Check my assumptions on SWG understanding

[foobert]

Do I understand correctly that the output percent adjustment changes the amount of time that the cell is actually powered, ala, pulse-width modulation at the respective percentage of on-time? Thus, if electric costs are ignored, would there be any difference to cell life between running for 4 hours per day at 100% vs 8 hours at 50%?

I see that the Autopilot systems have a 3-step current adjustment. If the daily chlorine output were equalized between the 3 current settings (i.e. low current-->more hours, high-current-->fewer hours on), does one mode lead to longer cell life than another?

And finally, how does a properly cleaned and cared for cell go bad at the end of it's life? Does the generated chlorine output slowly decline to the point that 24 hours of run time no longer produces the necessary CL2? Or is it typically a binary failure mode -- worked yesterday and now it doesn't?

For reference, I'm looking at the Auquarite w/ -15 cell, vs a Nano/Digital w/ -42(-48?) cell. I've already read many of PoolSeans pitches on the merits of the autopilot system, so I'm not looking to turn this into another one of those threads.

 

[JoyfulNoise]

Do I understand correctly that the output percent adjustment changes the amount of time that the cell is actually powered, ala, pulse-width modulation at the respective percentage of on-time? Thus, if electric costs are ignored, would there be any difference to cell life between running for 4 hours per day at 100% vs 8 hours at 50%?

Yes, it's a "duty cycle" method of powering the cell so 8hrs/50% is equivalent to 4hrs/100%.

I see that the Autopilot systems have a 3-step current adjustment. If the daily chlorine output were equalized between the 3 current settings (i.e. low current-->more hours, high-current-->fewer hours on), does one mode lead to longer cell life than another?

I have a Pentair IntelliChlor which is a constant voltage power supply. So not sure how the other systems work.

And finally, how does a properly cleaned and cared for cell go bad at the end of it's life? Does the generated chlorine output slowly decline to the point that 24 hours of run time no longer produces the necessary CL2? Or is it typically a binary failure mode -- worked yesterday and now it doesn't?

The plates are titanium (in good quality cells) coated with a transition metal oxide (ruthenium, rhodium, platinum) catalyst layer. The catalyst layer wears down after a while and exposes the titanium. The titanium will anodize in water and effectively become non-conductive. The reduced surface area shows up as a "low salt" alarm and FC production diminishes. Eventually the power supply will clamp at high voltage or current and the whole system just starts to produce less chlorine.

 

[Jimrahbe]

Foobert,

Just curious.. if you already have an "automated chlorine system", which is in your signature, why do you want to install a SWG? Keep in mind that in the winter, the SWG will shut off, and you will have to add chlorine/bleach anyway.

Jim R.

 

[foobert]

Mostly, I'm tired of lugging jugs of bleach around. Lessor issue was that it always required more fidgeting than I was happy with to keep it maintained (plumbing issues, predominately).

Edit: Also, I can re-purpose the system to do acid injection w/ the SWG, so, it won't go to waste. It will be much happier not pushing quarts of fluid per day through it

 

[Vickery]

As far as "PWM" is considered, on many units the "pulse" is for the duration that the internal timer switches it on, rather than a pulse width that would correspond to a frequency greater than 1 hz. But running time accumulates the same either way.

 

[foobert]

The plates are titanium (in good quality cells) coated with a transition metal oxide (ruthenium, rhodium, platinum) catalyst layer. The catalyst layer wears down after a while and exposes the titanium. The titanium will anodize in water and effectively become non-conductive. The reduced surface area shows up as a "low salt" alarm and FC production diminishes. Eventually the power supply will clamp at high voltage or current and the whole system just starts to produce less chlorine.

OK. So, over time, I should expect to see a gradual increase in run-time as the cell ages. I'm on time-of-use electric metering with an 8 hour window of "cheep" power to get the bulk of pump run-time completed. W/ a 1.4lb/day cell, 8 hours yields 2.2ppm increase in FC at 100% duty cycle -- just about right, but, no headroom for production decline.

 

[bobandsherry]

Foobert,

Just curious.. if you already have an "automated chlorine system", which is in your signature, why do you want to install a SWG? Keep in mind that in the winter, the SWG will shut off, and you will have to add chlorine/bleach anyway.

Jim R.

I'm a noob to the SWG, just had inground pool installed and had SWG added. I saw your comment regarding the SWG shut off in winter. I expect that in my area the water won't get below 60 in Dec-Feb which is within the range for my SWG. PB didn't mention anything about winter months, is there something that I need to be concerned with?

 

[Jimrahbe]

Bob,

I'm not sure about your particular SWG, but on mine (Pentair IC40) a light actually comes on saying the unit is shut off due to cold water. I think in theory it shuts off at 52 degrees, but in reality it seems it is closer to 55 to 57 degrees.

I believe that most SWGs operate in a similar fashion. Not really an issue, as you don't need much chlorine when the water is that cold anyway, but something to keep in mind.

Jim R.

 

[JoyfulNoise]

OK. So, over time, I should expect to see a gradual increase in run-time as the cell ages. I'm on time-of-use electric metering with an 8 hour window of "cheep" power to get the bulk of pump run-time completed. W/ a 1.4lb/day cell, 8 hours yields 2.2ppm increase in FC at 100% duty cycle -- just about right, but, no headroom for production decline.

Can you afford a larger, 2lbs cell (IC60 or AutoPilot RC52)? I think there's even a 3lb cell available.

 

[needsajet]

Larger cell would be nice and life-cycle cost improves with a larger cell, so if it were mine, I'd go with a different brand to get a larger cell and sort out the control aspects.

That said, the VS pump is beneficial because you might be able to dial down the speed and increase run time to give you some FC production headroom when needed. I guess that might extend past the overnight electricity rates, but at least provides an option.

 

[foobert]

I'm going to go ahead and step up to the 2lb/day cell. That rules out the more economical Aquarite system, but, I suspect the Autopilot will be a less fiddly system anyway. Placing the order tomorrow.