My TurboCell940-CUL doesn't seem to make FC as well as my old T15. Box too old?

Jul 12, 2011
48
London, ON, Canada
Search turned up empty. My old T-15 cell died last year after 7+ years (Summer operation only, pump timer on ~1/3 time, chlorinator set to ~50%)
I replaced it with a Hayward TurboCell940-CUL extended life cell, which I understood was the same as a T-15, just supposed to last longer. I bought it last year but never installed it since the old T-15 was barely holding on so I planned to start fresh this year. There was a note on the 940 cord about the importance of setting the Hayward controller Box to the settings for for the 940, but my controller box is old, firmware version 1.4, so it doesn't seem to have any way to change the settings for different cells. I thought I read last year that it didn't matter with the old boxes. The cell reads a NaCl level of 3000 on the controller box, agreeing with an external salt reading.

When generating, it reads 24.9 volts, 4.73 A, so it should be generating FC well. However, I can't get my FC over 3 with 100% generation, even though I always used to use only 35-70% generation setting and run the pool around 4-5. Everything else is in the normal range. TA ~80, Ca~350, pH 7.8. Stabilizer normal too.

The other thing is this: I used to check the chorinator by comparing water returning to the pool to the regular pool water & finding the FC level about 2-3 higher than the pool. Now I find the FC level 0.5-1 higher than the pool sample. It just doesn't seem to be generating as well as the old T-15.

I should add that the water looks great and CC is 0. The only other thing is that I replaced my 15 year old main pump - although it's still a 3/4 HP, the new one seems to flow ~45-50 GPM on my flow gage, vs. the 40 GPM of my old pump.

Thanks for any insight. I'm concerned when we get the warmer weather my chlorinator won't be able to keep up or that I may have some sort of counterfeit cell? I bought it from a discount pool place (and can't find the receipt!!! Argh!!!)
 
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I would suggest doing an OCLT. You do not say what your CYA level is but taking the FC to 10 ppm with liquid chlorine for the OCLT is fine for whatever your CYA level is.
 
Typo in my original post. CC is 0, FC is 3. CYA 40
OCLT done. I brought up FC to 9.0 with liquid chlorine. System off overnight and FC still 9.0 the next morning, so no organic loss.
I still can't understand how I can have current of 4.73 A without getting a much higher FC level on the water returning to my pool.
 
Move the switch from auto to off and check all of the readings.

Move the switch back to auto and recheck the readings.

Move the switch to off for a minute and then back to auto and recheck the readings.

Report all readings.
 
Thanks for the interest guys - much appreciated. Here are the answers to questions:
Board Serial #: 5A0510, Cel #: 5E19309-202546. I read the recommended page - spectacular! I believe that's what I used to replace my thermister a few years ago. My board won't display the cell type or product name, because the firmware at 1.4 is too old.
Board says salinity 3100, which agrees with a AquaChek Salt level dip strip and seems to agree with my pool store's reading.
Move the switch from auto to off and check all of the readings.
OFF: 3100, 61 deg, 31.3 V, 0.00 A, 76%, -0, AL-2, r 1.40
Move the switch back to auto and recheck the readings. (after waiting about 10 s for generation to start, "click")
AUTO: 3100, 61 deg, 24.9 V, 4.57 A, 76%, -3100, AL-2, r 1.40
Move the switch to off for a minute (5 probably) and then back to auto and recheck the readings.
AUTO: 3100, 62 deg, 24.9 V, 4.52 A, 76%, -3100, AL-2, r 1.40
I had just started it in the morning so I think the filter was full of colder water (60-61 deg) so that's the reason for the earlier 61 degrees.

Report all readings.
Flow 48 GPM, pH 7.8, FC 3.5, CC 0, TA 90, Ca 150, CYA 40, OCLT loss 0 (then left chlorinator off for a day to drop back down again)
Water returning through jets FC 5.0
Here are pictures of my circuit board. As you can see, I replaced the faulty thermistor about 5 years ago. I used alligator clips to make it easy if I had to change it again:

Here are pictures of my cel showing the TCELL940-CUL label:

Here are some ducks I'd like to blame the problem on but probably can't since they haven't been back the last few days:

So I'm wondering if my new pump is just pumping more water, so the difference in FC from the pool to the return water is lower than it used to be with my old T-15, since I put in a 20-year newer pump as well. Need more CYA?

Thanks in advance for letting me know your thoughts.
 
Ok. Everything looks good.

At or below 60 degrees, the percentage is reduced even though it's not indicated on the display.

Above 60 degrees, it should be good.

Do an OCLT to see if a SLAM is indicated.
 
Yeah, you are hovering around 60 Deg.. I see you have a heater. Try warming your water up a bit and see if the production bumps up.
Water temp < 50 deg Cell production is off
Water temp between 50 - 60 deg Cell production is set to 20% or less
I found on my SWG, if I warmed the water up to 65F or so that was high enough over the threshold to get out of the 20% range.

Per the TFP Wiki
 

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OCLT test shows no loss of chlorine, as noted above, CC also 0. Water is crystal clear. Looks like I'm on the way once the water warms up a bit. Just need to change a few (presumably) broken laterals in my sand filter and find the leak around my light... This is a busy spring!

Thanks for the help guys!
 
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