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Re: solar pool heating

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Posted by on August 6, 2003, 8:45 am
 


accessory

Take the extension rod off of your vac head and submerge the vac head in the
deep end. No need for another stupid "accessory".
All pools above and below ground type suffer from poor water circulation
unless there is a bottom return drain. By keeping the vac head in the deep
end at least once every two days and setting the eyeball return so the water
forms a whirlpool effect, this method solves the water clarity problem,
debris problem, sanitizer inefficiency in the deep end problem, and lastly
temperature stratification. Another benefit is the huge amount of stored
heat versus the old way. Using a solar cover becomes a waste of time.
Mark_



Posted by Nick Pine on August 6, 2003, 2:43 pm
 


Perhaps, in Key West, but solar covers are helpful in most of the rest of
the US. Storing more heat doesn't help if we lose it a lot faster. Why not
learn some physics rather than spreading such misinformation?

Solar covers stop evaporation, and pass some sunlight, unless they are black
(a stupid idea, since water is such a poor conductor for downward heatflow.)

Where I live near Phila, NREL says 1020 Btu/ft^2 of sun falls on level ground
on an average 56.4 F October day, and the humidity ratio w = 0.007, so the
vapor pressure of water in ambient air Pa = 29.921/(0.62198/w+1) = 0.333 "Hg.

At pool temp T (F), with no wind, we might lose Qc = 2(T-56.4) Btu/h-ft^2 by
convection. Bowen's equation says we'd lose Qe = 200(Pw-Pa) by evaporation,
where Pw = e^(17.863-9621/(460+T))... 24h(Qc+Qe)+1020 = 0 makes T = 59.3 F
for an uncovered pool.

With an R1 cover with 80% solar transmission, 0.8x1020 = 24h(T-56.4)1ft^2/R1
makes T = 90.4 F.

Nick


Posted by on August 15, 2003, 8:46 pm
 

benefit

I live in the north east. My in-ground water temp is 88 degrees without a
cover. If you are talking about a cover that retracts effortlessly without
the help of a couple people, then go for it.
The Federal Gov does have some interesting facts about heat loss through
evaporation and why they suggest using a solar cover. They also suggest not
running your pool pump more than 3 hours per day. Laws and actual experience
can be very different.
Thorough water circulation is the best hedge against heat loss unless there
will be a few days without sun.  If the ambient temperature is less than the
pool water that solar cover may end staying on a few days. During that time
bugs and all sorts of stuff accumulate and when the cover is finally rolled
up, that junk falls into the water. Now you have to spend $$ to clean up,
possibly more $$ than what you saved using the cover. If you don't agree,
then you don't own a pool. I mean a REAL pool.
Mark_



Posted by Nick Pine on August 16, 2003, 10:34 am
  

So you don't need a cover when it's sunny and humid...


Bullshit. Storing more heat doesn't help if we lose it a lot faster.
Why not learn some physics rather than spreading such misinformation?

Nick


Posted by Nick Pine on August 23, 2003, 12:19 pm
 

It seems to me that you are, since clean water transmits solar heat well,
so there's little need to mix it to store solar heat effectively (what's
the depth-temp gradiant in your pool with and without your circulator?),
and an uncovered pool has a high heat loss. Storage doesn't change that.

The fact that your pool is toasty in August with lots of sun at 95 F and
50% RH says little about the value of covers or circulation.

Nick


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