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Post by houpla on Sept 5, 2021 20:54:09 GMT 1
Help! Polarengineer? Vic? I had the 'bright' idea of running a 100m black plastic pipe from the pool filter, round the (generous) surround, then a slinky effect, coils for a 20m run, in full sun from 11am, on a gentle slope, then back to the pool. The water gets suitably hot, but the debit is pathetic!
Could you explain, in blonde terms, where I've gone wrong, svp?
The only explanation I can come up with is that I had my usual contretemps with anything remotely long and thin (string, wire, hoses etc) and the coils probably change direction a couple of times. Would this be a factor?
I know the pump is slightly oversized for the volume of the pool, so would it just be a question of altering the ratio of skimmer/heating pipe outflow? Thanks for any light you can shed.....
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Post by hal on Sept 5, 2021 21:11:57 GMT 1
Co-incidentally this - the slow return, not your heater - was a subject in the pool forum of one of the earlier forums.
The thinking now is that you do not need a powerful return. Google it and there are many pages on slowing down ones pump. In your case it will not be saving money, but you are getting something in return. I cannot quite get to grips with the theory and too have an oversize pump just so that I can see the return shooting half way down the pool!
As to your actual problem, I think the only way without a new pump is reduce the resistance you have built up in your heater - corners, pipe length and size etc.
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Post by houpla on Sept 5, 2021 21:26:39 GMT 1
That was one of the questions.....would the 'reverse flow' in a couple of coils provoke an important resistance? And yes, the pipe is connected by 90° connectors at the corners of the surround in order to minimise it's visual impact. Hmmm....think I need to revise the layout a bit.
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Aardvark
Non-gamer
Living in soggy 22 and still wondering what's going on.
Posts: 1,592
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Post by Aardvark on Sept 6, 2021 9:01:26 GMT 1
I maybe don't fully understand your installation but I have read many articles about the practice of using black hose installations to gain "free" heat using natural thermal action to eliminate the need for a pump. A few points: Pipe bore size limits flow as it gets smaller. Tight bends (ie. 90 degrees) will restrict flow rate. Outlet (hot) end needs to be higher than the inlet (cold). Flat spiral configuration laid out on a flat roof is widely used for domestic heating. Insufficient flow can be solved by fitting a solar powered low voltage pump. A very interesting topic that I did a lot of research on when I bought my house. No electricity, etc. and would have been the best time to look at off grid or semi-off grid options. I didn't go anywhere with the idea because it was all way above my budget. Lots of inspirational websites out there. |
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Post by annabellespapa on Sept 6, 2021 12:50:03 GMT 1
I heat my pool with a log burner that is stainless steel and sits in the border behind the pool, it was originally for a wooden hot tub but there wasn't any filtration of the water so it became very expensive to empty and re-fill every couple of days.
This summer our 10,000 litre pool after 8 hours of heating got to 31 degrees, we are in Brittany and during a hot spell matching the 31 degrees I maintained that temperature for nearly seven days with no further heating, using a solar cover when no one was in the pool plus frequent bursts on the filter pump.
The log burner cost £325 and that was 10 years ago and is 28kw, I burn anything I don't dare put on our indoor log burner, so the fuel is practically free. Any log burner set up to heat water/central heating can be used in line with a filter pump and a sand filter.
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Post by pcpa on Sept 6, 2021 13:20:00 GMT 1
Swimming pools have to be heated in summer when the outside temperature is 31°c? 
I have been in a hot tub in the alps in winter heated by a log burner and it was spectacular, after an hour or so you had to dump snow in there to avoid scolding.
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Post by Polarengineer on Sept 6, 2021 13:28:02 GMT 1
To be able to help houpla, please state the size of the pipe, how many bends/elbows involved, data of the pump, head, capacity, power (if you state the make and model with the motor size, I can find out more data). Filter outlet pressure when skimmer is set to minimum functional flow. Height difference between the pool level and the heating pipe outlet.
note that if any rise in height of the pipe is countered by an equal fall in height then these can be ignored ( such as a coil(s) laying up an embankment). The only change of direction of concern is in elbows, long bends are not so detremental.
from the problem so far explained, I would assume you have a 25mm PE pipe (any larger is very costly) and possibly less than 1 bar filter discharge.
Is the current setup giving a good heat? More flow will reduce this.
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Post by houpla on Sept 6, 2021 13:34:25 GMT 1
Just to clarify...the actual heating part works like a charm...the water's around 60°C when it dribbles out of the pipe into the pool. I wonder if you've hit the nail on the head, Aardvark? The pipe runs on the flat around the pool, then descends slightly where the coils start, slinkying up again to the original level, then on the flat back to the pool. So at no point is the pipe higher than the pump outlet. The other factor might be that OH tapped into the pump outlet pipe without in any way, shape or form calculating pressure and flow rates. I strongly suspect that he has as much idea about all that as I do (n't)  He insists that a dribble is all to the good as it allows the water to attain a higher temperature. Bof! The net result is that even running the pump 18 hours a day, the hot water entering isn't sufficient to make much difference. So once the 'kinks' are sorted out to reduce resistance, the only other solution would be to increase the size of the pump outlet and possibly the hose connecting that to the black plastic pipe. Just as an aside, the 'system' was pretty cheap. About €30 for the pipe, and same again for the connectors. |
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Post by annabellespapa on Sept 6, 2021 14:03:37 GMT 1
Swimming pools have to be heated in summer when the outside temperature is 31°c? I have been in a hot tub in the alps in winter heated by a log burner and it was spectacular, after an hour or so you had to dump snow in there to avoid scolding.
You obviously haven’t met my wife and daughter, having emptied the pool that the winter cover had decomposed into, jet washed the green walls and base and re-filled and treated, the next criteria from them was that it had to be above 28 degrees, to justify all the work I had done for a pool that hadn’t been touched for over a year, it was the only way it would of been used. 😂 |
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Post by hal on Sept 6, 2021 14:08:42 GMT 1
Go back to an earlier post of mine. All might not be lost. It depends on what your 'dribble' actually is.
Do you have any way of measuring the dribble in M3, and do you know the M3 of the pool?
The concensus (google) is (I say this in case an expert comes in and trashes my answer before it all descends into chaos as on the previous forums...) that as a minimum, a domestic pool should be turned over once a day and preferably a little more. It could be that your dribble over 24 hours might be enough. OK, so you will have to run your pump 24 hours, but this is the price you might have to pay to get heat. Remember the school physics: You will not get something for nothing.
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Post by houpla on Sept 6, 2021 15:15:59 GMT 1
Swimming pools have to be heated in summer when the outside temperature is 31°c?
I have been in a hot tub in the alps in winter heated by a log burner and it was spectacular, after an hour or so you had to dump snow in there to avoid scolding.
Normally, at least in July, August and September, the nights are warm enough to keep the pool water within acceptable limits, say 22°C - 26°C. That certainly hasn't been the case this year. Incredible drops in overnight temps, causing havoc for growers in the region. |
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Post by pcpa on Sept 6, 2021 15:58:17 GMT 1
What do they grow in their swimming pools, weed? |
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Post by landmannnn on Sept 6, 2021 16:17:28 GMT 1
Roughly speaking..
A pool hose has a diameter of 25mm, so an area of 450 sq mm.
A garden hose at 10mm has an area of 75sq mm.
So to allow the pump to maintain its flow rate, you will need to run 4 to 6 garden hoses in parallel using some kind of manifold.
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Post by houpla on Sept 6, 2021 17:12:08 GMT 1
To be able to help houpla, please state the size of the pipe, how many bends/elbows involved, data of the pump, head, capacity, power (if you state the make and model with the motor size, I can find out more data). Filter outlet pressure when skimmer is set to minimum functional flow. Height difference between the pool level and the heating pipe outlet. note that if any rise in height of the pipe is countered by an equal fall in height then these can be ignored ( such as a coil(s) laying up an embankment). The only change of direction of concern is in elbows, long bends are not so detremental. from the problem so far explained, I would assume you have a 25mm PE pipe (any larger is very costly) and possibly less than 1 bar filter discharge. Is the current setup giving a good heat? More flow will reduce this. Hello PE! Here goes...4m of 15mm hose connected to 100m of 25mm PE. 4 x 90° elbows. The pump is a Hayward 1.5cv triphasé with S0246S sand filter. 14cm3, does that sound right? Pool 12 x 5 . 88m3 Height difference 150mm to water surface level. Filter outlet pressure....now would this be indicated by the pressure gauge between the pump and filter? Dial reads little hand on 10, big hand on 20 That's as technical as it gets chez les blondes  Thing is, I don't know whether it's set on minimum functional flow. I'll try to persuade OH to dig out his notes and look in on the forum, so he can perhaps provide better details. Many thanks for taking the time to reply! ETA debit from the heating pipe is 5l per 2.83 recurring minutes. |
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Post by stevefrance64 on Sept 6, 2021 22:50:37 GMT 1
"note that if any rise in height of the pipe is countered by an equal fall in height then these can be ignored ( such as a coil(s) laying up an embankment)." but only if you are sure there are no air locks best check to see if it will syphon on its own that's to say get the outlet lower than the inlet and see if you have a constant flow
It could be interesting to see what flow you have at a lower outlet if you bye passed the pump, it could be a long hard suck
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He insists that a dribble is all to the good as it allows the water to attain a higher temperature. Bof! The net result is that even running the pump 18 hours a day, the hot water entering isn't sufficient to make much difference. So once the 'kinks' are sorted out to reduce resistance, the only other solution would be to increase the size of the pump outlet and possibly the hose connecting that to the black plastic pipe.