Does a salt cell require higher chlorinator % setting as it gets older to maintain same FC level?

[kalW]

Hi everyone!

This is not a "what should my salt cell chlorinator output % be set to" question. I understand all that and vary the % throughout the season and maintain levels correctly per my CYA / bather load / etc.

What I'm curious about is as a cell ages does it require a higher chlorinator % setting to maintain the same output? I'm (I believe) on the last legs of my T-CELL-9 and my usual chlorinator % I'd use given the same time of year in past years I've noticed has been going up. In fact, I just opened the pool and with my cell set to 10% I almost immediately got "percentage met" but am measuring 0% chlorine. Kept bumping it up as high as 50% and still getting "percentage met" after a few minutes. No cell can supply that much chlorine in minutes of course, but more importantly the pool FC level shows close to 0 ppm.

Super Chlorinate (100%) works however. Measuring a water sample coming out of a return shows there's chlorine produced and the voltage and amp cell numbers are within range in both polarities as it's producing Cl (see pics below). My understanding is that the amps will drop as the cell gets older but it's been the same for a few years now. Adding a set amount of salt also brings the salt ppm up as expect/measured by the cell so the cell seems to be "working". (For my pool 5kg has always bumped my salt up by 100ppm, I'm not getting "low salt").

I'm currently running a 3 hour super chlorinate now which should bring me close to my target FC ppm, then I'll see what % chlorinator I need to "maintain" that 2-3 ppm of FC. Hopefully it's not 100% as it's the start of the season and I have nowhere higher to go. Just curious if it's normal that you need to bump the chlorinator % output go up as the cell ages. Cell visually looked ok when I checked ~12 months ago. I've never needed an acid wash. Thanks!

Kal





Note: My understanding that when a cell is on current should be between ~2.3 to 6.7 amps and voltage should be between 22-25V. My voltage has always been a bit higher than that.

 

[wireform]

Did you test the water to see what you have, Perhaps what it's producing is getting used immediately by algae.

 

[kalW]

Did you test the water to see what you have, Perhaps what it's producing is getting used immediately by algae.

Thanks for the reply!

No - I opened last week, tested the water, balanced it. It's perfect. Water is perfectly clear and has always been as I shock it before closing and then dose it with bleach even before we open. The pool's never had algae in the 10 years we've had it. It never opens green, is always perfectly clear. I tend to keep the cell off when the water's colder and just dose with bleach at the very start of the season as it's easier on the cell (the current water temp of 57F is actually a bit colder than I'd normally run a cell at).

I think too that if there was algae using up the chlorine the cell would just stay on and not show "percentage met", no?

Some pics I just took:





Kal

 

[proavia]

Post a full set of current results from your TF-100

FC
CC
pH
TA
CH
CYA
Salt
Water temperature.

The SWG is not a smart device. It doesn't measure chlorine content.
If you set the SWG to 35%, it runs full bore for 35% of its cycle.
For example, if its cycle were 10 minutes the SWG would be ON for 3.5 minutes and OFF for 6.5 minutes.
Different brands of SWG's have different cycle lengths.

 

[JoyfulNoise]

@mas985 has been experimenting with using “old” cells to produce chlorine by simply running them beyond the point at which the controller shuts them down. Turns out they’ll continue to produce a fair amount of chlorine even at advanced age.

 

[mas985]

What I'm curious about is as a cell ages does it require a higher chlorinator % setting to maintain the same output?

Yes

I'm (I believe) on the last legs of my T-CELL-9 and my usual chlorinator % I'd use given the same time of year in past years I've noticed has been going up. In fact, I just opened the pool and with my cell set to 10% I almost immediately got "percentage met" but am measuring 0% chlorine. Kept bumping it up as high as 50% and still getting "percentage met" after a few minutes. No cell can supply that much chlorine in minutes of course, but more importantly the pool FC level shows close to 0 ppm.

At 50%, the cell should run for 90 minutes. You might want to time that. Which controller do you have?

Also, if you are comparing between previous years, you MUST have exactly the same CYA level or the numbers can't really be compared.

Super Chlorinate (100%) works however. Measuring a water sample coming out of a return shows there's chlorine produced and the voltage and amp cell numbers are within range in both polarities as it's producing Cl (see pics below). My understanding is that the amps will drop as the cell gets older but it's been the same for a few years now. Adding a set amount of salt also brings the salt ppm up as expect/measured by the cell so the cell seems to be "working". (For my pool 5kg has always bumped my salt up by 100ppm, I'm not getting "low salt").

What does an independent Taylor drop test say is the salt level?

I'm currently running a 3 hour super chlorinate now which should bring me close to my target FC ppm, then I'll see what % chlorinator I need to "maintain" that 2-3 ppm of FC. Hopefully it's not 100% as it's the start of the season and I have nowhere higher to go. Just curious if it's normal that you need to bump the chlorinator % output go up as the cell ages. Cell visually looked ok when I checked ~12 months ago. I've never needed an acid wash. Thanks!

Under optimal conditions and assuming your pool volume is correct the T-9 produces 0.98 lbs/day which is about 9.25 ppm for a 24 hr 100% run. 3 hours 100%, is 1.15 ppm rise. I would run it until you get a FC that is 10% of the CYA level. BTW, what is your CYA level?

 

[Mdragger88]

You said your levels are perfect but pool has 0 fc. It won’t stay clear for long that way.
Until you get your cell figured out you need to dose with liquid chlorine to target levels ASAP.
See—> FC/CYA Levels
Do not wait on the cell to raise the fc to adequate levels. It simply takes too long & nasties grow in the meantime.
No need to play roulette with your water to troubleshoot your swcg.

As mentioned above your swcg doesn’t detect chlorine produced - the “percentage met message” doesn’t mean it has measured fc.
Here’s an explanation

Chlorinator off percentage met ??

Hello there? I'm hoping someone can help me understand my new equipment. My pool is only a few months old and I've taken over the maintenance from the pool company. Every single day I go out to my control panel I see this message (see picture) I have done so much reading and can't figure out...

www.troublefreepool.com

 

[PoolStored]

Have you checked your CYA? It is usually lower in the spring because of rain, snow and degradation. It may be that your usage is up because CYA is lower than you normally have???

Sorry, MAS985 caught it in post #6...I missed it...

 

[kalW]

Post a full set of current results from your TF-100

FC
CC
pH
TA
CH
CYA
Salt
Water temperature.

The SWG is not a smart device. It doesn't measure chlorine content.
If you set the SWG to 35%, it runs full bore for 35% of its cycle.
For example, if its cycle were 10 minutes the SWG would be ON for 3.5 minutes and OFF for 6.5 minutes.
Different brands of SWG's have different cycle lengths.

Water's (other than FC) is exactly where I want it and how I've run it for the last 9 seasons:

FC: 1-2 ppm now after running after super chlorinate for 3 hours. Normally I like this at 3-4 ppm and will play with the chlorinator % to maintain it. I was 0 ppm before I ran super chlorinate because I stopped dosing the pool with bleach to maintain a bit of chlorine. The pool just recently got above 50F. Below 50F not much grows so I'm not overly fussy about it. Today the pool is finally close to 60F so I figured I'd start using the cell and stop dosing it with bleach.

The other numbers today are all where I want them:

CC: 0
pH: 7.5
TA: 80
CH: 250
CYA: 40 (some may say that's low but it's where I like it with FC at 7-10% of CYA)
Salt: 3200 (before super chlorinate - will have dropped slightly after)
Water temperature: 57F

After more testing I've noticed that turning the chlorinator to 100% doesn't cause the cell to kick on (you hear it). The only way I can get the cell to kick on is to turn on super-chlorinate. I'm curious now if that's a board/controller issue, or if that's just how cells behave when they get old? Isn't super-chlorinate the same as turning the chlorinator up to 100% for 3 hours? I.e. Why does super-chlorinate work but not setting the chlorinator to 100%?

Kal

 

[kalW]

At 50%, the cell should run for 90 minutes. You might want to time that. Which controller do you have?

Hayward PL-PS-4-CUL, firmware 4.45.

Also, if you are comparing between previous years, you MUST have exactly the same CYA level or the numbers can't really be compared.

Agreed.

What does an independent Taylor drop test say is the salt level?

I don't have an independant drop test unfortunately. Not this is is scientific really but when I ran a super-chlorinate 3 days ago for a few seconds to have the cell kick on and measure the salt level - it was 2200 ppm. I then added salt to get up to ~3200 ppm per my usual calculator and the new measured result from the cell agreed (3200 ppm) after some recirculation and more importantly the amount of salt added was identical as every other year.

Under optimal conditions and assuming your pool volume is correct the T-9 produces 0.98 lbs/day which is about 9.25 ppm for a 24 hr 100% run. 3 hours 100%, is 1.15 ppm rise. I would run it until you get a FC that is 10% of the CYA level. BTW, what is your CYA level?

Yup. Around 3-4 ppm FC as my CYA is 40. I'll either keep running super-chlorinate to rise it 1.15 ppm or so every so often, or dose it with bleach to keep some FC in there as I don't want it to turn green. It's 57F and we live in a colder climate than probably most here (Ottawa Canada) so it won't turn green fast.

Given that cell won't kick on even with the chlorinator set to 100% I'm starting to think a new cell is in the cards. It's going into it's 9th season so it's lived its life. Odd that running super-chlorinate works however. That's the only part I don't get I would figure super-chlorinate is simply running the cell at 100% for 3 hours.

Kal

 

[proavia]

It's your pool and you can run it the way you wish - however, you are inviting algae at those low FC levels.
Skirting minimum FC for a given CYA is tempting fate.

Use liquid chlorine anytime the SWG can't keep the pool chlorinated. And use the non-SWG FC/CYA chart whenever dosing with liquid chlorine. It is safe to swim with FC between minimum and SLAM level for your CYA.

 

[kalW]

As mentioned above your swcg doesn’t detect chlorine produced - the “percentage met message” doesn’t mean it has measured fc.
Here’s an explanation

Chlorinator off percentage met ??

Hello there? I'm hoping someone can help me understand my new equipment. My pool is only a few months old and I've taken over the maintenance from the pool company. Every single day I go out to my control panel I see this message (see picture) I have done so much reading and can't figure out...

www.troublefreepool.com

Err, wait a second. I think I misunderstood previously...

So if I run super-chlorinate for ~3 hours and then turn the cell up to 100% it's normal that the cell won't kick on as the controller may think that the cell has "completed" it's duty cycle already? Anyone know how long the duty cycle for a Hayward PL-PS-4-CUL (Firmware 4.45) is? The manual doesn't state.

I'm thinking I should simply add some bleach to get to my 3-4 ppm FC and then set my cell chlorinator % to what I normally do this time of year to "maintain" that 3-4 ppm PC.

Kal

 

[kalW]

It's your pool and you can run it the way you wish - however, you are inviting algae at those low FC levels.
Skirting minimum FC for a given CYA is tempting fate.

I do agree with this - lower CYA with matching FC makes it easier to SLAM if you have to. Though that's a bit of a catch-22 I suppose as if don't let your FC (or ratio of CYA to FC) drop too much you won't ever need to SLAM.

10th season now and never seen it ever be green (even at opening) so maybe I'm lucky. I'm fairly meticulous with ensuring there's FC in there...

Kal

 

[proavia]

I do agree with this - lower CYA with matching FC makes it easier to SLAM if you have to. Though that's a bit of a catch-22 I suppose as if don't let your FC (or ratio of CYA to FC) drop too much you won't ever need to SLAM.

10th season now and never seen it ever be green (even at opening) so maybe I'm lucky. I'm fairly meticulous with ensuring there's FC in there...

Kal

If you maintain your pool using TFP methods, you will never need to SLAM.

But if you did need to SLAM at SWG recommended CYA levels it's only the initial chlorine dose that will take a bit more chlorine. Once the FC is close to SLAM level it will decrease about the same amount while killing algae no matter if CYA level is at 30 or 70.

The higher recommended CYA for SWG also allows the SWG to run less or at a lower percentage then a lower CYA level. The recommended FC/CYA levels provide a good balance for the listed chlorination types.

 

[wireform]

Super chlorinated is basically a 24 hour timer and then it'll revert to the normal percentage on the other hand 100% means non-stop till you change it but while they're both running its the same output.

 

[kalW]

Well this morning I turned on the pool filtration after it had been off for a few hours and the cell is showing output with the chlorinator set to 25%. So seems all is normal in that if you turn it the chlorinator up to 100% immediately after running a super-chlorinate (100%) the cell won't kick on. Not sure why really. Odd.

I also wasn't aware that a cell is either 100% on or off and that that the chlorinator percentage is a duty cycle setting and not an actual output setting (ie. set to 50% it'll run the cell at 100% for half the cycle then off for the second half). The manual doesn't mention this. It makes sense in retrospect as the diagnostic voltage/current do not change based on chlorinator %. If the system was in some way actually measuring how much FC ppm you have flowing through then they'd give you the means to just set the ppm you want and not a percentage (like some of the self-dosing setups).

Thanks for the help everyone! Still curious what the cell duty cycle time is on a Hayward PL-PS-4-CUL (firmware 4.45) if anyone knows.

Cheers and happy swimming!

Kal

 

[mknauss]

Still curious what the cell duty cycle time is on a Hayward

180 minutes

 

[kalW]

Thank you! I'll write that in the manual!

Kal