# Thread: SWG % - What is it a percentage of and other questions

1. ## SWG % - What is it a percentage of and other questions

I have the Hayward T15 cell with the pro logic 8 controller. I understand that to set your chlorine levels you set the SWG % until you get the FC levels that you want.

My question is, when you set the SWG to 50%, what is that 50% of? Total of all programmed run times? How does it run during its 50% run time? Let's say I have a program time of 8 hours, does it run for the first 4 hours and stop? Does it run for 10 minutes on and then 10 minutes off until it hits 4 hours, or something else?

How does it know when 50% is hit when I manually turn on the pump and run it? It has no idea when I am going to turn it off, but the SWG is running, so when does it shut itself off, if ever, in that situation?

Just trying to understand how the cell is running so I can be better informed when making adjustments to both the pump run times and % settings.

2. ## Re: SWG % - What is it a percentage of and other questions

The SWG turns on for the given percentage of the time the pump is running. Typically they figure out the on/off times for each one hour period, ie 50% is 30 minutes on and 30 minutes off, but that varies a bit by brand. A few SWGs actually modulate their activity level, and are "on" the whole time, but that is rare.

3. ## Re: SWG % - What is it a percentage of and other questions

Here is how the Hayward cells work (per our trainer who worked at Hayward for 8 years until recently). They run in three-hour cycles before reversing the polarity to help keep the plates clean. Within that 3-hour window, the % of runtime is applicable. When the next 3-hour window comes up, it starts over. So if you have it set for 50%, then change it to 5% (and are all within a 3-hour cycle window) it will say % of runtime has been exceeded or something similar (assuming it had run for more than the 9 minutes the 5% would calculate out to) . But once it gets to the next 3-hour window, the 5% will be in effect.

4. ## Re: SWG % - What is it a percentage of and other questions

Thanks for the info.

So if I understand bmoreswim right:

If I turn on my filter manually for 4 hours and my SWG is set to 50%, it will run for the first 1.5 hours (50% of the first 3 hour cycle) and then turn off for the next 1.5 hours. Then it will run for an hour until I turn off the filter (after a total 4 hour run time). In other words, it always assumes a minimum run time of 3 hours and adjusts its percentage to that and recalculates every 3 hours.

5. ## Re: SWG % - What is it a percentage of and other questions

Yes, however it could also run for 30 minutes at a time and cycle that during the three-hour period so that it runs for 50% of that three hours. I'm not sure what the cycle is in that respect. And it may vary depending on what the percentage is. You can tell when you're saltwater cell is running by looking for bubbles coming out of the returns. I just figured that out today. The chlorine being formed is in a gas state.

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