Low Salt Light On - Salt Not Low!

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phalcon51

phalcon51

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LifeTime Supporter
Oct 5, 2010
203
So. California
Recently the low salt light came on on my IC-40. The cell light is still green and it appears to make chlorine. The salt readings are 3570 with the Aquacheck test strips and an even 4000 with the Taylor 1766 drop test (not sure which one is the more accurate - anybody know?). The water temp in 64deg. F. I know the unit will stop producing chlorine at 52 deg. and below, but will it misread the salt concentration at 64 deg.? Does temperature affect this function? Should I dose up on the salt a little and see if the light goes green? Any problem having it produce chlorine when it thinks the salt is low?

All opinions gratefully accepted :cheers:

Gary
 
The K-1766 measures chloride levels and reports in units of salt (NaCl). That is going to be the most accurate as far as salt is concerned. An electronic tester measures conductivity (which is dependent on the total number of each type of ion) and converts that into a salt reading.

The cell is calibrated at 77 oF. For every 5 degrees below that, the salt will read 200 ppm low. At 64 oF, the salt will read about 520 ppm low. Below 2,900 ppm, the low salt warning light will come on, but the cell will continue to work. Below 2,500 ppm, the cell will shut off.

If the salt is 3,400 ppm, then it could give you the low salt warning light. You could add about 200 ppm to see if that works. However, the cell's ability to produce chlorine is reduced enough that it might be better to use liquid chlorine. Also, if you add too much salt, then when the water warms up, the cell could give the High Salt warning (at 4,000 ppm to 4,500 ppm (exact numbers depend on model number and version)) .

As long as the cell is still producing chlorine, you might just want to use it until it shuts off, or switch to liquid chlorine.

You might want to consider getting the diagnostic wand, which will give you important information that can help you get better performance and diagnose problems.

http://www.americanbestpoolsupply.com/detail/6872.htm ($107.00)

http://www.poolplaza.com/P-PEN-520594-3545.html

pentair-diagnostic-wand-results-t30136.html
 
Thanks for the info. One last question: it's been just abut 3 mos. since I cleaned the unit (the recommended cleaning interval) but the pool has seen very little use and chlorine levels have been fairly stable. If it is in need of cleaning could this also cause it to read low and turn on the low salt light? I've been able to run it constantly for the past year and didn't have this problem. I'm pretty sure the water reached this temp sometime during last winter without turning on the low salt light.

Gary
 
A quick addendum to my last post:

I just found the owner's manual and it states the following:

"If the salinity is below 2600 ppm, the salt display will light the red LOW SALT indicator, and the CELL light will go blank, indicating there is not enough salt in the pool for chlorine to be produced."

and

"If the red LOW LED salt light is on, no chlorine is being produced. Add salt to the pool water"

In addition, it also states:

"Red LED: Low salt. The water salt level is below 2800 ppm. The IECG will be producing chlorine at reduced efficiency. It is highly
recommended to add salt"

So in my case, with the salt level at a minimum of 3570, even accounting for the drop in temp causing a drop in the system reading of 550 ppm, this leaves a reading of 3050, still above the 2800 ppm level that would kick in the low salt LED.

So, the red low salt light is on, but the green Cell light is also on and it appears to be producing chlorine, i.e. a fair amount of bubbles come out of the return lines when the cell light is on and no bubbles appear when the cell light is off.

Is this abnormal behavior to have the low salt light on at 3050 ppm (or higher), yet still have the green cell light lit and be producing chlorine?

Thanks again for your help.

Gary
 
If the "Low Salt" light is flashing red, then the sensor is calculating the salt to be between 2,600 and 2,800 ppm and it wants you to add salt, but it should continue to work. If the Cell light is solid green, then it is working.

If the "Low Salt" light is solid red, then the sensor is calculating the salt to be below 2,600 and it will turn the cell off. If the "Cell" light is flashing, or off, then the cell is off.

The "Cell" light should flash if the cell needs cleaning. It wouldn't hurt to check it anyway. What are all of your chemical levels? If your water chemistry suggests scaling is possible, then you have to be extra vigilant about checking the cell. If your filter pressure is unusually high, that could also suggest scaling. The cell has a reversing polarity to help keep the cell clean.

The diagnostic wand I referred to is helpful because it allows you to know exactly what the system thinks the salt is.

Also, note that salt reading are not very accurate. It is not unusual to be several hundred ppm off with any test. You could triple check the level by taking a sample to a pool store that has a salt meter (hopefully properly calibrated), but that's not really necessary.
 
JamesW said:
If the "Low Salt" light is flashing red, then the sensor is calculating the salt to be between 2,600 and 2,800 ppm and it wants you to add salt, but it should continue to work. If the Cell light is solid green, then it is working.

If the "Low Salt" light is solid red, then the sensor is calculating the salt to be below 2,600 and it will turn the cell off. If the "Cell" light is flashing, or off, then the cell is off.
Click to expand...

James - This is part of my concern. the Low Salt light is solid red and the Cell light is solid green and producing chlorine. My salt level is a minimum of 3570 (test strip) to a maximum of 4000 (drop test). I can understand that the unit thinks the salt is somewhat low due to the reduced water temperature but if the system is sensing that the salt level is 2600 ppm (970 to 1400 ppm lower than it actually is) and yet still producing chlorine, I think something is amiss.

bk406 - I understand that the water getting colder affects the system's ability to properly sense the correct salt level, but it's way above the 52 deg. that the mfgr. says is the cut-off point where the low salt light comes on, and due to the above discrepancy in actual salt readings and what the system is telling me (salt at or below 2600, turning on the red Low Salt light) I suspect there may be something to be concerned about, especially since the problem did not occur last winter with similar and even colder water temps.

As a first step I'll go ahead and clean the blades in an acid solution and see what difference, if any, that makes.

Any other suggestions welcome.

Gary
 
It does sound like something is off. It could be the temperature or salt sensor.

If this is a new unit, then it might be under warranty. If the dealer won't help, then Pentair might be able to help. You can contact them at their website or on their help forum at http://poolfyi.com/forum

Here is a similar problem.

Also, some pool stores have a test bench set up to check and diagnose cells.

You could try cleaning the cell. Turn off power to the unit, clean the cell, reinstall the cell and then power back on. Cycling the power will make the unit recheck the salt level.

I see that you have a variable speed pump; what speed are you running the pump at?
 
The conductivity of water drops with temperature. It's roughly a drop of 2% per ºC temperature drop (the alpha constant is 0.0214). The drop in conductivity going from 85ºF to 64ºF is 1+0.0214*(64-85)*(5/9) = 0.75 so a 25% drop. If there is no temperature compensation in your SWG's reporting of salt level, then this would have 4000 ppm seemingly drop down to 3000 ppm while 3570 ppm would drop down to 2813 ppm. Of course, the actual salt level isn't changing, but the conductivity is.

As James also noted, if the cell develops scaling then the current will drop so this will also show up as if there were a lower salt level.
 

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JamesW said:
I see that you had this problem earlier here. What happened with that?
Click to expand...

JamesW - The earlier problem was different in that the "Cell" light would never come on and hence, no chlorine production. They ended up replacing the unit under warranty. (I'll update the other post - thanks for bringing it to my attention)

However, the problem seems to be solved for the moment, at least. I cleaned the cell this morning with a water blast and acid soak. There was no discernible build-up on the blades and very little bubbling in the acid bath. When I re installed it and powered it back up, within a couple of minutes all lights were solid green. I'm currently running the pump at 1650 rpm with a 2 hr. cleaning cycle at 2200 rpm. I'll see what the lights look like at the end of the day when I get back from work.

Thanks for all the help and info from everyone.

Gary
 
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