FC Generation In PoolMath

[revitup]

I’m confused regarding the FC generation displayed in the Poolmath ‘Effects of Adding’ feature. My Hayward system runs in 180 minute cycles. If I run for 1 hour at 30% output, the cell generates chlorine for the first 54 minutes of that 180 minute cycle and stops. PoolMath says that would generate .3 ppm FC.

If I increase my actual run time to 3 hours the cell will not generate any more chlorine because it is still within that 180 minute cycle.

If I increase the run time to 3 hours in PoolMath, the displayed calculated Chlorine production increases to .8 ppm.

Why does Poolmath display an increase in FC production when the cell does not run and is not generating chlorine in those two hours?

 

[jmastron]

I don't think Pool Math attempts to take into account each cell's duty cycle details -- it assumes the output percentage is the actual percentage of the total time.

Incidentally, are you sure the cell generation works like that? The Hayward docs I've found show that a 180 minute cycle time for polarity reversal, but are more confusing as to how the duty cycling of generation itself works. Yes, it could be full on for X minutes at the beginning of each 180 minute cycle and off for the rest, but it could also be using a much shorter cycle for the actual output generation and still fit in the examples they give. Multi-hour generation cycles like the first would definitely introduce weird output like you suggest and be confusing to try to set. Does watching the "Generating" light match either behavior?

I leave my cell at 100% and use a WiFi timer to adjust the output (and it's a Calimar system that doesn't even document the cycle times), but would still be good to know.

 

[ajw22]

You are using PoolMath and your SWG in ways the designers did not anticipate.

PoolMath just does a linear calculation for FC generation based on manufactures chlorine output specifications without considering cycle times or short cycling of the SWG.

 

[revitup]

You are using PoolMath and your SWG in ways the designers did not anticipate.

PoolMath just does a linear calculation for FC generation based on manufactures chlorine output specifications without considering cycle times or short cycling of the SWG.

Sure seems that way. Unfortunately not taking the cycles into account makes for inaccurate results regarding chlorine out put. Seems it would be a pretty simple program correction to take the hours run input, divide by 3 to get cycles, multiply by the % input to get actual cell run time and be able to show the actual chlorine production.

 

[Bperry]

Sure seems that way. Unfortunately not taking the cycles into account makes for inaccurate results regarding chlorine out put. Seems it would be a pretty simple program correction to take the hours run input, divide by 3 to get cycles, multiply by the % input to get actual cell run time and be able to show the actual chlorine production.

Is the assumption all manufacturers have the same cycle? Mine is something like 12 minutes, can’t remember exactly.

 

[ajw22]

Is the assumption all manufacturers have the same cycle? Mine is something like 12 minutes, can’t remember exactly.

It is all over the map. And even varies from version of the firmware. And some times are not known.

SWG Generation Cycle Times - Further Reading

www.troublefreepool.com

 

[mgtfp]

PoolMath would need a lot of extra information, to take the duty cycling properly into account. For example, just entering a runtime of 3 hours doesn't give PoolMath all the required information. It makes a difference wether you run 3 hours in one block, or 3 seperate blocks of 1 hour, depending on the exact duty cycle. PoolMath can only assume that the percentage you enter can actually be achieved by duty cycling within the run time. It doesn't make sense to make PooMath more complex by adding all those extra details.

My SWG doesn't work on duty cycles, but adjusts the cell current. But there still is a small duty cycle effect by its pre- and post flush feature, where it runs the first 5 and the last 2 mins of each programmed period without chlorine production, to ensure proper priming at the beginning and flush out any hydrogen and high pH water at the end.

If I really want to know the exact production percentage, I can look up the previous day's effective percentage in the settings. In my case, the difference to the set point is very small unless I'd run the SWG for a very short period. Maybe your SWG has a similar feature?

You could setup a simple excel sheet to make exact calculations based on your SWG's duty cycling. But I don't think it makes sense to make PoolMath more complicated.

It's similar to PoolMath assuming that the bleach percentage you enter when calculating the effect of adding liquid chlorine is correct. PoolMath doesn't know that the bargain bleach you bought is already two years old...

 

[revitup]

“You could setup a simple excel sheet to make exact calculations based on your SWG's duty cycling. But I don't think it makes sense to make PoolMath more complicated.”
I really don’t see it making poolmath more complicated. I can do the calculation, as you suggested, with a simple excel spreadsheet from a simple manual math calculation, but why should I have to? It’s a computer. It has all the necessary data necessary do the correct calculation to produce a real number instead of a bogus one.

 

[Bperry]

“You could setup a simple excel sheet to make exact calculations based on your SWG's duty cycling. But I don't think it makes sense to make PoolMath more complicated.”
I really don’t see it making poolmath more complicated. I can do the calculation, as you suggested, with a simple excel spreadsheet from a simple manual math calculation, but why should I have to? It’s a computer. It has all the necessary data necessary do the correct calculation to produce a real number instead of a bogus one.

I think the point is that it’s be really time consuming for not much benefit. If ever unit is different and some same units are different with different firmware versions, keeping track of all that and keeping the app updated would be a big hassle.

 

[revitup]

I think the point is that it’s be really time consuming for not much benefit. If ever unit is different and some same units are different with different firmware versions, keeping track of all that and keeping the app updated would be a big hassle.

Poolmath is updated to keep track of every salt cell under the sun. Make and model and rated output. It’s just one more piece of data - cycle time.

 

[mgtfp]

It's not just cycle time. PoolMath needed to know the length of every programmed run time segment and not just the total runtime.

And if it really depends on firmware version, then you really ended up in a mess.

 

[revitup]

Sorry to belabor this but I’d really like to get this straight in my mind.
If I’m understanding what is being said here, if 10 hours pump run time, and 40% output, is input into ‘Effects of Adding’, Poolmath interprets that as the cell is generating chlorine for 40% of 10 hours or 4.0 hours, when it is actually generating chlorine for 4.6 hours?
72 minutes x 3 (3 full cycles) plus 60 minutes (partial cycle)=276 minutes

 

[ajw22]

Sorry to belabor this but I’d really like to get this straight in my mind.
If I’m understanding what is being said here, if 10 hours pump run time, and 40% output, is input into ‘Effects of Adding’, Poolmath interprets that as the cell is generating chlorine for 40% of 10 hours or 4.0 hours, when it is actually generating chlorine for 4.6 hours?
72 minutes x 3 (3 full cycles) plus 60 minutes (partial cycle)=276 minutes

Yes, all of the PoolMath chemical effect calculations are approximations and not perfectly accurate.