Pentair IC-40 - Incorrect Low Salt Reading

[sjsherratt]

Hello, I have been researching the forums regarding Low Salt level readings on IntelliChlor IC-40 units.

My IC-40 worked fine through early spring, then I performed the acid wash procedure, and now salt level readings are always low: 2250-2350, and the Low Salt LED on the IC-40 is always red.

Leslie's test reported salt level of 3450. A couple of days ago, I added a bag of salt, but the IntelliChlor's reading did not move. Flow LED is green, Cell LED is green. Water temp is 68F. Cell life diag shows 40% (i.e. 4,000 hours). My unit is old. V2.01. Manufacture date in 2009, though this unit has not been in my system that long. It was a warranty replacement by the Pentair rep, likely a refurb unit.

My question is whether replacing the flow sensor is likely to resolve the incorrect Low Salt reading, or should I bite the bullet and replace the whole unit? I know the thermistor in the flow sensor provides a temp compensation input to salt level / conductivity measurement, but the salt sensor isn't part of the flow sensor (i.e. the two nubs behind the flow sensor).

What do you think? Is a $91 replacement sensor a good bet to fix the errant Low Salt problem vs. replacing the IC-40?

Thanks,
Scott

Other chemistry:
Pool Surface" Pebble, 23K gallons
Free Chlorine = 6.1 (I added powder over the winter)
Total Chlorine = 6.21
pH = 7.5
Total Alkalinity = 80
Calcium Hardiness = 595
Cyanuric = 69
Iron = 0.1
Copper = 0
Phosphates = 93

 

[JoyfulNoise]

You can get the cheaper generic version fo the same OEM part on Amazon for half the cost ($50). The thermistor that is potted into the flow switch goes bad very easily and gives a low salt reading. If you're just looking to make a quick fix, don't waste your money on the OEM part as the generic is the exact same thing...they come from the same 3rd party manufacturer.

Also, if the cell has no white/gray scale visible on the plates, then there is no need to acid wash. Acid washing the cell degrades it's useful life.

 

[sjsherratt]

Thanks JoyfulNoise. I see a few on Amazon, some with some reported poor quality. Do you have a link to one you can recommend?

Yes, the plates had calcium that couldn't be removed with a jet from the garden hose...

 

[JoyfulNoise]

Thanks JoyfulNoise. I see a few on Amazon, some with some reported poor quality. Do you have a link to one you can recommend?

Yes, the plates had calcium that couldn't be removed with a jet from the garden hose...

I don't have an exact link...you'll just have to try a seller that has some decent ratings. I don't really trust Amazon reviews much as there is always operator error involved. You just have to make sure the flow switch is compatible with an IC40 which means it has 4 wires - two for the flow switch and two for the thermistor. Some people get the wrong model flow switch and then think it's the sellers fault. And, as is the case, a lot of people don't know what they're doing, install the switch wrong and then blame it on quality.

 

[sjsherratt]

OK. Thanks for the tips!

 

[Jimrahbe]

S,

If your only choice is to replace the flow switch assembly or replace the entire cell, then as a test, you can just cut the green or white wire between the cell and the flow switch. This will remove the thermistor from the circuit. When this happens, the IC40 uses an internal resistor which makes the cell think the water temperature is about 72 77 degrees. It can't make it any worse than it already is.. If this makes your cell work, then installing a new flow switch will do the same thing.

Note... This only applies if you have a flow switch that has four wires.. The Red and Black wires go to the flow switch. The Green and White wires go to the thermistor...

If you cut the wire, then turn off your system, and reboot the cell.. It should do its red/green flashing lights which will re-calibrate the salt reading. Keep in mind that a good reading can have an error +/- of 500 ppm.

Another option, which I stole from one of our experts, is to add a standard 10K water temp probe, and wire it in place of the thermistor inside the flow switch. So far I have this modification installed in two systems and it seems to be working very well.. The external thermistor does not seem to have the same high failure rate that the internal thermistor has.

Thanks,

Jim R.

 

[sjsherratt]

Thanks for the details Jim. Sounds like a good test! I will try it once it stops pouring rain here ;-). -Scott

 

[Collin_Smith]

Jim,
How would I wire the new 10k ohm temp sensor? Directly to the board, or spliced into existing wires? Also, would it matter which wire (from new sensor) terminates with the green/white from existing sensor?
Thank You

 

[Jimrahbe]

Collin,

In this crude schematic, you can see where the thermistor inside the flow switch assembly is cut out of the circuit, and replaced by a standard temp probe that is inserted into the main plumbing..

Please let me know if this does not make sense..





Jim R.

 

[sjsherratt]

Thanks for all of the info. I cut the white wire, restarted, and the reported salt level went from 2250 to 3150. Water temp is down to 63F. 3150 is still a little lower than I expected (though 4 inches of rain could have diluted things since last week), but the Salt LED is green, which is an indicator that it is likely producing chlorine again. I went ahead and ordered the replacement flow sensor, but I like your work-around with the external temperature sensor. The schematic is a great help too! Thanks again. -Scott

 

[JamesW]

With a cut wire, the temperature defaults to 77 degrees, which is still not accurate but closer than before.

Get a Pentair water temperature sensor so that you can do the hack when you get tired of replacing the flow switch.

 

[sjsherratt]

Thanks. I'm "playing by the rules" this time, but will prep to be a hacker next time! At least now this makes sense. I wish the Pentair documentation would provide more details.

 

[sjsherratt]

New flow sensor installed, salt reading now matches Taylor K-1766 results. Thanks all for the guidance. I just ordered some 10K temp sensors so one step closer to being ready for the "hack" next time.

 

[bobhatfield]

I fixed my issue with the above hack - the diagram was very helpful. Warning to future DIYers: the above schematic represents everything at the IC-40 and NOT the transformer box. (There are black/red/green/white wires in the cord leading from the wall box to the IC - take it from me, those are the wrong ones to cut .) To get to the above green and white wires, remove the cover marked "Flow" from the IC-40 (attached image) and cut into the black wire sheathing connecting the IC to the flow switch assembly.

Also, here's a good thread on how to check your water temp using the IC-40 panel and how to read the output from an ohm meter to test your (new hack) temp probe.

pentair ic40 SWG salt level indicator acting up

hi , my salt cell good/bad- green-red, salt level indicator is acting strange. I have adequate salt levels, (i have tested nearly every day at the local pool store and i have gone from 2600 up to 3400 and this indicator continues to show low salt. The only time it wil go to green is for the day...

www.troublefreepool.com

File:10K thermistor chart.png - Further Reading

www.troublefreepool.com

TFPools, and you guys just saved me another $1,000.