SWG run time calculations assistance

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Thanks for the assistance. I already know my losses. I need to know how long to run the SWG to generate 2 ppm. By the advertised specifications it should be around 2.5 hours. After 3 hours I still wasn't seeing +2, which is what prompted this thread.
 
sbcpool said:
OCLT begins. Took two samples from different places and different depths. Sample from surface at skimmer read 5.8 and one from about 12 inches deep in the deep end read 6.0.
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How are you testing? Those numbers don't seem to be from a TFP recommended testing method.
 
I fired up the pump and set the control unit to 5%. It began producing shortly. If the cell is on a 3-hour cycle I expect it would shut off after 9 minutes and remain off for the next 171 minutes. It shut off after 8.5 minutes. I will investigate 10% and 20% settings to see if they're at 17 minutes and 34 minutes, indicating a 170-minute cycle, or if it's just a rounding error for a 3-hour cycle.
 
Merged threads. TFP Mod
My situation:
  • CircuPool RJ60+
  • 20,000 gallon pool
  • pH: 7.5
  • Salt: 3900 (according to strips and the CircuPool)
  • Pump run time: 4 hours
  • SWG setting: 100%
  • CYA ~50 ppm
By my calculations and verified by the Pool Math App, 4 hours of 100% SWG run time should generate 3 ppm FC in my pool. However, I have repeatedly measured only 1 ppm increase between night time and morning FC tests over the past two weeks. I performed an OCLT and lost only 0.2 ppm. When you factor in a 0.2 ppm overnight loss, my real net FC generation is only 0.8 ppm.

I ran the pump for 11 hours the night before last, and still yesterday evening I was at 4.5 ppm. I should have been somewhere around 9 ppm after losing 25% during the day. Both the 4-hour runtimes and 11 hours are consistent with an actual output of only 0.2 ppm per hour, or 0.8 lbs. per day.

The SWG is clearly generating as evidenced by the bubbles from the returns and visible verification in the cell itself. The SWG control unit never displays any indication of trouble, showing only the "Power" and "Generating" lights.

I ran through the troubleshooting section of the CircuPool manual. The only thing I can't do at the moment is check nitrates, but I don't experience unexpected FC consumption using liquid chlorine (and phosphates or nitrates consuming FC would show up on an OCLT).

I'll try cleaning the cell even though it's brand new, but after that I'm out of options. Hoping someone here might have an idea before I bug CircuPool.
 
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I see where you passed the OCLT back on 23 July, but it doesn't look like you ever increased the CYA. Any reason why not? For my RJ-45, I was seeing an FC loss per day in the hot summer unless I had at least a CYA of 70. Since then, I've had to reduce my output% twice.
 
Just got off the phone with CircuPool, who told me, "As long as there's free chlorine in the pool I don't see the problem. I don't know what you're trying to accomplish with these 'experiments' you're running."

I'm just trying to avoid changing too many variables at once. My pool has been running 40 - 50 CYA for 5+ years, so I'm very used to chlorine demand at those levels. I know when I have 6 ppm at the start of the day I should have about 4 - 4.5 ppm at the end of the day. All of this frustration has been that I have to run the pump 11 hours with the SWG at 100% to get back up to 6 ppm from 4 ppm, when the advertised capability of the cell should require only 3 hours. Now CircuPool is telling me that as long as there's ANY free chlorine at all, they consider the unit to be working as expected.
 

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sbcpool said:
My pool has been running 40 - 50 CYA for 5+ years, so I'm very used to chlorine demand at those levels. I know when I have 6 ppm at the start of the day I should have about 4 - 4.5 ppm at the end of the day.
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Same here. I was liquid chlorine with a CYA of 50-60 for the past 7 years. But we know the SWG is cycling those smaller amounts of gas throughout the day. Without a higher CYA, your FC simply won't hold as well. We know TFP recommends 70-80, and I believe Circupool was one of the first to finally recommend a higher CYA as well (70 I think in the manual)? Once I got that CYA back up, my FC stabilized and matches my anticipated FC output per day for my unit. When I check my FC each evening, it's just about right where I expect it to be.
 
Texas Splash said:
Same here. I was liquid chlorine with a CYA of 50-60 for the past 7 years. But we know the SWG is cycling those smaller amounts of gas throughout the day. Without a higher CYA, your FC simply won't hold as well.
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My SWG doesn't run throughout the day. My pump only runs from 10 pm to 2 am. That's it. An SWG that generates 3.1 lbs per day should generate about 0.125 lbs every hour, or ~0.5 lbs after four hours. 0.5 lbs is the equivalent of a 1/2-gallon of 12.5% liquid chlorine, which has been my usual routine for years. Am I going wrong in assuming that running an SWG long enough to generate 0.5 lbs FC should have the same effect as manually adding 0.5 lbs FC?

Texas Splash said:
We know TFP recommends 70-80, and I believe Circupool was one of the first to finally recommend a higher CYA as well (70 I think in the manual)? Once I got that CYA back up, my FC stabilized and matches my anticipated FC output per day for my unit. When I check my FC each evening, it's just about right where I expect it to be.
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Does your RJ45+ generate 0.5 ppm every hour at 100% (or 0.25 ppm per hour at 50%) as it should in your pool according to its rated capacity?
 
I've actually never tried to break-down FC production by the cycle. I think I would just drive myself nuts. I found it best to just keep it simple. For example, if I expect my unit to produce 4 ppm of FC in 24 hrs based on my output% and pump runtime, then tomorrow my FC should be at "X" amount when I test (or close to it). Even though some SWG owners program their output at a higher % and less runtime, it's not the same as liquid chlorine. So if someone decided to run at 100% for a very short, one-time FC production expecting it all to last 24 hrs, it may not. Not sure if that's a chlorine gas versus liquid compound thing or what. Some of our TFP chem-geeks know that better than me. :)
 
I see. The unit might generate 3.1 lbs of chlorine gas per day, but that's not necessarily going to end up in your pool. It's sort of like how some LED light bulb manufacturers specify the lumen rating of the emitter itself as the bulb's brightness even though the actual lumens leaving the bulb will be significantly less after accounting for internal reflection, absorption, and other losses.

Well, shoot. That puts a huge cramp in my plans. My electricity rates are scheduled to boost by over 25% this fall, so I'm not keen on boosting pump run time by 300%.
 
I think your logic is correct. According to poolmath, running an RJ-60+ for 4 hours at 100% on a 20,000 gallon pool should increase FC by 3.1ppm. I could see it being off by a little. Maybe 3.0 or maybe even 2.5, but getting 1/3 of the expected output definitely seems like something is wrong.

Are you certain that it’s actually running constantly for those 4 hours. I wonder if it’s detecting low flow and not generating for part of the time, or if it’s detecting a high or low salt level, which would stop generation. How is it wired? If it’s connected to a timer is it possible that the timer is misconfigured or faulty? I’m wondering if somehow it’s actually just running for 1 hour and not 4 hours.

The other thing you can check is to make sure you have the right cell type selected. Keep hitting menu until you get to cell type and make sure it is set to RJ+60.

The only other possible thing I can think of would be the voltage. The SWG can run on 120V or 240V, but it comes factory set for 240V and you need to open it up and move some jumpers if you want to run it at 120V. Is it possible that it is set for 240V, but you are actually running it at 120V? Frankly I don’t know what it would do in that situation - It might not even power up at all. But I’m trying to think of anything that might be out of the ordinary that could cause it to produce such a low amount of chlorine.
 
Brett S said:
I think your logic is correct. According to poolmath, running an RJ-60+ for 4 hours at 100% on a 20,000 gallon pool should increase FC by 3.1ppm. I could see it being off by a little. Maybe 3.0 or maybe even 2.5, but getting 1/3 of the expected output definitely seems like something is wrong.

Are you certain that it’s actually running constantly for those 4 hours. I wonder if it’s detecting low flow and not generating for part of the time, or if it’s detecting a high or low salt level, which would stop generation. How is it wired? If it’s connected to a timer is it possible that the timer is misconfigured or faulty? I’m wondering if somehow it’s actually just running for 1 hour and not 4 hours.
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Now that you mention it, I have walked out at night about 45 minutes after start time and seen the cell not producing anything and the unit still shows POWER and GENERATE as the only lights. I just figured it was a normal cycling of the cell (even at 100%). It honestly didn't occur to me to wait around and see how long it took to come back on (or if it did at all).
 
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sbcpool said:
Now that you mention it, I have walked out at night about 45 minutes after start time and seen the cell not producing anything and the unit still shows POWER and GENERATE as the only lights. I just figured it was a normal cycling of the cell (even at 100%). It honestly didn't occur to me to wait around and see how long it took to come back on (or if it did at all).
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Yeah, something definitely sounds wrong there. A) When it’s set to 100% it will generate 100% of the time for however long you run it. There is no cycling at 100%. And B) Even when it’s set to less than 100% and it does cycle, the GENERATE light will turn off when it’s in the off portion of the cycle. If the GENERATE light is on and you aren’t seeing the cell producing anything then something is definitely not right.
 
Holy moly! If I keep running my single speed pump, moving to 12 hours run time every night increases my power bill by $793 per year at my current rates. Just the power increase alone is more than I spend on liquid chlorine. Moving to an Intelliflo at a low setting with a 12 hour run time will save $169 per year, or about 8 year payback.
 
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OK. Test completed. I checked on the unit every 10-20 minutes for the whole 4 hours. It was generating every time I looked. I may have been thinking of when I first started up the SWG and it was at 50%.

FC this AM was 5.5 and after 4 hours at 100% it's 6.5. The ~0.2 ppm FC per hour has been reliably repeatable across run times, times of day, sample location, and sample depth. It appears that's just what this unit is capable of producing in terms of actual free chlorine in the water. If this is all accurate, the RJ60+ in my system has a real-world FC-generating capability of 0.8 lbs per day. I wish I had known that SWG ratings were not net FC in the pool, but in hindsight it should have been obvious. Most products are marketed in the most positive way possible.

If someone wants to make their own RJ+ output calculator in Excel, here's the raw setup:
Pool Size (gallons):
Pump Run Time (hours):
SWG Power (%):
SWG Rating (lbs per day):
FC Output per day:=ROUND((((INT(B2/3)*(3*B3))+MIN(MOD(B2,3),(3*B3)))*((B4*453592)/24))/(B1*3.78541178),2)

It should paste right into Excel.

This assumes that the RJ+ series operates on a ON/OFF 3-hour cycle. 50% for 3 hours means 90 minutes on, 90 minutes off. 50% for 4 hours means 90 minutes on, 90 minutes off, 60 minutes on.
 
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