I have a Zodiac LM3-24 that is about 4 years old on a 19000 gallon pool. When I opened my pool this spring, I got the pH to about 7.6, got the TA up to about 90 and the salt at around 4800ppm with ph around 7.6. I am very low on CYA (or none at all). Temp of the water about 68F with outside temps in the high 70's low 80's. When I took the cover off, there was no signs of algae.
I shocked the pool with liquid bleach per the pool calculator with FC up around 10 ppm. However, by the next day the FC was down to about 1 ppm or lower. The SWG ran 24 hours the first day and about 8 hours per day there after. the SWG has never gotten the FC back above 1 ppm since opening (3 days ago). The water is clear and I can see the bottom of the pool clearly. But I suspect it is a matter of time before algae takes over.
Looking at the LM3-24 cell, I can see the bubbles coming out of the cell, and the control panel lets me adjust the output. Control panel lights are all normal. I can see a difference in the bubbles on the SuperChlorinate setting verses 1 output bar setting (lowest setting). But even on super chlorinate, it does not keep up. I cleaned the cell in 10% acid although it had no buildup. Using the LM3 troubleshooting manual, I have electrically tested the transformer and all tested correct. I also checked the output voltages on the various output levels going to the cell. All seem to be normal. I don't know how to test the actual SWG Cell to confirm all plates are functioning normally. Could a few plates be "dead" and it cannot output enough chlorine now (ie only partially working)?
Only strange thing is on the inside of the control cabinet and on the back of the LM3 Control PCB(ie the control panel PCB), there is a blinking red LED. I cannot find any reference in the LM3 manuals about this LED so I don't know if that means something
But reading the Pool School and the "how to shock your pool", could the problem be that I simply have not shocked the pool enough and combined with the low CYA, the chlorine dissapates faster than the SWG cell can keep up?
All advise appreciated and I am eager to learn from the pros. I certainly am stumped.
I shocked the pool with liquid bleach per the pool calculator with FC up around 10 ppm. However, by the next day the FC was down to about 1 ppm or lower. The SWG ran 24 hours the first day and about 8 hours per day there after. the SWG has never gotten the FC back above 1 ppm since opening (3 days ago). The water is clear and I can see the bottom of the pool clearly. But I suspect it is a matter of time before algae takes over.
Looking at the LM3-24 cell, I can see the bubbles coming out of the cell, and the control panel lets me adjust the output. Control panel lights are all normal. I can see a difference in the bubbles on the SuperChlorinate setting verses 1 output bar setting (lowest setting). But even on super chlorinate, it does not keep up. I cleaned the cell in 10% acid although it had no buildup. Using the LM3 troubleshooting manual, I have electrically tested the transformer and all tested correct. I also checked the output voltages on the various output levels going to the cell. All seem to be normal. I don't know how to test the actual SWG Cell to confirm all plates are functioning normally. Could a few plates be "dead" and it cannot output enough chlorine now (ie only partially working)?
Only strange thing is on the inside of the control cabinet and on the back of the LM3 Control PCB(ie the control panel PCB), there is a blinking red LED. I cannot find any reference in the LM3 manuals about this LED so I don't know if that means something
But reading the Pool School and the "how to shock your pool", could the problem be that I simply have not shocked the pool enough and combined with the low CYA, the chlorine dissapates faster than the SWG cell can keep up?
All advise appreciated and I am eager to learn from the pros. I certainly am stumped.
I did just what you all advised, brought the CYA up to recommended level and then shocked again with bleach. The SWG has kept up ever since. Crystal clear water and pH is maintained right at 7.6. Although I shocked it before, I guess I had something that was eating up the Cl so fast and with no CYA, between the sun and the organics, the SWG did not have a chance. We are getting dumped on with pollen and all the spring time stuff right now so that might have been it. 
