FC Demand.

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PoolStored

PoolStored

TFP Expert
Gold Supporter
TFP Guide
Jun 24, 2021
15,880
Ashtabula, OH
Pool Size
29000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60 Plus
I had a thread last month with an unexplained FC loss...like low salt caused the cell to stop working. Added salt and I was in business. Now I can't lose FC to save my soul. 10-15% was working great. This week, still sunny and consistent weather, but FC was rising with cell at 5%. Tested this morning FC 10. SWCG OFF all day. FC 10 tonight...

So I got the thinking cap on...and asked myself...Self, what is the actual sun pattern in Ashtabula seasonally...i.e. "September 1 is like what date for sunrise/sun set." Solstices are Dec 21 and June 20 (IIRC)...so we are 2 mo 10 days after summer solstice. Winter solstice is Dec 20, + 2 mos, 10 days is March 1. Didn't quite get it right WRT sun pattern X number of days after solstice, but was on the right track. Looking up sun pattern for Ashtabula...September 1 is like April 10 give or take (red line comparing sundown)

1693627307780.png


Another look at comparing sunrise, somewhere around April 10 is like September 1.
1693628091788.png

OK, FC demand in April is low. I went back and looked at logs last year...I was at SWCG 5% by 9/1...I just didn't remember that...OK, so SWCG output of 0-5% it is in late August/Early September in NE Ohio for me!

@JamesW Why does the sun pattern for Dawn and Dusk not match up with the number of days past solstice? Said another way, I would expect September 1 to look like March 1 from a sunrise and sunset perspective...why the discrepancy?
 
September 1 is still falling from long days to even at the equinox solstice, so it's longer day than night. September 1 is a longer day than September 21.

March 1 is on the opposite side of the equinox solstice, with daylength rising toward even. That is, March 1 has less day time than March 21.

September 1 roughly matches April 10 (both ~20 days inside the period of days longer than nights)
 
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Days around winter solstice are short, days around summer solstice are long. Therefore at same periods after winter / summer solstice you don't have same day lengths (unless you are looking at exactly 1/4 year after the solstices which would be the equinoxes).

You need to look at symmetrical periods before and after a solstice for same daylight hours.

September 1st is something like 72 days after the summer solstice and April 10th something like 72 days before the summer solstice, therefore those days are comparable in sunshine hours and sun angle.
 
So thinking about this more, the equinox notion makes sense. But why is it a non-linear function? Did more searching and come to find out, daylight is Sinusoidal because of the tilt of the axis and the elliptical orbit causes the path to be faster as the Earth approaches the sun and slower as it moves away. I never knew that. It is also the source/inspiration for the Yin Yang. 😲 #alwayslearning
 
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The earth orbits the sun due to the curvature of Space-Time.

For all objects going below the speed of light, the curvature of time is the most important factor.

So, the time on earth is affected by the velocity of the earth causing relativistic time dilation (Time slows down) and relativistic time dilation due to the curvature of time.
 
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The sin curve also explains why around the solstices your FC demand is pretty constant for a while. That's when the sin function is around the maximum (or the minimum) where the rate of change is pretty slow (around the max and min of the curve you can approximate the curve with a horizontal line).

Whereas around the equinoxes, the rate of change of the sin curve is at it's fastest (the curve is at it's steepest), you can approximate the sin curve in this period with a 45° line. That's why you have to keep adjusting your SWG in the weeks around September 21st and March 21st more frequently than around June 21st and December 21st.
 
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mgtfp said:
That's why you have to keep adjusting your SWG in the weeks around September 21st and March 21st more frequently than around June 21st and December 21st.
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It seems to me that the SGW makers should program this into their software so that we do not need to keep doing all of this adjustment.

Also, the total solar eclipse on April 8, 2024 will reduce the SGW requirements for those in the path as the moon blocks the sun from shining on the pool.
 
JamesW said:
Also, the total solar eclipse on April 8, 2024 will reduce the SGW requirements for those in the path as the moon blocks the sun from shining on the pool.
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Are you saying we have to upgrade the TFP Servers to prepare for a spike in panicked questions about sudden occurrences of dangerously high FC levels in the aftermath of the eclipse?
 
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dfwnoob said:
Everyone knows the earth is vaguely in the shape of a flattened orange and it's supported atop a tortoise, so this is all nonsense.
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This one here is one of my favourites about mythological vs scientific world views:

 
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I'm feeling sad because my sundial rusted through, irretrievable. It had a little man with a fishing rod sitting on a dock, and a small pond around him. Cast iron. The little man's fishing pole served faithfully as the gnomon for decades. Chucked it in the red bin. Vale friend 🫡
 
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