Questions about SWG %/runtime ratio

AZAA

Silver Supporter
Apr 9, 2020
82
Gold Canyon AZ
Pool Size
5850
I've been doing some reading of old posts regarding SWG output.
I've discovered that pump speed doesn't affect output. OK, that leaves SWG % and run time.
Pool Math tells me that my "24 hour SWG chlorine output" is .98 but what does that mean? The dropdown menu allows me to select the T-15 cell but nowhere can I find a place to record my runtime. My current runtime (8 hrs) and 10% SWG setting seems to be generating enough chlorine but I would like to know what's actually going on rather than just accepting my dumb luck. I think I'm running my pump at a higher RPM than I need. I was trying to eliminate SWG bubbles, but I've read that they are just a fact of life and won't hurt anything. (Again, I know that pump speed doesn't affect chlorine output, but since I've got you here...)
So... what does .98 chlorine output mean and which of the 2 variables should I adjust to get an acceptable target number?
(And just for the fun of it, let's pretend I don't know squat about all the abbreviations I know you're going to use :unsure: )
 
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Newdude

Gold Supporter
TFP Guide
Jun 16, 2019
6,928
NY
My current runtime (8 hrs) and 10% SWG setting seems to be generating enough chlorine but I would like to know what's actually going on rather than just accepting my dumb luck
SWGs are either on or off. 10% means it is producing 10% of the time it is running and off 90% of that time.

if pool math is saying ‘.98’ or whatevs it means you would be producing that many grams of Chlorine gas. I, myself, never liked the metric math part of this process and always just went back to adjusting runtime % if i needed more or less.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
37,112
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
A Hayward T15 SWCG outputs 1.47 lbs of chlorine gas per 24 hour period at 100% setting. How did you get .98?

In Poolmath, you can use Effects of Adding Chemicals for how much FC your settings will generate each day. Or, you can select FC from the Overview page and select SWG from the drop down list and use that method to show how much FC you are adding.

IF you have a T15, a 10% setting for 8 hours is adding 1ppm FC per day. That is pretty low for right now but I do not know your micro climate. In my pool, I am up to about 2.5 ppm FC per day but my CYA is a bit low so that is most likely why.

For pump speeds, first determine the minimum RPM you need to close the flow switch on the SWCG. Once you have that, see if that skims your pool surface. If so, that is your RPM to use. If you would like more skim action, raise the RPM for at least part of the day.
 

DanF

Silver Supporter
Mar 17, 2019
354
Chandler, AZ
SWGs are either on or off. 10% means it is producing 10% of the time it is running and off 90% of that time.
Kind of. It depends upon the length of the duty, or generation, cycle. I believe the T-15's is the same as my CircuPool RJ-45...180 minutes.

This means that the SWG will be generating chlorine gas for % X 180 minutes, than stop until 180 minutes is reached, then start again.

For example at 40% for 4 hours (240 minutes), the SWG will produce 72 minutes of chlorine, then the generation will stop for 108 minutes, then produce another 60 minutes. This totals 132 minutes of chlorine, or 132/240 = 55%.

Only when you run the SWG in multiples of the duty cycle (3/6/9 hours) do you get exactly the set percentage.
 
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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
37,112
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Only when you run the SWG in multiples of the duty cycle (3/6/9 hours) do you get exactly the set percentage.
Very true --- the Pentair Intellichlor cycle is 5 minutes.
 
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DanF

Silver Supporter
Mar 17, 2019
354
Chandler, AZ
I was trying to eliminate SWG bubbles, but I've read that they are just a fact of life and won't hurt anything.
I was wondering the same thing. When my SWG runs during my pump's low speed, I see bubbles coming from the returns. Later in the day, when the pump is running at high speed, I do not see bubbles. Is this normal and OK?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
37,112
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I was wondering the same thing. When my SWG runs during my pump's low speed, I see bubbles coming from the returns. Later in the day, when the pump is running at high speed, I do not see bubbles. Is this normal and OK?
Yes. The SWCG creates chlorine and hydrogen gas. The chlorine gas readily goes into the water. The hydrogen gas does not and results in bubbles in the return. At low flow rates, you see them. At high flow rates, they are dispersed quickly.
 
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AZAA

Silver Supporter
Apr 9, 2020
82
Gold Canyon AZ
Pool Size
5850
Thank you all for the formula explanations.
I had thought the % setting referred to the performance efficiency of the SWG, not the % of run time.
And Marty, I didn't know that that page even existed in Pool Math. My .98 changed to 1.47 after I found my T15 from the drop down. The resulting 1ppm of FC seems low but the chlorine level has been fairly stable, at least for now. I think I will adjust % if necessary, I like my runtime the way it is.
I haven't found my lowest pump speed yet. That new TriStar VS900 is so darn quiet it barely seems to be running at all!
 

Oly

Gold Supporter
Jun 28, 2017
1,861
Fresno, CA
Pool Size
27000
We are in the rapid upswing phase of daily FC loss now so keep a close eye on your numbers. Best to build in some cushion to stay well ahead of demand to avoid getting behind and avoid all the extra work that requires.
 
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ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
24,903
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Kind of. It depends upon the length of the duty, or generation, cycle. I believe the T-15's is the same as my CircuPool RJ-45...180 minutes.

This means that the SWG will be generating chlorine gas for % X 180 minutes, than stop until 180 minutes is reached, then start again.

For example at 40% for 4 hours (240 minutes), the SWG will produce 72 minutes of chlorine, then the generation will stop for 108 minutes, then produce another 60 minutes. This totals 132 minutes of chlorine, or 132/240 = 55%.

Only when you run the SWG in multiples of the duty cycle (3/6/9 hours) do you get exactly the set percentage.

 

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