Run time vs percentage of production, SWG

[TulsaKevin]

I have my salt cell running around 75%, but I am noticing that my chlorine levels are slightly lower than I need for my CYA.

I did turn my filter run time down some over the winter, my pool has been clear and had no real chlorine demand.

So, would it be better to increase run time or percentage of output.

My filter is a 2 hp variable speed, of which I could adjust the speed.

 

[mas985]

For energy efficiency, it would be much better to raise the % than increase run-time. But it doesn't matter to the SWG.

 

[JVTrain]

Your pump speed won't change how much chlorination you need or are outputting. It's about economics. You're likely better off increasing your output % rather than increasing your pump run time because it will cost you less. Running at a higher percentage may burn out your SWG cell sooner, but only over the long term life of the cell.

My advice would be increase output as high as you need to up to 100%, then if that's not enough, only then go to longer pump run times (SWG run time). Your cell may be undersized for your pool. With your size pool, next time you get an SWG cell, go as big as you can. Most SWG cell manufacturers go up to 40K rated cells. The guideline here on TFP is to over size your cell based on 2x your actual volume. Look into at least a Pentair IC60 or similar larger sized SWG cell when yours needs replacement.

 

[Texas Splash]

This has got to be one of the most popular questions at TFP. Mark & Joel are well-versed in this area, so you're off & running. But along with the advice already provided, always ensure:
- Your water is clear and algae-free; that's critical for the SWG and so you know nothing out of the ordinary is consuming your FC
- You are maintaining that CYA of 70-80 which is extremely important for a SWG pool to save FC and reduce SWG output (save cell life)

Regardless, always refer to these two pages as well: Pool School - Water Balance for SWGs and Pool School - Determine Pump Run Time

 

[pooldv]

I agree with raising the output percentage as long as it isn't to 100%. I would stop at 80% or so and then start increasing run time. I am not a fan of running anything at 100%.

 

[mas985]

Doesn't seem like it would make any difference if the SWG ran at 100% or 80% (for longer). The actual run time for the SWG is exactly the same. Thermal stability is reached fairly quickly so there would be no more thermal stress or load to the components. If anything turning and off the electronics more often would be more likely to cause transients in the electronics causing a very slight increase failure rates. Also, more thermal cycling is known to reduce MTBF.

I wouldn't worry about running at 100%.

 

[pooldv]

Matt and I have been discussing this recently and think the impact of running a cell at 100% power for long periods of time could be detrimental to the coating on the cell and lead to scaling formations. By contrast, when you run a cell at lower duty cycle (50% ON / 50% OFF, 70/30, etc) for longer time, you potentially reduce the wear and tear on the metal coating and allow the cell to "rest". This also gives a chance for lower CSI water to dissolve any calcium scale that might form. When the cell is producing chlorine, the water environment inside the cell is incredibly harsh (high pH, caustic water, tons of aeration) and so scaling is much more likely than not inside the cell even when the water entering the cell has low CSI.

 

[mas985]

Chlorine production by chemical electrolysis has been around for over a century and mostly in industrial applications. If what you say were true, I am sure someone has written about it in one of the scientific journals because of the cost impacts to chlorine production. Have you seen this written about in any scientific papers?

Also, electrolytic cells are usually rated in amp-hours and as far as I know there are no conditions set on duty cycle. Added to that my own experience of my last cell lasting close to 10 years with much of the time at or near 100%, I really don't see how this can possibly be true.

 

[pooldv]

I agree that if running a cell at 100% were a potential problem it would be written about in the industry. And likely mentioned in my SWG owners manual. It is also likely accounted for in the operation of the cell by the controller.

No, that is all speculation on my part. The only evidence I have is a 4 year old IC40 that is always run at 40%-60% and water that is maintained with negative CSI that has remained spotless and never needed cleaning. This with tap water that causes scale in all plumbing fixtures in the house and the Intex SWG before it needed to be cleaned fairly often because it would develop nearly complete blockage from build up.

So, maybe it doesn't extend cell life but reduces likelihood of build up which reduces the need for cleaning. Or maybe I am just lucky with this cell? I certainly have to acknowledge that a Pentair SWG is vastly superior to an Intex SWG and that alone could account for the improved performance. And most likely of all the Intex pool was not maintained with TFPC and this pool is!

 

[mas985]

A TFPC run pool is the most likely explanation! That's what I account for my cell's long life.

 

[chiefwej]

Running a SWG at 100% is not a problem. In fact, regardless of the percent setting, they always run at 100%. The control setting just cycles power to the cell on and off over a long period of time. The number of hours in a cycle varies depending on make and model SWG, but when it's running it's always at 100%.