PoolPilot Digital CyA levels

[smallpooldad]

PoolPilot states that if you want to use the digital section to control pH the CyA has to be kept at between 30 and 50 ppm. If you want to keep the CyA in the 70 to 80 range it cannot be used.

Assuming a target Chlorine level of 8 (yellow algae/mustard gas issues in our area), the Power Level was just moved to 3 and at 82F it is running at 70% to acheive this level over a 5 hour period. This seems to be the minimum hours to acheive a Chlorine level of 8 without much fluctuation.

It was at Level 2 at around 93% to 97% but PoolPilot states it would be better for the SC60 cell to run it at a higher level (Level 3) and a percentage no higher than 75%. If the CyA was lowered to 50 it might be possible to acheive a Chlorine reading of 8 ppm, but then the pump would need to run for longer. As the KwH is around 35 cents in Honolulu it would start to get very expensive. At present in 5 hours it compensates for around a 3 ppm daily loss of chlorine.

The digital section is presently turned off and it doses a constant 2-3 oz of acid daily, adjusted back and forward every 4 days.

If the CYA level was at 50 ppm then would it be correct to assume the pump hours would have to increased considerably?

A second question for interest's sake, what is the daily loss percentage of Chlorine at a CyA of at 50 ppm and the loss at say 80 ppm?

The reason the CyA is kept in the 70 to 80 range is that it seems to cut down on acid usage considerably and the alkalinity stays at a constant 90, it never seems to move, I do not know why. When the CyA was kept at 35 both the usage of acid to control the pH and baking soda to control the alkalinity were very high. I suppose one "Cannot Have The Cake And Eat It To" at least in this case, with our soft Hawaiian water, whose pH is around 8.2 out of the tap.

Presumably areas with more acidic water might not have these issues.

 

[JasonLion]

You can use the PH controller without the ORP controller and as long as you are not using the ORP sensor, the system doesn't care what the CYA level is. For an outdoor pool you are far better off leaving the ORP controller turned off, leaving CYA around 70 to 80, and sticking with percentage control. The system is far more reliable that way, will last longer, and costs less to operate.

I can't imagine that there is any reason to keep FC at 8 with CYA around 70-80, a minimum of 5 should be more than enough.

Very roughly speaking, chlorine consumption is about double with CYA at 40-50 instead of 70-80.

There is no reason to raise TA as high as 90. If it wants to stay there, then fine. But the PH will be much more stable at lower TA levels (down to 60).

What you are saying about power levels and percentages is true. You want to run at the power level that gets you closest to 50%.

 

[smallpooldad]

Jason Lion,

Thank you for the quick response.

I do not use the ORP controller but thanks for letting me know that that is the issue, I should have paid more attention to the manual. The TA just sticks at 90 both in my pool and my neighbour's maybe it is just our water. And yes the pH does float upwards by about 1 - 2 ppm per day depending on the day.

The reason I maintain 8 ppm of Chlorine is that I take the CYA/Chlorine chart's Yellow Algae/Mustard Gas number for a CyA of 80 and adjust to 60% of the recommended number for a non-SWG pool. Yellow Algae and Mustard Gas is for some unknown reason an issue in our part of Honolulu.

I would like to run the pool longer setting the SWG to a 50% output but my wife would kill me if she saw the electric bill go any higher than it already is.

Thank you for your help it is much appreciated.

 

[JasonLion]

You aren't making very much sense. There is no reason to run at 8 ppm of chlorine. If you don't have mustard algae then it is too much and if you do have mustard algae it isn't even remotely enough. I can't follow whatever you were trying to explain.

There is no reason to run the unit at 50%. The 50% rule is only about picking a power level. Once you have picked a power level and a pump run time, you then run the SWG at whatever % it takes to achieve the FC level you are targeting.