 g/h. So the unit obviously "thinks" it produces enough chlorine. But it doesn't.
To be sure that salt wasn't too low, I then added two more bags of salt, and did the same test with the same result. That got my salt up to about 5800ppm (the AstralPools are specified up to 8000ppm, and with our torrential rains at the moment this should come down quickly). At the time I thought my salt was a bit lower based on my salt meter reading, but in the meantime my fresh Taylor supplies arrived from the US and the 5800ppm is as measured with the Taylor salt test.
Then I hooked up my old Hurlcon SWG, which (apart from not reaching level 8 in it's older days) always seemed to produce chlorine as specified, and went through the same exercise:
As expected, The Hurlcon didn't increase the current beyond setting 7, but extrapolating the linear curve to 8 shows that the unit would have been aiming for 6.5A at setting 8, which would in theory result in slightly more than the specified 25 g/h.
Then I ran an OCGT with the Hurlcon, but only on setting 7. This should result in as Cl₂ production of about 21.9 g/h, which is FC 0.33 ppm/h in my pool. Running the same 9.5h over night, this should increase FC by about 3.1ppm. The result was again an FC increase over night of about 2.5ppm.
Summary:
The Hurlcon pretty much produces the expected amount of chlorine, but the new Viron V35 is basically 50% too low. Hurlcon basically produces on setting 7 with its 25g/h cell the same amount of chlorine as the Viron on setting 8 with its 35g/h cell.
But the current measured with the Viron, matches the specification, so it certainly thinks it is producing enough. Also, when you compare the photos with the gas clouds in the cells, the Viron seems to produce more gas than the Hurlcon. But I suspect that there is more than just H₂ and Cl₂ in that gas cloud.
Looking into the chemistry of NaCl (aq) electrolysis, there are two competing reactions possible at the anode (from chem.libretexts.org):
(i) 2Cl+(aq)⟶Cl₂(g)+2e-, E⁰=+1.35827V
(ii) 2H₂O(l)⟶O₂(g)+4H+(aq)+4e-, E⁰=+1.229V
Based on potentials, reaction (ii) is preferred, but due to overpotentials, reaction (i) is actually what should predominantly happen in an SWG cell. And I think this is where the Ruthenium coating is very important to catalyze the desired reaction.
So, now I finally come to the question that I actually have: Could there be something wrong with the Ruthenium coating of the cell, and the cell is not just producing Cl₂ at the anode, but also O₂? Under which circumstances would that even be possible? Something must discharge at the anode to create the current I measured, but it obviously is not just Cl- turning into Cl₂. I bought the new chlorinator at a time where I had to wait about 2 months to get it delivered, and it then had a production date that was just a week or so earlier. I suspect that one aspect in that long lead time might have had something to to with the availability of ruthenium in Australia after our monster Covid-19 lock-downs.
(EDIT: Turns out that it was a problem with the cell's plates assembly, see posts #23, #39, #40.)
The only other explanation I came up with with be electrical shorts between some of the cell plates, but I ruled that out by testing the resistance between plates, which was in the MΩ range, which I attribute to the cell still being wet when doing the resistance measurement.
The new cell had never been acid cleaned. I have 50ppm borates in the water, and the plates are as clean as on day 1. TA usually between 70 and 80ppm, CH around 400ppm, pH mostly above 7.8, verified with an Apera PH60 (calibrated at pH 4, 7 and 10.01).
I already talked with the store where I bought the SWG. Generally quite happy with that shop, and I buy all my hardware there. But when I explained to them that my SWG is not producing enough, and that I confirmed that with FAS-DPD testing, they looked at me as if I had walked in full Astronaut gear into the shop. I think I need a bit more substance to make a successful warranty claim.
Sorry for the long post, but I thought I try to cover the full story. Hope the picture is complete enough for a diagnosis. Or to reconfirm my status as a complete nerd with OCD.
EDIT:
Should add that FC was in the whole period where I ran these tests between 8 and 12ppm. I keep it around 10ppm over winter. Before going on holidays in July, I bumped it up to 21ppm, when I came back after 4 weeks it was at 9ppm (at about 10°C), no sign of algae.
My old Hurlcon VX7T SWG (7-plate cell, 25 g/h (Cl₂), main unit from 2005, cell from 2007, Hurlcon is now AstralPool Australia) started behaving badly, so I had ordered a new one before it failed completely with lead times so long back then. I replaced it with an AstralPool Viron V35 (11-plate cell, 35 g/h (Cl₂)).
New SWG was finally installed at the end of last summer when temperatures were starting to get colder. But Aussie SWGs usually run all through winter. After a while I noticed that I had to crank up the SWG more than expected to keep FC constant. CYA at the time was still 80ppm, salt around 5000 ppm, temperature around 15°C. Did OCLT to rule out algae, all good. Fluidra customer service said that below 15°C the unit halves the Cl₂ output. So I let it be.
Once the temperature was back above 15°C recently, I started testing again. CYA at 60ppm (had torrential rains here, only add enough CYA to keep it above 60ppm right now, still spring here, otherwise I'm simply washing more down the drain - La Niña year). Salt around 5000ppm (most Aussie SWGs are designed to run at higher salt levels). And it still looked like the Cl₂ production is too low.
So I made another OCLT, still all good there. Then I did a proper "OCGT" (overnight chlorine gain test). My pool has 66000 liters, so a 35 g/h should produce about 0.53ppm FC/h at 100%. Running it for 9.5 hours over night, should add about 5ppm. Temperature around 19°C at the time. It added 2.5ppm.
Then I went into measuring the current. I should mention that my SWG (like many Aussie models) doesn't work on a duty cycle, it adjusts the current to regulate the Cl₂ production. You set it to a setting between 1 and 8, with 8 being 100%. It then shows you the setting it actually achieved, but not the actual current. If you set it for example to 8, it should also show 8 as the resulting "current". If it shows less, it produces less than it should, e.g. due to low salt. My Viron always showed the intended current value (The old Hurlcon couldn't get up to 8 anymore, which is why I replaced it).
Anyway, I got out my multimeter and hooked it up, measuring the current from 0 to 8. I also calculated the chlorine output per current. I summarised the results in this slide, also with a picture of the gas production at 100% as visible through the clear cell housing:
Summary: The measured cell current of 5.5A (corrected by the zero-current) is slightly more than in theory required to produce 35 g/h. So the unit obviously "thinks" it produces enough chlorine. But it doesn't.
To be sure that salt wasn't too low, I then added two more bags of salt, and did the same test with the same result. That got my salt up to about 5800ppm (the AstralPools are specified up to 8000ppm, and with our torrential rains at the moment this should come down quickly). At the time I thought my salt was a bit lower based on my salt meter reading, but in the meantime my fresh Taylor supplies arrived from the US and the 5800ppm is as measured with the Taylor salt test.
Then I hooked up my old Hurlcon SWG, which (apart from not reaching level 8 in it's older days) always seemed to produce chlorine as specified, and went through the same exercise:
As expected, The Hurlcon didn't increase the current beyond setting 7, but extrapolating the linear curve to 8 shows that the unit would have been aiming for 6.5A at setting 8, which would in theory result in slightly more than the specified 25 g/h.
Then I ran an OCGT with the Hurlcon, but only on setting 7. This should result in as Cl₂ production of about 21.9 g/h, which is FC 0.33 ppm/h in my pool. Running the same 9.5h over night, this should increase FC by about 3.1ppm. The result was again an FC increase over night of about 2.5ppm.
Summary:
The Hurlcon pretty much produces the expected amount of chlorine, but the new Viron V35 is basically 50% too low. Hurlcon basically produces on setting 7 with its 25g/h cell the same amount of chlorine as the Viron on setting 8 with its 35g/h cell.
But the current measured with the Viron, matches the specification, so it certainly thinks it is producing enough. Also, when you compare the photos with the gas clouds in the cells, the Viron seems to produce more gas than the Hurlcon. But I suspect that there is more than just H₂ and Cl₂ in that gas cloud.
Looking into the chemistry of NaCl (aq) electrolysis, there are two competing reactions possible at the anode (from chem.libretexts.org):
(i) 2Cl+(aq)⟶Cl₂(g)+2e-, E⁰=+1.35827V
(ii) 2H₂O(l)⟶O₂(g)+4H+(aq)+4e-, E⁰=+1.229V
Based on potentials, reaction (ii) is preferred, but due to overpotentials, reaction (i) is actually what should predominantly happen in an SWG cell. And I think this is where the Ruthenium coating is very important to catalyze the desired reaction.
So, now I finally come to the question that I actually have: Could there be something wrong with the Ruthenium coating of the cell, and the cell is not just producing Cl₂ at the anode, but also O₂? Under which circumstances would that even be possible? Something must discharge at the anode to create the current I measured, but it obviously is not just Cl- turning into Cl₂. I bought the new chlorinator at a time where I had to wait about 2 months to get it delivered, and it then had a production date that was just a week or so earlier. I suspect that one aspect in that long lead time might have had something to to with the availability of ruthenium in Australia after our monster Covid-19 lock-downs.
(EDIT: Turns out that it was a problem with the cell's plates assembly, see posts #23, #39, #40.)
The only other explanation I came up with with be electrical shorts between some of the cell plates, but I ruled that out by testing the resistance between plates, which was in the MΩ range, which I attribute to the cell still being wet when doing the resistance measurement.
The new cell had never been acid cleaned. I have 50ppm borates in the water, and the plates are as clean as on day 1. TA usually between 70 and 80ppm, CH around 400ppm, pH mostly above 7.8, verified with an Apera PH60 (calibrated at pH 4, 7 and 10.01).
I already talked with the store where I bought the SWG. Generally quite happy with that shop, and I buy all my hardware there. But when I explained to them that my SWG is not producing enough, and that I confirmed that with FAS-DPD testing, they looked at me as if I had walked in full Astronaut gear into the shop. I think I need a bit more substance to make a successful warranty claim.
Sorry for the long post, but I thought I try to cover the full story. Hope the picture is complete enough for a diagnosis. Or to reconfirm my status as a complete nerd with OCD.
EDIT:
Should add that FC was in the whole period where I ran these tests between 8 and 12ppm. I keep it around 10ppm over winter. Before going on holidays in July, I bumped it up to 21ppm, when I came back after 4 weeks it was at 9ppm (at about 10°C), no sign of algae.
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