I've had this setup ever since my pool was built in March 2007. Last summer, everything worked flawlessly. I ran my pump about 12 hrs per day and had the Intellichlor set to around 15-18 percent. My chlorine levels were consistently in the 4-7 ppm range, depending on swimmer load.
This summer I have had persistent problems with maintaining chlorine. I check about 2-3 times per week, and several times that FC has been below 1.0 ppm. Whenever this happened, I superchlorinated the pool and increased the IC40 running percentage. Throughout all this, the water remained clear. Also, all the LED's were indicating proper operation.
The last month or so, I've seen readings of 0 ppm. Superchlorinating for 24 hours seemed to barely raise the FC levels. At one point, I poured 3 gallons of 10% bleach into the pool AND superchlorinated for 24 hours. I was concerned that I was on the verge of an algae bloom, so I also used an algaecide treatment. The FC was elevated for 3-4 days, and then gradually dropped to near zero again. During this period, I bumped up the IC40 to 40% operation. I'm now at a 60% run rate and still unable to maintain FC. Finally, I set the IC40 to superchlorinate for 72 hours, since I was out of chlorine. It seemed to be working (bubbles coming from the pool returns) for a couple of hours, but when I checked the next day, there were no more bubbles.
So, I checked the diagnostics on the IC40. All the LED's were dim and the "Clean Cell" LED was flashing. I opened up the cell but was unable to observe any visible scale. I didn't have any muriatic acid, so I just reinstalled the cell.
Last night, I noticed that the "Clean Cell" LED had stopped flashing. But then, a couple of hours later it was flashing again.
Does anyone know of issues with the "Clean Cell" feature on these units? The LED came on once before in May as I was about to start up the pool for the summer, and I de-scaled the cell according to the instructions in the Pentair manual. I did not see any scaling then, and there was no bubbling as I was expecting. I am suspecting that there may be an intermittent fault somewhere that is keeping the unit from operating properly.
I went to buy some acid today, so I will try descaling again tonight.
FWIW, I've had persistent issues with rising pH ever since the pool was built. I go through about 3-4 gallons of 31% muriatic acid a month during the summer. I try to keep the pH around 7.5-7.6, but it often rises to about 8.0 due to the chlorinator. I've also got fairly hard water in my area. I believe the calcium hardness of the fill water is in the 250ppm range. During the winter I had my pool water checked at a pool store and they measured CH at approximately 1000ppm using a drop based titration test. At that point I did a partial drain and fill and brought the CH down to approximately 500 ppm. That was in February or so. I imagine that after a hot summer, the CH has climbed again significantly. Could the high CH affect the IC40 cell? If it matters, my salt level, as measured by the IC40/Easytouch is about 3900 ppm. The TA varies as I can't seem to get consistent readings with my AquaChek TruTest reader.
If anyone has any insight on this, I'd appreciate some help.