Salt level discrepancy ... sanity check

[jblizzle]

Finally got around to installing the Hayward ProLogic P4 and dug the brand new and unopened T-15 cell out of the closet that I bought 3 years ago.

I have the Taylor K-1766 salt test kit (also about 3 years old, stored in my closet).

A few weeks ago, I measured my salt level at 1200ppm (a little surprised at this given that most of the water was new in March and I had measured 600ppm back in April) and then went and bought some salt. Added 200 lbs during a birthday party (girls liked the "diamond day") and the next day measured 2500ppm ... right on what I expected.

Saturday I tested again and got 2500ppm, fired up the ProLogic and it was reporting 2000ppm. Had "diamond day" part 2 with the last 3 bags of salt I had (SWG off).

Sunday tested and got 3200ppm, as expected, but the ProLogic is showing around 2600ppm and does not want to generate. Left the SWG off and then had it check again this morning and still reporting 2600ppm

So, how similar would one expect the ProLogic and Taylor kits to be? {I thought I had read that the ProLogic may only be good to within 800ppm, which seems a little high to me.}

Is there a way to "reset" the SWG that may result in a better agreement?
Is my brand new 3 year old cell bad?
Or are these results within the respective accuracy that others have seen and I should just add 80lbs more salt to make the SWG happy?

 

[mas985]

I have the AquaLogic and for the last 7 years, it is has been very close to the Taylor kit (+- 100 ppm). However, there are a few things that can throw off the reading besides scale which I assume you checked for. The salt readout is dependent on water temperature and if the water temperature changes rapidly, it takes a little while for the readout to re-stabilize to the correct value. So for example, when solar turns on and the water is really hot, the salt readout can be way off (high) but it usually comes back to the correct value in a few minutes. One other thing, the instantaneous salt value seems to be more accurate than the average readout. But a low salt level readout is usually due to a dirty cell.

 

[jblizzle]

Well that is a little disheartening that yours match so well.
The cell was literally just taken out of the box and installed ... brand new (sat in package for 3 years) ... hope it is not bad as it is certainly out of warranty.
Have not been running solar, so no big temp swings.
The instantaneous and average levels seem to match at about 2600ppm.

Makes me suspicious that something in the "software" has not decided that 3 years is old enough and that it now should be replace ... even though it was never used

 

[mas985]

I am speculating but because it is new, there might be a light coating of something on the cells for protection during storage. Have you tried to hose it down? BTW, what are the readings for volts, amps and water temp. I have a bunch of measurements from mine and I might be able to correlate with one of those to see if there is any difference.

Also, on the drop kit, you are going by the first drop that changes the color to salmon? It is pretty easy to overshoot that.

 

[jblizzle]

Yeah I was kind of wondering if maybe the cells were coated or started to oxidize sitting in the closet.

I will get some readings tonight and would be great to compare them to your data.

 

[jblizzle]

Just went out and got a few reading. Here is what it settled to after switching the polarity a few times:

+26.25V +6.30A 84deg 2600ppm
-26.25V -6.42A 83deg 2600ppm
+26.25V +6.46A 83deg 2700ppm
-26.25V +6.52A 83deg 2700ppm

I did not stand there for too long for each reading ... was there any other data I should be able to get?

 

[mas985]

Ok, this is interesting. My water temp is actually close to yours and my salt level is about 3000 PPM. Here are some of my values:

-25.80v -6.30A 82deg 3000ppm
+25.64v +6.32A 82deg 3000ppm

I also fit all of my measurements to a formula that can predict salt levels and your volts, amps and water temp, predicts a salt level of around 3100ppm which is close to the drop kit. So it would appear that volts and amps for your unit are correct but the read out of the display is lower than what it should be so it seems to be the conversion of the V, A & T to salt level which is incorrect but I cannot think of a reason why that would be.

One other question, I would assume that you have a separate water temperature sensor. Does it read a different temperature than the cell?

As far as I know, the controller only uses the cell temp for the calculation but just make sure all the sensors are to the correct ports and are reading correct values.

 

[jblizzle]

Well, the water temp sensor is a little different from the cell temp sensor ... I think the water temp is more accurate based on my thermometer in the skimmer. At this point I have never left the cell on for more than a few minutes. Today I decided to leave the cell on at 10% to see if it just needed "on time" to get straightened out.

So does the controller use the temp and the voltage/amp readings to then estimate the salt level? Odd that it would not follow your correlation.

Some more numbers from this morning:
-26.57v -6.09A 81deg 2500ppm
+26.41v +6.42A 81deg 2700ppm
-26[s:da1yv39r]4[/s:da1yv39r].40v -6.32A 81deg 2700ppm
-26[s:da1yv39r]4[/s:da1yv39r].41v -6.34A 81deg 2600ppm

Other water temp sensor was giving 84deg, which seems more correct to me. Oddly the air temp sensor was already reading 104deg (no sun on it) but I am pretty sure it was not over 100 yet.

EDIT: Fixed typo in voltages

 

[mas985]

Could the wires in the air and solar sensors be swapped? The solar sensor would probably read that high. That shouldn't affect the salt reading though.

And yes, the controller uses the volts, amps and water temp to calculate the salt level. Similar to a compensating TDS meter.

But the difference in the voltage in your latest set of numbers is quite interesting, unless that is a typo. Normally the voltage is fairly constant and a two volt change is pretty significant and something to watch.

Also, I assume that the controller is not delivering an alarm? If not, just let the SWG run normally and see if you are getting the chlorine that you should expect. For your size pool, the cell should deliver about 0.4 ppm of CL per hour of SWG run time. A night run might be better to eliminate UV extinction.

 

[jblizzle]

I do not have the solar sensor installed yet ... it is hot, just not quite that hot

Oops, yes that is a typo ... I will fix it.

It has the check salt light on and a Low Salt error message. The brief times I have let it run, even with the error message, I certainly see the bubbles entering the pool (actually more and larger than I expected to see).

I sent an email to Hayward to see what they may have to say or suggest ... given some reading online, I do not hold my breathe for anything useful to come out of them. It would certainly be nice to see a table of the V/A/Temp correlation to the salt level.

 

[mas985]

If you are running on low speed, the bubbles will be larger than on high speed because they seem to accumulate more before coming out the returns.

 

[jblizzle]

I think that is what I have seen ... fewer larger bubbles on low and then more smaller ones on high ... although still nothing like the "fog" that we have seen some SWG cause. The bubbles are around pea sized I think.

Anyway, I have only observed it running for a total of a few minutes over the last 5 days and have left the SWG off most of the time due to the low salt error and confusion.

 

[jblizzle]

Got a response from Hayward who just quoted me information from the manual ... almost seems like they did not even read all the details I had in my query. Basically said make sure you have the right cell type set (duh) and if the salt reads different than what you think, contact a service provider ... great, thanks for the technical help from the "techsupport"

 

[chiefwej]

Actually my neighbor put in a brand new T-15 cell and was getting strange salt readings. A further exam showed that for some reason the panel had reset itself to a T-9 cell. We changed the setting back to T-15, problem solved. That may be a common problem. Make sure you check it. I wasn't even aware it could happen, since my control unit is so old that it doesn't even have the software to work with anything other than the T-15.

 

[jblizzle]

Well, I know it was defaulted to T15 when I ran through the setup ... so I did check it. I will confirm it is still set that way. Maybe even change it to something else, run the cell, and then change it back and see if I manage to flip a 0 to a 1 or vice versa somewhere on the board.

@ chiefwej, you see my PM? Does your cell temp read higher or lower than your water temp?

 

[chiefwej]

Higher, check your PM for my full response.

 

[jblizzle]

Got ya. So you only really see a temp delta with the solar is running ... mine will be the same way, just not running solar now. Odd that my cell is 3 degree less than the water sensor ... and this morning the sun was not yet on the pad to affect the readings.

 

[mas985]

I will get a little bit of a difference (<2 deg) when the sun is shinning on the cell. It seems to have less isolation than the water sensor.

 

[Thimble]

see if I manage to flip a 0 to a 1 or vice versa somewhere on the board.

Although I don't have the ProLogic P4, my controller will display saturation levels even switched to "off". If yours does the same, then it truly isn't off, more like asleep. Maybe you could try a complete power disconnect via the breaker box (and checking there isn't a battery on the motherboard somewhere) to lobotomize the controller and start completely fresh. Might flip those 0's and 1's around to reality.

 

[jblizzle]

Last night I verified that the cell was indeed set to T-15. I then switched it to the T-9 and turned the SWG to see what happens. Got these numbers:
+25.78V +6.54A 86deg 4100ppm
-25.75V -6.50A 85deg 4100ppm

I then switched it back to the T-15 and also "saved" an instant salt level of 3100ppm as the average {looking at it this morning, the average had dropped back down to 2800ppm} Got these last night right after switching the cell back:
+25.78V +6.51A 84deg 2800ppm
-25.78V -6.62A 84deg 2800ppm

This morning I saw this:
+26.33V +6.02A 80deg 2600ppm

First, I am a little surprised the difference in the temperatures as I do not think the water temp really swung that much (no solar active)

Second, seeing the higher salt level with the T-9 setting was interesting. This leads me to wonder if one could not prolong the life of their cell (at a lower capacity) by just switching to the T-9 setting from the T-15 setting when the cell was starting to read lower salt levels than reality. Instead of raising the salt level extra high to trick the cell to keep working, might be as simple as switching the setting and the "higher" salt reading might actually be in range and closer to reality.

Of course none of this helps me decide if I have a "serious" equipment problem, or if mine is just not calibrated as well for some reason, or if my readings are still within acceptable bounds and I should just add more salt and be done with it. I may try calling Hayward and seeing if the phone tech support is better than the email tech support.

Side note, is the instant salt of the average salt value used for the error code. I did not see an error code this morning for low salt even though the instant was showing 2600ppm ... this leads me to believe the average level of 2800ppm was being used for the error check and as this drops to the instant reading I am likely to see the error pop up again.