Intellichlor good salt level in morning, low salt in afternoon

[karlyc]

Hello!

I have a year old Intellichlor IC40 and the red low salt light has been on for a couple of weeks as the salt levels are testing fine but we haven't been able to get anyone out for service. I started running the pump 24 hours a day a couple of days ago after adding some stabilizer and I noticed that the green light indicating good salt levels was on first thing in the morning when I go out to check things. It switches back to red by the time I'm back out to check things. Any idea what could be causing this? It's so strange and I'm getting tired of dumping chlorine into the pool.

 

[Owner/Builder]

As your pump runs, it turns the salt into chlorine. So now you have low salt, but you have the chlorine you desire. By morning the chlorine has broken back down to salt so your level is normal again. Add more salt so it doesn't get low throughout the day.

 

[karlyc]

Thank you!! I'll give that a try. I might need some new test strips as well, because those are showing 3600 ppm and my IC40 says it only needs 3400 ppm.

 

[drharris]

For the most part, obey what your SWG wants you to do. The IC40 sensor is far from accurate, and it's probably wrong in this case, but it's not yet dead (I bet it will be in another year; those things are flaky - but replaceable). Don't get too caught up in the strips - it's good for knowing the ballpark, but they are very useful so that you don't just blindly dump salt because of a red light and then accidentally go up to 5000ppm! It sounds like your salt level is on the edge of what that unit wants, so just put a bit more in, using strips only to make sure you're not going overboard and fighting a bad sensor.

 

[Jimrahbe]

Karl,

What you are seeing is a pretty common issue with the IC40 style SWCGs. The cell uses a thermistor to help determine the salt level in your pool. Unfortunately this thermistor is less than reliable.

If the cell is under warranty, your Pool Builder will send a Pentair tech out to replace it. If out of warranty you can buy a new "Flow Switch" for about $100 bucks and replace it yourself. The thermistor is part of the flow switch assembly.

There are two wire version for older cells and 4 wire versions for newer cells so you need to make sure you get the right one. You can tell by taking off the white plastic cover where the wire goes into the cell..

The cell only tests for salt twice a day 12 hours apart, so the difference between being good in the morning and bad in the afternoon is just because the water temperature has changed. Even when working perfectly, the tolerance is +/- 500 ppm.

Here is a test that one of our experts provided to test if the thermistor is bad or not...

***
Pressing and holding the “More” button launches the System Status Mode. When the lights finish scrolling, the percent lights indicate hours of usage in 1,000s. For example, if the 40% light lights, that indicates 4,000 hours.

Version 3.1 on adds the ability to determine system temperature. Pressing the “More” button after the display shows 1,000s of hours of usage, will show temperature as follows:

Lights…………….....………Temperature
No LEDs………….…..………Below 30F
40%..........................36 to 45F
40% and 60%............46 to 55F
60%..........................56 to 65F
60% and 80%............66 to 75F
80%.........................76 to 85F
80 and 100%............86 to 95F
100%.......................96 to 99F
100% blinking……..….over 99F
All LEDs blinking……...Sensor bad

The temperature sensor is a 10k thermistor. Its resistance varies based on the temperature. The way it varies is known precisely. So the box measures resistance in ohms and calculates the temperature.

If the thermistor fails in a way that’s obvious to the software, the software will ignore the thermistor and use 75 degrees F as the temperature.

When using 75 as the default temperature, the salinity will be miscalculated by the software for any water temperature other than 75 F.

Thanks for posting,

Jim R.