Question about swg performance

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J

jan verbeem

Well-known member
May 26, 2016
46
Thailand
I have a 35grm chlorinator, which has about 8000 operating hours, and seems to be on his last legs.

Troubleshooter says that a properly functioning cell should output between 21-24V and 7.2A.

My cell measures 18.5V and 7.2-7.5A with a salt level of ~5000ppm.

Now the strange thing is that when I dilute the salt content, by adding fresh water to the flow going through the cell, the output voltage will increase to about 19.5V, while the current stays about the same.

When I increase the salt level to +6000ppm, the output voltage will decrease to below 18V, with the current again staying stable. I would thing that it should just be the opposite, with higher salt level also higher output voltage.

I have tried a new cell, and the behavior is exactly same.

Can anyone explain this?
 
It simply Ohm's Law -

V = I R

The power supplies for all SWGs are constant current (I) source. The power supply maintains a constant current and let's the voltage vary in response to the circuit resistance (R). The resistance of the circuit is directly proportional to the conductivity (1/R) of the water flowing through the cell plates. The conductivity of water increases when you add salt which means the circuit resistance decreases and, as such, the drive voltage necessary to run the cell decreases.

Voltage is somewhat meaningless to an electrolytic cell because current is electrical charge delivered per unit time. Every electron delivered is what converts chloride to chlorine and so it is absolutely critical to maintain a constant current so that the cell produces a constant amount of chlorine.
 
JoyfulNoise said:
It simply Ohm's Law -

V = I R

The power supplies for all SWGs are constant current (I) source. The power supply maintains a constant current and let's the voltage vary in response to the circuit resistance (R). The resistance of the circuit is directly proportional to the conductivity (1/R) of the water flowing through the cell plates. The conductivity of water increases when you add salt which means the circuit resistance decreases and, as such, the drive voltage necessary to run the cell decreases.

Voltage is somewhat meaningless to an electrolytic cell because current is electrical charge delivered per unit time. Every electron delivered is what converts chloride to chlorine and so it is absolutely critical to maintain a constant current so that the cell produces a constant amount of chlorine.
Click to expand...

Thanks for the excellent explanation.

The manufacturers troubleshooter states that the voltage should be between 21 -24V, so I assume anything lower than that means the cell is bad.

The new cell, which is a generic one, outputs almost 1V less than the old cell under each scenario.

Current is same for both cells, and at manufacturers specification.

Do you think this indicates that the new generic cell is of inferior quality, or should I look further than that, like issues with the power supply?
 
Again, it depends on the salinity of your pool water. What is your current salt level as measured by an independent salt test (like the Taylor K-1766)? Is your salinity level within spec for your SWG?
 
Salinty should be between 4000 and 7000ppm, my digital tester says 6200ppm.

And this is what the troubleshooter says.

5.
Switch onchlorine production on theTRi unit (‘On/Off’switch) and set chlorine output at 100% (‘Scroll’switch).
Ensure that the fan at the back of the control box is running
.
Check cell supply (mark #1) There are2 possible cases
:
-
Cell voltage is between 21 and24 V DC = no problem with TRi unit
-
Cell voltage is out of those previous values= nominal amperage problem
,
go to next step

Nominal amaperage should be 7.2A according to the troubleshooter, and mine fluctuates between 7.2 and 7.4A, so I assume that is fine.
.
 
Is your SWG producing chlorine? The way to check is to put it up to 100% output and, when bubbles start to come out of the returns, try to take a water sample directly from the return water. It should be highly chlorinated and turn whatever chlorine test you are using it's brightest color.

A voltage drop can be caused by lots of different things up to and including faulty control electronics. Normally zero volts with high amps would indicate that there is a short in the cell. If possible, perhaps you should pull the cell out and inspect it. Even if there is no white calcium scale, it might be worthwhile to perform whatever is the recommended cleaning on the cell.

However, at the end of the day, if you're still seeing such a minor voltage drop and your chlorinator is producing chlorine, I would just leave it alone. It's working and there's no sense in fiddling with it.
 
My cell housing is clear plastic, and can see the cell producing chlorine gas. The voltage drop is with both cells, the old one and the new one.

The new one currently produces 15.9V, which I don't consider a minor drop, while the old one produces about 17V.

But the strange thing is that the higher the salt content, the lower the voltage output is, which I thought should be just the other way around.
 
Some SWGs maintain the current at a fixed number of amps by adjusting the voltage as needed. At higher water temperature and/or salinity the voltage is reduced by the power supply. At lower water temperature and/or salinity, the voltage is increased. The Intellichlor works like this. I think that the Aquapure and Autopilot also work like this.

Some SWGs provide a fixed voltage and allow the current to vary depending on the water temperature and salinity. The Hayward Aquarite works like this. Even though the voltage is fixed, it will vary depending on the load in amps. The higher the amps, the greater the voltage drop.
 
JamesW said:
Some SWGs maintain the current at a fixed number of amps by adjusting the voltage as needed. At higher water temperature and/or salinity the voltage is reduced by the power supply. At lower water temperature and/or salinity, the voltage is increased. The Intellichlor works like this. I think that the Aquapure and Autopilot also work like this.

Some SWGs provide a fixed voltage and allow the current to vary depending on the water temperature and salinity. The Hayward Aquarite works like this. Even though the voltage is fixed, it will vary depending on the load in amps. The higher the amps, the greater the voltage drop.
Click to expand...

Thanks for the response, that would explain the lower voltage after I added more salt, but I think that is also what the manufacturer means when he says 21 - 24V in the troubleshooter.

So my cells, also the new one, are considered way out of range with the 16V.

Is there a way to test the performance of a cell other then by measuring the voltage?
 

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Since the current output of my cell is slightly higher than the manufacturer recommendation, about 7.5A where manufacturer says 7.2A, and it can be adjusted manually by a potentiometer on the back, is it possible that the 0.3A causes the voltage drop?
 
I got an update.

I managed to get a replacement Zodiac Tri unit, with 800 operational hours on the clock, from a friend, complete with cell wiring.

When connected to the new and old salt cell it reads the exact same output voltages.

That is 16.9V for the old cell and 15.9V for the new cell. Current output is 7.40A.

It should actually read between 21 and 24 volt, according to the repair manual.

http://www.vagnerpool.com/web/download/12408

The biggest mystery to me is why the new cell reads a lower output voltage than the old one. Logically it should be the opposite.
 
The amps determine how much chlorine is being produced. Since your amps are correct, your unit is producing the correct amount of chlorine. Not sure why your voltage is off.

Is your supply voltage correct?

Are you measuring volts dc to the cell?
 
There must be a reason why they say in the repair manual that output voltage should be 21-24V, but both units give the same output voltage. I have also read that when a cell is end of life that the output voltage will decrease, so the new cell should at least produce a higher voltage than the old one, not lower as is the case.

My supply voltage is 220 -225V, and yes I'm measuring DC Volts and DC Amp.

Zodiac.jpgZodiac 2.jpg
 
Not sure how much the frequency matters. Just trying to check as much as possible. Some units adjust voltage to keep the current the same. I don't know how yours works.

Probably need to check with Zodiac.
 
That is how mine works, since the current is a fixed figure, but from the repair manual I understand that the fluctuation of the voltage should be limited between 21 and 24V.

I have emailed Zodiac already, but no answer forthcoming yet.
 

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