Pentair IC-40 IC40 Low Salt Readings

[FLHOKIE]

My IC40 seems to be reading salt level at least 600 ppm low. The low salt light was red so it was not producing chlorine. I added salt to the pool because the reading I got was 2150. After 48 hours and 60 pounds of salt, I didn't get much of a change so I inspected the cell and it had a tiny bit of residue on the end of one of the plates. I cleaned it with and acid wash and it bubbled only for a few seconds. I waited a few more and removed the acid. That was yesterday. Today I rinsed the plates with a hose. However, it is reading 2900 ppm. My Hayward analyzer is reading 3500 ppm. The local pool store got a reading of 4250 ppm. I have ordered some of the overpriced calibration solution to recalibrate my salt analyzer.

The low salt is green now (OK) but I think the salt reading is way low.

The IC40 manual shows that it is supposed to be self-cleaning. There are levels of 2, 3, 4, and 5 hours for self-cleaning. It was on 2 and I set it to 5 hours temporarily to see if that fixes the problem. I am not sure over what period of time the cleaning takes place (e.g. 5 hours cleaning per xx hour cycle.)

Has anyone experienced this problem or have any suggestions.

 

[JasonLion]

There are three common causes for lower than actual salt readings: calcium scaling on the cell plates, cold water (typically below 60 degrees causes problems), and an older cell that is about to wear out. If you think that any of those situations might apply you should not add any more salt.

Most SWG self clean by switching polarity every few hours. One plate is always accumulating calcium (perhaps exceedingly slowly, perhaps quickly depending on water chemistry) and the other plate is shedding calcium. The more often you switch polarity the more sure you are to keep the cell clean, and the shorter the cell lifetime (though not dramatically). So cleaning is really happening continuously. If the water chemistry is too extreme, so that CH accumulates very quickly, the unit won't be able to shed all of it.

The correct solution to calcium scaling is to adjust your water chemistry to minimize scaling, as recommended in Pool School.

From your description, you are only having very minor scaling problems, unlikely to be enough to cause the salt reading issue.

 

[FLHOKIE]

Update: The problem was a faulty flow and temperature switch. (part number 520736). I bought the part for about $75 online and replaced it in about a half hour. It was just a matter of removing the cover and unscrewing the faulty switch and screwing in the new switch. I connected the four wires and replaced the cover. It was very easy. A new cell would have cost over $500 so I saved a bundle! The cell was in great shape except for the switch which failed in a little more than a year.

 

[bigdav160]

Ahh, another thread that runs contrary to my own experience.

Glad it fixed your problem but keep an eye on it.