Hi,
I've seen a number of 3kw pool heaters on ebay for about =A390. They're for use in large paddling pools up to 15ft in diameter. e.g.:
So I'm wondering if anyone here has had experience of these heaters in this type of pool, and whether its really going to heat a 10ft x 2ft circular pool.
I've got a pool cover too, for what it's worth.
Boz
No experience necessary, just basic physics.
Your pool contains ~ 5m^3 of water, or 5000 litres. This has a mass of
5000kg.A 3kW heater provides 3000J/s.
The specific heat capacity of water is about 4200 J/(kg.K)
So to raise the temperature of your 5000kg by 1 Celcius we need 21MJ. Your 3kW heater would take just under 2 hours to deliver this. So if you're aiming for a 5 Celcius rise, it'd take just under 10 hours.
And this is before you factor in conductive and evaporative losses.
Not that I really approve of dumping large amounts of heat outdoors, but this would be an ideal task for condensing boiler with an extra zone, transfering the heat through a plate exchanger. The temperatures involved will mean the condensing boiler will be operating at peak efficiency (higher even than its published figures for central heating use).
Cost wise, you should compare to running it overnight on cheap rate electricity -- there may not be a lot in it. However, the electricity option is nowhere near as environmentally clean, as electricity generation efficiency is nowhere near as high as even the most inefficient old gas boiler.
The other thing would be to ensure you have a very good pool cover with regards to low thermal losses.
Neither do I. Maybe an option if the OP has the space is a small pump (perhaps a solar powered) and lots of black hose pipe. On a day like today there will be a considerable temperature rise in the water flowing through the hose.
ISTR last year someone building a pool heating system using this technique and been very happy with the results. Google?
The OP could spend =A390 on an electric heater element (!), then pay to run it every day, and not get much rise anyway.
Or the OP could buy =A390 worth of hosepipe, polythene & pump, and get
10kW with 1/10th the run cost of the 3kW heater.Not a tough choice. Cheap pool solar heating is very easy to make btw, probably easier than installing electric into the water.
NT
Pools like that are the easiest thing to heat by solar energy. Just pump the water over a corrugated plastic roof, and back to the pool. an average southish facing car port roof orequivalent should produce several kilowatts.
It may be possible to use a slate or tile roof in a similar way too.
Given enough time it will warm it up a bit, I know someone who ran one continuously on a larger pool for several months last year with the thermostat set to 28deg. The major heating came at the end of the season when they got their electricity bill. The heater isn't on this year.
Also bear in mind that it isn't something you can just plug into an extension lead and forget. Electrical installations near pools are, quite sensibly, governed by quite strict installation rules as the risk of accident is high. Electricity and water don't mix.
Details?
10m^2 collector area, how does it work? Polythene over hosepipe?
ok... firstly I would not use an open roof surface for collection, as a) it will also collect birdshit and other assorted bacteria b) it will leak water onto the roof structure underneath the covering and rot it.
Buy a =A350 pump, checking it can run continuously and has a type of motor that can be slowed down eaily.
Spend the rest of the money on hosepipe, the more the better. Avoid orange, white or light grey. Wind it in a huge flat spiral pancake. You'll get a lot more heat if you space each turn out by one pipe width, but that requires wire or similar to hold it togther/apart. Aim for 10 square metres or more.
Cover the pipe with polythene, add the pump on an RCD, and run it at lowest speed setting.
You now have a fairly efficient low cost 10kW heater.
NT
Ok, many ideas given so far, and I've thought about the cost and environmental aspect and decided not to go for an electric heater.
The pool cover I have is bright blue polythene and gets very hot in the sun.
Would it be best to pull the cover taught over the pool so that it does not touch the surface (i.e. a 6 inch gap between water and cover), or let the cover sag so that it touches the water?
Or, is it better to let sunlight penetrate the water direct and remove the cover during the sunshine?
I A-level physics, and we never covered swimming pool thermodynamics ;-) I got an E anyway, so even if we did I'd probably get it wrong !
Boz
Is the cover just a sheet of polythene or does it have any insulation properties?
If it's just sheet I'd let it sag onto the water during the day so that you transfer as much heat as possible into the water but lift it clear at night so you get the insulation of a layer of air.
Hmm.
10m^2/4cm = 250m. Best price for 30m I can find seems to be about 12 quid. Call it a hundred quids worth of hose. Without the space, it's more like 250 quid. I've wondered in the past about twinwall sheet. If only there was a nice leak-proof way to seal hose to the ends, it'd be ideal. One sheet of clear twinwall on top of one sheet of black.
The design I gave last night is not in fact the design I would use. There are many improvements that would, erm, improve it, including cut cost. I was just too tired to go over em all then.
NT
In article , snipped-for-privacy@yahoo.com writes
I have the 15' version and am looking at the same issue, you can get solar covers for these pools which heat the pool and insulate (its coated bubble wrap by the look of it) BUT this isn't enough to get the water up to a usable temp for the wife but every little helps. I am working on a solution using the central heating perhaps an extra cylinder with the pool water circulated through it or what about turning the whole pool into a giant open cylinder by having a coil of hep2o running around the bottom :-) I will probably end up with a solar solution using black sheets under perspex with water running down them
Look for a solar pool cover:
Something else that could help is to have a shower, gradually turning the water cooler before getting in the pool to acclimatise yourself.
cheers, Pete.
Bubblewrap over the pool when not in use (bubbles down) is both an excellent insulator, and solar collector. Not so good the wrong way up!.
Heh, I have exactly the same issue as you regarding the wife.
Anyway, the ideas seem to be getting too far fetched for me, the average Jo at home, simply wanting to put the pool up for the kids over summer. Solar heating sounds the best, but of course that only works now the weather's perked up. For the last week I've had a pool staying cold in the grey weather!!
Actually, I might dig up the garden and install under-garden heating using a coal-fuelled furnace pumping hot air round sub-terranean chambers. Them Romans wrote the book on environmental heating solutions, surely...
Boz
Is that with solar heating? Even on dull overcast days at this time of year you should be able to get several hundred watts per square metre. Brillant bright sunshine like today and you'll be over a kW/m^2
Be better to burn wood, carbon neutral.
In article , snipped-for-privacy@yahoo.com writes
Another idea... a bank of radiators painted black with water circulating through them, not very pleasing on the eye though, for full efficiency they would need to track the sun across the sky on a revolving mount.
If I burned all my household rubbish instead of recycling it, that would be even better wouldn't it It'd save the faff of putting out the boxes every fortnight *and* heat my pool. Brilliant. Just need a tall chimney to get those smelly fumes away from my property.
Think it'll catch on?
Boz
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