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[url=http://www.troublefreepool.com/bernoulli-vs-the-pool-guy-t26694.html#p220462]This post[/url] and [url=http://www.troublefreepool.com/bernoulli-vs-the-pool-guy-t26694-60.html#p221533]this post[/url] detail the main piping head losses in the system BEFORE I got a variable speed pump.  The solar added 150 feet of round-trip 2" pipe to and from the starting point on the roof which is one story but pitched.  The solar goes the entire length of the roof with zig-zag roof hips and probably at least 120 feet round-trip of again 2" pipe.  The head loss from the panels at 2 feet of head is almost negligible compared to the overall system losses mostly from the very long pipe runs.  The piping for the solar is over half the total loss.

With a separate panel system, either glazed panels or evacuated tubes, the circulation through the panels can be at a relatively slower flow rate since the water getting hotter is not a problem for these panels and therefore results in a very low pump electricity cost for that part of the system.  So one can locate the heat exchanger closer to the pool pump circulation system and of course one can use larger piping for more efficiency as well.  The main pool pump circulation system could then operate at a lower flow rate for additional savings.  One may still need periodic higher flow rates for decent skimmer action, but that's about it.

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  • 5 months later...
I'm looking to install a 10x5m pool in time for next summer and still umming and ahhing over how to heat it.

We have a 40Kw log gasification boiler with 2000l reservoir containing a solar coil but I really don't want to be burning wood throughout the summer especially as I have to cut it down and transport it in the first place...

As part of our roof renovations, we will be creating a south facing roof of about 16m2 which I was hoping to completely cover with evacuated solar panels. The first criteria for them is that they take care of our DHW outside the winter months and maybe help with the UFH in the shoulder months but is it overly optimistic that they could also contribute to heating the pool a touch?

We are in Saone et Loire near Macon

Thanks

Andy

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HI Andy

What you are asking is feasible but there are a a few problems to be solved in the design of your Solar thermal multi system.

The Solar Systems which are design for this configuration combining DHW space heating in winter and pool heating in summer usually have special acid proof coils already installed in the accumualtor to transfer heat to the pool water. I gather that you don't have one so it's going to have to be done another way which is a pity because the internal Heat exchanger is very efficient compared to an external one.

There are a number of installers I know who have a good deal of experience with this sort of solar system which is very specialised and not the sort of stuff for a common garden plumber. If you want me to send you their contacts just send me a PM and I'd be happy to oblige.

O

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Hi, thanks for the reply

The accumulator has an internal solar coil as it was always part of the plan to add solar at some point. It is an Akvatherm Avantti in case you know whether or not this has the kind of coil you mention?

I'm definitely interested in installers so will PM you now...do you think it's feasible for 16m2 of panels to make a decent contribution to heating the pool then?

Andy
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Andy

I know the Akvantti very well as I've got one too, Mine is a 2400EK which means that it has a coil (heat exchanger) up high on the left for preheating domestic hot water and another below that close to the bottom which is for accepting the Solar circuit. So yours might have just the bottom coil in which case it would be the 2000E or two coils in the it would be the 2000EK.

Neither of us therefore has the addition of the acid proof coil exchanger for accepting chlorinated unfortunately. But don't despair I know what needs to be done and I've contacted the installer I mentioned who lives in Dept 73, he also has a solar multi-system and will be well able to reproduce that for you. He is in the swimming pool and spa business and so understands what is needed. I'll send you his contact details via PM.

The second question you asked requires the answers to more questions before you can get close to a cogent response.

Firstly,

What will be the pool volume, 10 x 5 x ?, if we can say that its 75m3 then that would be about average.

Next, the insulation on the pool surface matters more than anything else as whatever energy you put into the pool needs to be preserved and not lost to the night sky. So I suggest a floating security cover, which will also comprise your complaint security obligation.

Finally what is the temperature you want and when do you want to start swimming; let’s say that you like it 25°C and you want to swim in May till end of September.

If all of those assumptions are true then 16m2 of evacuated tube solar panel is not enough to get close to that wish list. I suggest that you will need closer to 20m2 (4 x 30 tube panels or more). But your installer is an expert at this and he can advise you better than I can once a site survey has been undertaken (which matters a lot by the way).

Make no mistake; a swimming pool of that size needs a serious amount of energy to raise the temperature even a little bit. The Solar system I discussed is a ‘medium solution’ but not so much that you have a problem to dump lots of heat in high summer when your pool has had enough and there is still more to be had. The real benefit here is that all of the energy is FREE and if, you have a system like you are contemplating which can make use of the energy whenever it occurs throughout the year then it’s absolutely ideal. You will be well set up for the rest of your life.

The purchase of the Akvantti even though it wasn't set up perfectly was the best purchase you have made so far.(well done!)

O

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Hi, thank you for the follow up and the installer details. I'll PM you too with further details but in answer to your questions:

We have a 2000l EK+K tank.

Your pool assumptions are pretty much spot on in that we would hope to achieve 25 degrees+ and use the pool from April/May - September depending on the weather. The pool will be 10x5 with average depth of 1.5m

I would hope to try and insulate the pool as much as possible too. I came across a company called Thermapool when in England recently who made quite big claims about the benefits of insulating the floor and walls properly during construction which obviously makes sense and likewise their insulating cover which heats and insulates the pool although I imagine a separate security cover would be required also.

By my calculations, I think I could squeeze 90 tubes on the south facing roof plus another 30 on the vertical wall it sits on which should be useful in the colder months when the sun is lower.

One question about potentially running under floor heating in the colder months, is there any reason why water can't be sent straight from the panels into the UFH bypassing the accumulator? As the temperatures required are only in the 40 degree range, is it not more efficient to pump it straight into the floor when the panels are operating at lower temps?

Thanks

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[quote user="cruddler"].... We have a 2000l EK+K tank.... Your pool assumptions are pretty much spot on in that we would hope to achieve 25 degrees+ and use the pool from April/May - September depending on the weather. The pool will be 10x5 with average depth of 1.5m I would hope to try and insulate the pool as much as possible too. ......... I think I could squeeze 90 tubes on the south facing roof plus another 30 on the vertical wall it sits on which should be useful in the colder months when the sun is lower. .............One question about potentially running under floor heating in the colder months, is there any reason why water can't be sent straight from the panels into the UFH bypassing the accumulator? As the temperatures required are only in the 40 degree range, is it not more efficient to pump it straight into the floor when the panels are operating at lower temps? Thanks[/quote]

Andy
Interesting questions.

So the accumulator has standard insulation and I assume 2 heat exchanger coils.

Your spec is doable but you are going to have to watch for losses if you want to get good results and you are right to pay attention to the construction of the pool by insulating all sides, surface and the floor, but don't bother with UK firms, there are people here I know who know a lot more about it. In particular about integrating heat from solar or bought fuel and retaining it. These people are at the cutting edge and not stuck in the 1960's like most of the firms here (and in the UK).

You can't use the solar circuit as a distribution circuit on this scale, as there is no controllability. There will also be issues with air pockets and glycol and a lot of other stuff, don't go there, you already have the (nearly?) best 'heat hub' you could possibly have, now you need some who really knows how to make the best use of it to design your system for you.

If you really want to make the best project possible you are aiming for what I call 'ENERGY 'A' rated pool. If that's what you want then its very possible and you'll enjoy the benefits of these decisions for decades to come as you pool costs a pitance to operate when everyone elses becomes so expensive to keep up that they have to choose between rennovations, or filling it in.  To get this advantage, you need to make decisions at this point and to work with specific people who understand what to do, else you'll be amongst the latter group.  More details by email.

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