Calibrating an AutoPilot salt sensor

[smallpooldad]

Split off of Pool Pilot Dig220 Salt Level reading way off. JasonLion

On my Pool Pilot unit I have to manually input the salt level, could this be the salt level issue? If you are unsure of how to input manually call their help desk, they are very helpful. Of course your unit could be different and it could simply be reading wrongly and need repairing.

I also have an adjustment for the pH and setting this correctly seems to adjust the salt level as well but not by much, not all units have this feature.

The algae issue may (and I am definetly not sure of this) be caused by under production of chlorine due to the high salt level the unit thinks it has; when in fact, as you point out, it does not have this high a level of salt. Check with the help desk as I could be completely wrong on this.

Once you have checked the level of salt as everyone points out with a proper test kit, you may indeed have 6500 ppm. The help desk tech told me the ideal level for my Pool Pilot model is 3200 - 3300 ppm, even though the manual states 3,000 ppm, yours off course could be different. Some units can of course operate with levels up to 35,000 but when mine was at 6,500 by accident and my inputed reading was 3,200 it either under or over produced but I cannot remember which. as I quickly brought it back to 3200 by draining down half the pool water and refilling with fresh water.

Some units may only be able to operate up to 5,000, I am guessing here, but if this is the case for your unit that may be the issue.

In any event after getting a good reading I would call the help desk they are very helpful.

As regards algae you really need proper readings from a good test kit such Taylor's, it could be that your CyA is too low (under 25 -30) or too high (over 100). As you reduced the size of your cell I am not sure based on your daily chlorine loss what percentage you need to set it at, it would have to be higher than your old SC-48, but if that number has to be over 70% then you will ideally need to run your pump longer or get a bigger cell. If you are still running it at the old cells percentage it is most probably too low and could be the cause of your algae issues.

Good Luck.

 

[JasonLion]

Re: Pool Pilot Dig220 Salt Level reading way off

AutoPilot units are fine with salt levels anywhere from around 2,500 to salt saturated brine (above 50,000). Other parts of the pool may have problems when the salt level gets too high, but it won't bother the AutoPilot unit. Other brands often have an upper limit on salt level, but that isn't relevant here.

smallpooldad, if you need to manually input the salt level then your unit is broken. Perhaps you are misunderstanding how the salt calibration works and think that you are entering a level when you are actually calibrating, or more likely mis-calibrating, the sensor.

coronapoolguy's unit does not have a PH sensor.

 

[smallpooldad]

Re: Pool Pilot Dig220 Salt Level reading way off

JasonLion,

Firstly apologies my ppm was not as previously stated I looked at my pool diary and it was 4500 ppm so I think this may be the where I confused you.

I think your reply was very valid and I do think that there is a good possibilty that either coronapoolguy's unit is either broken or the test kits he used were either not very accurate or misread and he does indeed have a salt reading of around 6,500 or so. Only time will tell.

In my case the circumstances were somewhat different.

In the Total Control manual on page 34 it states:

"Calibrating the salt sensor.
Note: The unit has been calibrated at the factory and should not need further adjustments. In the event that the salt display does
not match on-site test results, follow these steps:
1. Press MENU, press Δ or ∇ until “Maintenance menu” is displayed, then press SELECT.
2. Press Δ or ∇ until “Calibrate salt” is displayed, then press SELECT.
3. Press Δ or ∇ until the number on the display matches the accurately measured pool sample, then press SELECT. The
maximum adjustment is ± 1000 ppm (1.0 g/l).
4. Press Δ or ∇ until “End menu mode” is displayed, then press SELECT."

At the time I accidently managed to get my real salt level to 4500 ppm versus a measured salt level of 3200 or so on the unit I acheived this over a period of close to a year by checking with my old test kit strips (stupid me) which every few month said I needed to add salt. So I did this and adjusted the unit by about -200 to -300 ppm to compensate, each time I added. Eventually the actual chlorine output was either too high or too low I do not remember and I seeked out answers. On this site or another it stated I should be careful to use new chemicals or strips, preferably two sets to confirm. I ordered both the Taylor salt kit from Taylor and the fresh strips, and low and behold they both agreed on 4500 or there abouts.

So by slowly adjusting the unit I managed to slightly exceed the 1000 ppm maximum adjustment level, thereby inadvertantly exceeding the limit. Although I am aware there is about a 200 ppm leeway on test results so I could have been somewhere close.

My unit is fortunately not broken and now works remarkably well, it is set at 3400 ppm which is a variance of about plus 300 ppm to what it gives when I refill from close to 100 ppm using both Taylor and strips to confirm (new of course). My temperature adjustment is about -4 F and has been ever since I got the unit. The tech at AutoPilot actually told me to adjust the salt when I first installed it as he did with the temperature and stated not worry about the temperature too much.

I now run the pool at about a 4-5 ppm chlorine, with a CyA at about 30-35, the SC-60 unit runs at 24% out put in December rising to 34 -36% in the height of summer, with no problems

My only confusion in what you wrote is this statement "Perhaps you are misunderstanding how the salt calibration works and think that you are entering a level when you are actually calibrating, or more likely mis-calibrating, the sensor."

When I enter the salt calibration I do set the amount at 3400 ppm on my unit by using the up or down arrow and not the adjustment value as I do with the temperature adjust where I enter -4 by using the up or down arrow. As mentioned this is about plus 300 ppm from what the unit gives. I know it is not a lot but the tech preferred me to use the test readings if they agree rather than the units. So I have to admit I am a little confused by your statement that I am "misunderstanding", could you please explain that to me if I am still misunderstanding, it would help me see where I may still be going wrong if indeed I am going wrong, now that I explained what actually happened to me and I might agree it is rather odd but it could easily happen to another who uses old chemicals? But I can certainly see where you might think my SWG reading was broken as I stated 6500 ppm.

So even by Pool Pilots standards one is able to compensate on some units a variance of 1,000 ppm of salt either up or down from their reading to the true reading and this might be part of coronapoolguy's issue, but certainly not all of it. One dead giveaway I did learn from this stupid experience was that higher salt readings in my case created much larger bubbles and not the fine stream I get with with a setting of 3200 to 3400.
.

 

[JasonLion]

You almost never "have to" calibrate the salt sensor, certainly not in the case you describe. 99% of the time you should not be calibrating the salt sensor, as the sensor in the AutoPilot is most likely more accurate than whatever test you are using to calibrate it with. Re-calibrating often leads to problems, just as as you describe. You were trusting the salt test strips, which were probably wrong, and as a result presumably mis-calibrated the salt sensor in the AutoPilot.

Coronapoolguy's issue involves a situation where the AutoPilot and the pool store disagree by far more than the +-1,000 calibration range of the salt sensor. One or the other salt reading is completely wrong. My guess is the pool store is wrong. It is very very common for pool store rest results to be wildly wrong. It is also remotely possible that the AutoPilot sensor electronics are broken. Regardless of which it is, recalibrating the salt sensor will only make things worse. If the pool store is wrong, then recalibrating will make the AutoPilot also be wrong, and if the AutoPilot unit is broken recalibrating won't improve the situation and could easily lead to the illusion that the problem is resolved, while the actual sensor remains broken.

Ultimately, it doesn't matter if the AutoPilot salt reading is right or not except in one rare case. If the AutoPilot is reading lower than actual and the salt level is low to begin with, then the unit will shut down. That is a rare combination, not normally worth worrying about and certainly not applicable to Coronapoolguy's issue. Everything will work with salt levels anywhere in the 3,000 to 7,000 range (or higher). The higher end of that range could lead to some corrosion issues, but would not lead to any of the problems Coronapoolguy describes.

 

[smallpooldad]

JasonLion,

Thank you for the reply. I agree with you that "One or the other salt reading is completely wrong". And I agree with that is most probably the salt reading by the pool store.

I checked my own deviation on the "Setup" Menu to see what my salt variance was and it read -24%, so I called AutoPilot and the tech stated that this would indicate a stuck, or a number of stuck pixels at this variance request only, as -24% would normally mean I was not producing any chlorine. As the unit is producing chlorine he believes it to be stuck pixels so told me not to worry. I could replace the display board but at around $500 or so on the net he felt that as everything else works fine I should just leave it alone. He felt that if I did want to replace the board it would be better to get a whole new power unit on the net as it runs around $700. I am going to wait until something else fails.

I did ask him about adjusting their reading on the salt versus my inputted reading using both fresh salt test strips and the Taylor salt kit. He stated that over time the unit/cell would loose it's factory adjustment and that it would in their experience be better to use my readings rather than the units calculation, this is why they added this feature. Currently the variance is around 300 - 400 ppm with their unit reading lower, the units and SC-60 cell are over 3 years old.

But the key for my situation, as I mentioned before, is a proper salt test kit such as Taylor's and fresh strips to cross check and doing it yourself. My problem before was old strips and no Taylor kit to cross reference against caused my error, luckily I quickly learned my error. I hope I do not appear to be "flogging a dead horse", but my personal experience and AutoPilot's own opinion seems to bear out that it might (please see question below as to "might") be better if one does adjust, albeit ever so slightly.

Thank you for the time you gave to this matter therby pushing me to delve deeper into the answer, my mind is now at rest.

I think the point your are making and I may be wrong is that even though I adjust it, it actually makes no difference to the output whether it reads 300-400 ppm wrong. What I set it at is really only for me to know, so best to leave it alone. Am I correct in that assumption?

If that is the case I thank you as I was not aware of that and am looking forward to your reply, to clear it up.

The only thing I could think of is that if the cell, the SC-60, is only run at "Power Level 2" at not very high percentages, if it did last a very long time, say 6 to 10 years, then the variance might grow over time to conceivably a negative 1000 ppm as the Tech indicated. If the variance eventually reached a level of 1000, a unit reading of 3000 would be an actual true reading of 4000 ppm, then would it not be less efficient? I did not ask him this question on efficiency but it would be interesting to know, especially as they recommend a true reading of 3300 ppm as the most efficient, the water would of course be more salty.

Aloha.

 

[JasonLion]

AutoPilot units fully compensated for any salt level from 2,500 on up. They produce the same amount of chlorine for a given run time & power level across the entire range of allowed salt levels. That is true regardless of how the salt sensor is calibrated, or mis-calibrated, or even if it is out-right broken. There are some small secondary effects of varying salt levels, but none of them make any significant difference to the AutoPilot units. Some of the secondary effects, like the corrosion issue at high salt levels, can be important to the pool owner, but the AutoPilot doesn't really care.

The AutoPilot provides the salt level readout as a convenience to the user. It doesn't directly affect the operation of the unit. For a pool owner, the only significant difference they will see with salt levels between 3,000 and 5,000 is how salty the water tastes. Below 3,000 you run the risk of going too low and having the unit shut off. Above 5,000 there starts to be a small risk of corrosion to some common metals, like copper, in contact with the water; with the risk increasing as the salt level continues to go up.

Note that not all SWG brands are like this. Some other brands care a great deal what the salt level is. When the salt level is out of range they may shut down, overheat, or produce different amounts of chlorine than they would at normal salt levels.

Also, differences in salt levels of +-300 or even +-400 are not really significant to anything unless you were right on the edge of having problems to begin with. Even the best testers designed for home use are +-200, and most of them are +-400. There is lab grade equipment that can do better, but there really isn't any point to getting it for pool use, except as a toy, even if you can afford it. Salt levels will vary over the course of time from rain, evaporation, backwashing, topping off the water level, etc. Small changes in actual salt levels and test results that vary on the same sample by a few hundred are to be expected and really don't mean anything.

 

[Poolsean]

Keep in mind too that the salt accuracy is based on the cleanliness of the salt sensor blades on the tri-sensor, and the amount of loss (of factory adjustment) is not significant, and is based on a very long period of time.
The point is, do not adjust your salt calibration until you have tested the salinity with an accurate tester.
The -24% indicated on the salt calibration indicates how much off the factory calibration the unit has been changed. A simple recalibration, in the Factory Menu, and with a Tri-sensor Simulator, should bring it back to a 0% setting. Again, this should not be much of an issue over the life span of your system.
The rest of Jason's reply is spot on.

The issue with CoronaGuy's unit was that the display is stuck on 6300 ppm and does not allow him to make any adjustments to the salt calibration. Its more than just the inaccuracy of the store test versus his test.

 

[smallpooldad]

JasonLion and Poolsean,

Thank you both for those very clear and concise replies, they were really helpful.

As I stated before I am very pleased with the AutoPilot system and your comments certainly strengthen my already high opinion of this SWG system, also of this website's forum and the two of you.

Have a good weekend.

Aloha.