SWG percentage of filter time

[TishTash]

It appears all SWGs require one to calibrate a percentage of pump run time. How much of the normal variability of the pump running day-to-day (due to swimmer load, water features, pressure or suction cleaners) plays into proper calibration? I'm assuming variable-speed motors have little effect, as I'm imagining chlorine production doesn't vary much with different flow rates.

 

[Newdude]

It varies little if at all. With the SWG providing a constant top off, or at the very least a top off every 12 hours, by the time the FC dips enough due to normal reasons, It’s already being replaced. A huge storm, an incredibly hot day. 25 person party could require a hair extra but those are all relatively rare.

also good guess on the VS pump. The SWG is either on or off and flow/RPms don’t matter providing its enough to activate the unit.

 

[cowboycasey]

You have to run your pump long enough and have enough flow to satisfy your SWG to make chlorine...
The easiest way is to take your CYA to 70, your chlorine to 7 and run your SWG 100% for 6 hours and see where your FC is the next day.. If your fc is low add more hours if it is high lower the hours or turn down your SWG...

 

[TishTash]

If your fc is low add more hours if it is high lower the hours or turn down your SWG...

That brings up another point: Which is preferable (re extending cell life), a cell at 50% for 12 hours or the same cell at 100% for 6 hours?

 

[Dave31410]

That brings up another point: Which his preferable (re extending cell life, a cell at 50% for 12 hours or the same cell at 100% for 6 hours?

It does not matter, although I would prefer 50% over 12 hours.

 

[cowboycasey]

that would use the cell exactly the same but 12 hours would use twice the power to run the pump, I like to run 100% and less pump time...

 

[Newdude]

that would use the cell exactly the same but 12 hours would use twice the power to run the pump, I like to run 100% and less pump time...

Most if us with VS pumps pay so little we don't care. I run 24/7 for an extra $10 month. The water is always moving and sparkly, filtration never stops and chlorine is constantly topped off allowing me to be even lazier.

 

[bmoreswim]

I like more pump run time to keep the our water surface spotless more often. My pump costs about $15/mo. to run for my settings.

 

[Dirk]

If this helps... An SWG does not produce chlorine in a variable way. It doesn't dial down its production of chlorine when you dial it down to 50%. SWGs produce all that they can, all the time they are producing. When you dial down to 50%, it just dials down the amount of TIME the cell produces. So at 100%, the cell will be producing at 100% production for 60 minutes out of every hour of runtime. When dialed down to 50%, the celll will be producing at 100% production for 30 minutes out of every hour. My SWG has an indicator light that glows when the cell is producing, and the light is off when the cell is idle, waiting for its next on cycle.

SWGs will produce chlorine for X amount of hours. At the end of those hours, you buy another one. So it doesn't matter to its lifespan if you run it at 100% for six hours, or 50% for 12 hours. The cell produced for six hours total either way. You'll get the same amount of chlorine in your pool, and you'll wear down the SWG the same. As others pointed out, what runtime matters most to is your pump: more hours = more electricity for the pump and more wear and tear. The SWG doesn't care one way or the other.

 

[TishTash]

... [W]hat runtime matters most to is your pump: more hours = more electricity for the pump and more wear and tear. The SWG doesn't care one way or the other.

True, but a rejoinder and a question:

1) I suppose the advocating of 50% of the SWG over twice the pump time (at half the flow rate) is because power consumption by the pump at that setting is reduced far beyond the proportionate amount, i.e., nearly a tenth of the power required to run a pump half the time at twice the flow rate. So you essentially get the same flow rate (and same chlorine content) at a far lower level of power consumption.

2) Over what time interval does an SWG gauge percentage? For example, if it’s at 50%, does it turn on for 30 seconds per minute? I ask because your example of 30 minutes every hour of a running pump implies one can “sabotage“ that “percentage” by, say, turning off the pump after 30 minutes.

 

[mknauss]

Over what time interval does an SWG gauge percentage?

Depends on the SWCG. Pentair uses a 300 second interval. Hayward uses 180 minutes I believe.

 

[mguzzy]

Yes Marty recalls the same time slices that I do..,,

Personally I set my SWG at 50% and adjust the runtime to match the FC production I need for "normal" conditions. Normal is in quotes because everyone has a different "normal." I did this years ago and really haven't had to change the run time since. I think changing the run time is a bigger hassle than changing the % Cl production which is just a turn of the knob on the controller. Now I can easily adjust the SWG % to match the conditions. More swimmers, hotter weather turn the knob up!, cooling off, decided to throw on the cover: turn the knob down! If you are running 100% on the SWG all the time you will have no wiggle room for adjustment.. that's me, everyone is different.

 

[Dirk]

True, but a rejoinder and a question:

1) I suppose the advocating of 50% of the SWG over twice the pump time (at half the flow rate) is because power consumption by the pump at that setting is reduced far beyond the proportionate amount, i.e., nearly a tenth of the power required to run a pump half the time at twice the flow rate. So you essentially get the same flow rate (and same chlorine content) at a far lower level of power consumption.

2) Over what time interval does an SWG gauge percentage? For example, if it’s at 50%, does it turn on for 30 seconds per minute? I ask because your example of 30 minutes every hour of a running pump implies one can “sabotage“ that “percentage” by, say, turning off the pump after 30 minutes.

1: The energy savings from adjusting flow rate is a separate equation. With a constant flow rate, 50% runtime = ~50% energy consumption. The flow rate (for SWG use) is established by the minimum rate the SWG will require to fire. That flow rate would be the same, whether you're running 6 hours or 12, so if that's all you're considering, the cost is linear. Now if you alter flow rate for other reasons, and for durations other than the SWG runtime, like for skimming or vacuuming or for solar for example, then the math changes, and you're right, increased flow rate costs are not linear.

2: As Marty points out, it varies by model. And yes, you can sabotage the SWG production depending on when you cut off the runtime. You can try to figure all that out, and adjust your schedules accordingly, but it doesn't really matter. You start with runtime X and SWG % Y and see what FC results. Then you adjust either runtime or SWG % to adjust the FC level. The end result is the concern. Now it's good to have a handle on what you're working through, but ultimately it's simpler than you're making it out.

Now, throw in an acid injection system, which uses the same, but different, on-for-x-minutes-per-hour method, and the real fun begins!

 

[mguzzy]

Now, throw in an acid injection system, which uses the same, but different, on-for-x-minutes-per-hour method, and the real fun begins!

Exactly... my acid injection system is I "throw in a cup it in once a week." Its a very analog system and is not prone to power failures or injector clogs.

 

[Dirk]

Something to be said for that, for sure. But my pool needs more acid than that, plus I'm stuck on the following. The great thing about these auto-dosing systems is that they're dispensing all my consumables every hour, all day long. So I no longer have to pour in larger doses to try and stretch the interval between chores. Like when the pool guy was dosing once a week: a few days of harsh water, then a few days of OK, then a few days of bad pH and FC. Now my FC and pH are very stable, virtually 24/7, and that's worth the expense and "adjustment woes" to me...

 

[TishTash]

Depends on the SWCG. Pentair uses a 300 second interval. Hayward uses 180 minutes I believe.

Wow, that’s a pretty substantial range. I suppose it’s a tradeoff between long stretches of nonchlorination and persistently switching the SWG on-and-off over shorter intervals.

 

[poolnoobgrandma]

Yes Marty recalls the same time slices that I do..,,

Personally I set my SWG at 50% and adjust the runtime to match the FC production I need for "normal" conditions. Normal is in quotes because everyone has a different "normal." I did this years ago and really haven't had to change the run time since. I think changing the run time is a bigger hassle than changing the % Cl production which is just a turn of the knob on the controller. Now I can easily adjust the SWG % to match the conditions. More swimmers, hotter weather turn the knob up!, cooling off, decided to throw on the cover: turn the knob down! If you are running 100% on the SWG all the time you will have no wiggle room for adjustment.. that's me, everyone is different.

Agree - with the Hayward automation, MUCH easier to change output percentage than runtime. I have a two speed pump that I run 8 hours on low, 4 hours on high, every day. Current SWCG percentage is 60. I'm slowly dialing that back with shorter, cloudy days.

 

[TishTash]

... You can try to figure all that out, and adjust your schedules accordingly, but it doesn't really matter. You start with runtime X and SWG % Y and see what FC results. Then you adjust either runtime or SWG % to adjust the FC level. The end result is the concern. Now it's good to have a handle on what you're working through, but ultimately it's simpler than you're making it out.

Absolutely correct. I was likewise getting bent-out-of-shape about pH, when honestly it’s been rock-solid through many variables. Which I find mysterious because between aeration and the SWG, I keep hearing about having to add muriatic acid regularly from time-to-time. It may still happen, but it hasn’t yet, so for now I’ll keep whistling past the graveyard.

pH trends

The latest recommendations call for 7.6-7.8 pH, and yet calcium scaling is avoided at lower pH. Given pH’s tend to trend up over time anyway, what’s the downside of keeping things at 7.2-7.5?

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