SWG run time calculations assistance

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Can't find your pump's head curve to determine the operating point but given you have a heater and filter and not very large pipe, I would not think the flow rate in that system is more than about 80-90 GPM if that. 10 PSI would indicate much lower flow rates. I don't know what the dissolution rate is for chlorine gas but I do know is that your setup is not that exceptional and if this were an issue for your type of pool (i.e. normal except for maybe the returns), I think we would have heard about it by now.

I would try a test in the spa just to see if you get any different results.
 
If you do attempt the spa only test, do not run the air blower. Creating lots of aeration with the chlorinated water will likely just create confusing results, especially with pH.
 
The spa is only 550 gallons. If the Cl2 fully dissolved it would raise FC 28 ppm per hour, or almost 1 every 2 minutes! :eek: If it behaves similarly to the pool it will be about 10 ppm per hour.

Wouldn't directing all return flow to the spa make it even worse, since now there's 50 less feet of return pipe to travel through?

EDIT - I think this is the pump: Aqua-Flo AC-Series Bronze Pump - AquaFlo Bronze Pumps
 
sbcpool said:
Wouldn't directing all return flow to the spa make it even worse, since now there's 50 less feet of return pipe to travel through?
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Yes which is why a spa test is useful. Either it will get worse, if it is related to distance, or it will be about the same, which means it isn't about distance.
 
JoyfulNoise said:
I won't belabor this thread with a lot of math, but 6.45A on a bipolar cell design with 13 plates will yield, on average, ~3 lbs of chlorine gas per 24 hours. So I believe the cell is operating correctly.
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The T-15 Hayward cell has 13 plates and the amperage is about the same for me (6-7 amps). The T-15 cell produces 1.45 lbs/day which is about what the OP is measuring. But does the number of plates really matter. Isn't production proportional just to the amperage? To get 3 lbs/day, the amperage would have to be about 13 amps.

Perhaps the voltage is too low. Is the cell type set correctly in the controller?
 
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Just finished running for precisely 20 minutes in the spa.

START
pH: 7.79
FC: 9.0 (using 10 mL)

END
pH: 7.98
FC: 12.0 (using 10 mL)

The cell type is set to RJ+60 in the controller. The manual does say the current should be 6 - 8 Amps.
 
What's interesting is that the manufacturer makes no distinction between models when describing the amperage. Maybe my understanding of electrolysis is wrong, but it seems like you can't have one electrode produce 4 times as much byproduct with the same number of electrons as another electrode. The RJ16+ is rated for only 0.7 lbs/day and the RJ60+ is rated for 3.1 lbs/day - 443% more. From my understanding it's impossible that they both consume the same number of electrons per unit of time.

EDIT - They do specify 2.5 - 8.0 amps (page 9), which comes close to covering the spread: https://www.circupool.com/assets/doc/CircuPool-RJ-Troubleshooting-Guide.pdf
 
Production rates should be proportional to amperage (electrons per second). Efficiency plays into it too but first order is amperage.

But 8 amps should be 1.5 lbs per day and not 3 lbs per day.
 
mas985 said:
Production rates should be proportional to amperage (electrons per second). Efficiency plays into it too but first order is amperage.
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Thanks. That 3.0 in 20 minutes in the 550 gallon spa is very close to what I was observing in the larger pool. 9.0 ppm per hour in 550 gallons corresponds to 0.2475 ppm/hour in 20,000 gallons. I was measuring about 0.25. If it was a dwell time issue I'd expect to have seen something closer to half, or 1.5 ppm in 20 minutes.
 
Something doesn't add up for me.
  1. 6.5A x 24 hours is 156Ah.
  2. 1 mole of electrons is 26.8Ah (96,485 Coulombs).
  3. 156Ah / 26.8Ah = 5.82 mol e-
  4. 1 mole of CL2 requires 2 moles of electrons to produce (two Cl- anions).
  5. 5.82 moles of electrons produces 2.91 moles of Cl2.
  6. The molar mass of Cl2 is 70.906 g/mol.
  7. 2.91 moles of Cl2 is 206 g, or 0.45 lbs.
An electrode pulling 6.5A for 24 hours should only be able to produce 0.45 lbs of chlorine per day, and that's assuming all electrons involve a chloride anion. Where am I going wrong? It's even worse if we're generating ClO2.
 

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Because it's not 6.5 amps.....that's the current as read from the power supply side. These are Bipolar Cells ... in other words, only the two outer plates are connected to the power supply (sometimes it's the middle plate and the two end plates are grounded) and so the anode and cathode get mirrored by the current flowing in the powered plates. In effect, the SWG cell acts like a step-down transformer - the voltage drop across each plate is smaller (20.5V divided by 12 cells) but the induced current flowing into each cathode/anode pair is higher. Overall power (energy) is conserved. So in effect you take your 0.45lbs and multiply it by roughly 6.5 and you get a number close to 3 lbs. There are efficiencies based on the area of the cell and the spacing that determines how much voltage drop you need across each cell AND the power applied is a rectified AC waveform so I believe you have to calculate peak currents as the displayed value is likely RMS current and voltage.

This is why I said I did not want to belabor the post with lots of details...
 
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JoyfulNoise said:
This is why I said I did not want to belabor the post with lots of details...
Click to expand...
Thank you for the detailed explanation. I like to understand things. I find a thorough understanding allows my mind to come up with better solutions and/or troubleshooting. I love diving in on the deep end section of this forum.

Are there any hypothetical scenarios where a cell can draw 6.5A and not be generating the amount of chlorine it should? Just hypothetically speaking, I can imagine one or more plates could be shorted and it would reduce the multiplying effect you describe. I guess I'm just hunting for things to rule out. If know what the failure modes look like I can systematically rule them out on my own.
 
I think you can make this work.. :)

Here is your picture, It looks like the pipe is 1.5 inch.
2020-08-05-08_01_45-img_20200805_074544-jpg-photos-jpg.156819


Buy 8 of these to install into your 1.5 inch returns

Amazon.com: Pentair 540035 White Directional Insider Eyeball with 1/2-Inch Opening and 1-1/2-Inch Slip Inlet Replacement, Pool Wall Fittings : Patio, Lawn & Garden

Amazon.com: Pentair 540035 White Directional Insider Eyeball with 1/2-Inch Opening and 1-1/2-Inch Slip Inlet Replacement, Pool Wall Fittings : Patio, Lawn & Garden
www.amazon.com

1. Drain the pool down below all your returns and install eyeballs
2. refill pool and enjoy your SWG
 
I'm still not clear on what set of conditions are necessary for my SWG to produce 3.1 lbs. of chlorine (or thereabouts) per 24 hours as measured in the water. Right now a 24-hour runtime gets me about 6 ppm (or about 1 lb of chlorine) as measured in the water. I can't have more runtime than 24 hours in 24 hours, so some other variable has to change. "Eyeballs" have the same size output as my eyeball-less 3/4" pipes, so it can't be that I need more flow restriction. All that I can see left is water velocity, which affects contact time. Is that the general consensus here?

Just trying to understand the upshot of this thread and turn it into concrete action.
 
Using the head curve for your A pump and assuming the pressure is correct (it seems a bit low), the flow rate should be around 96 GPM which is pretty high. One way to confirm if it is due to the flow rate is to use your return valve and restriction the flow out of the pump. That is a very high head pump so you are going to need to do a lot of restriction to get the flow rate down. Restricting the valve so the filter pressure goes to 34 PSI, will reduce the flow rate to 48 GPM (half flow rate).

BTW, are there any pockets of air that remain in the cell?
 
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Is it normal for the controller power light to be on with no other lights on when it's set at 100%? I confirmed cell Amps and cell current were 000 and no other lights illuminated on the unit.

I turned it on to do a test and after about 3 minutes the bubbles stopped coming from the returns and I found the unit in that state. It resumed on it's own after about 5 minutes. I'm wondering if it's cycling like that, causing the low readings I'm seeing. I guess I have to set up a lawn chair and watch it for awhile.
 
I can't restrict the pump's flow. I can only divert it from pool to spa in varying degrees. I could adjust the suction and returns so little was flowing from/to the pool, but the remainder would be circulating in the spa. The flow rate through the cell would remain the same. I don't think that will help for testing purposes.

No air pockets in the cell.

I did manage to find something to plug one of the returns to increase the water velocity as it exits the other returns to simulate restricting all of the returns by some degree. Now the bubbles shoot out from the returns a few feet into the pool before rising. The pump is currently running for one hour. If this has no effect we'll see the usual 0.2 ppm increase. If it miraculously solved the problem we should see about 0.6 - 0.8.
 

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