using a shower unit to heat a swimming pool

[Smithwood456789]

as a conventional above ground swimming pool 15 ft dia heater (electro) is just a heating chamber, cold water in one side passing over internal heating element and warm water out coupled into the filter system with a temperature control and safety cut out is there any reason why a shower unit could be used instead. They have the same features and reqirements and the filter pump delivers the necessary flow rate. They come in 3kw, 4.5kw for this size pool. Coupling the shower unit to the filter pump water circulation is not a problem nor is the electrical supply in this instance. The only difference that I can see is the price (£300+ for the pool heater as opposed to anything from £50 to £100 for a shower unit that meets the flow rate and KW requirements) Is this possible do you think or an impending DIY disaster! I would be most gratefull for any guidance offered before I take the plunge, so to speak. My plumbing and wiring skills are now more than sufficient to tackle this so that is not a problem.

Josephine Smith

[Wanderer]

Several things come immediately to mind. What size is the existing filter pump pipe-work? Is the shower unit pipe-work of similar size or smaller? Will connecting the shower unit reduce the flow-rate appreciably? Will the shower unit withstand the chlorine levels withing the pool? If you use slow release tablets in the skimmer, the chlorine levels will be appreciably higher than the body of the pool water. Also the shower unit *must* be wired so that it can only come on when the pump is running. It is also prudent to operate the pump for at least 30 mins before and after the heater unit, to minise the risk of scale build up.

I am assuming that you have all supplies to the pool electrics fed by a

30mA RCD device.

[Wanderer]

Hmm, pool heaters are essentially un-vented flow boilers (albeit with an excess pressure safety valve). It's the passage of water through the boiler that keeps it operating safely. They *must* be wired so that they only work when the filter pump is on. I think you'd need to get some sort of cylinder that was little bigger than the bore of the (usual) inch and half diameter pipework.

[Bob Mannix]

How about a combination:

PUMP ____ =========/ \================================== >>>>

=========\____/= ==================== ========= || >< || ||________|| >< | _________| || ___||___ || | | || | | || | | || | | || | | || | ~~~~| ||______| | | _______________|

~~~~ Immersion heater with thermostat in vented tank

The thermostat would prevent boiling in the normal way if the pump failed.

The first flow restrictor could be set so the pressure in the tank during pump operation was not sufficient to blow water out the vent.

The whole heater section is an "add-on" that can be isolated for repair.

[BigWallop]

But I really think this is the type of thing you should be looking to fit if you're thinking of using your pool over winter.

[Martin Angove]

Reminds me of the tricks people used to get up to in order to warm the water in our church baptistry. My earliest memory is of a device about

4ft tall (the electrical connection box was just out of the water) which stood on the baptistry floor like a tubular metal foot. The church we borrowed it from had 15A round pin plugs, and we had to put a 13A square pin on for it to work - the plug used to get very hot but the fuse never blew.

Then someone had a bright idea. They bought two galvanised metal buckets and fitted a standard immersion heater in each - the idea being to float the buckets on the water. Even at 12 I could see that that was a bit dodgy.

When I was baptised the water was more-or-less cold straight from the tap (via a hose) though we did fill it up the previous day and leave the feeble church heating on. When my sister was baptised, all three of the aforementioned heating devices were used and it was like a sauna.

Several times I, personally, spent hours in the church boiling and re-boiling the tea urn and kettles to try to take the edge off the cold.

Nowadays, of course, it's been plumbed up with a cold tap and hot water through the hall's combi boiler. It doesn't exactly fill quickly (I'd say it is about 8ft by 5ft by 4ft deep, ignoring steps) but now that it's been GRP lined it fills slightly more quickly than it used to. Just before the decision was made to line it, it would lose 6" in about an hour.

Hwyl!

M.

[Christian McArdle]

Whilst I realise that a commercial heater is likely to be unvented, I think a DIY solution would be much safer with a conventional vent. Then you don't have to worry about explosions so much. As long as the vent is higher than the head produced by the pump plus a bit to spare, it shouldn't pump over. Relying on the pump to keep working or a flow switch to work doesn't seem as safe as a 2 metre length of pipe, which has fewer failure modes. Obviously, the heater would be interlocked with the pump supply anyway, so there are at least 2 safety devices.

Christian.

[Wanderer]

How do you come to that conclusion? Do you have any figures to substantiate your claim?

I use an 18kw flow boiler with my pool, (10,000 gallons) and that brings it to a temperature of about 27 or 28C without any problem, at an annual cost of about £300. With solar gain through the buble cover, the pool has been at about 32 or 33C for the last five or six weeks.

That presupposes you have room for the panels. In my case I don't.

[Owain]

"Martin Angove" wrote | Reminds me of the tricks people used to get up to in order to warm the | water in our church baptistry. | Then someone had a bright idea. They bought two galvanised metal buckets | and fitted a standard immersion heater in each - the idea being to | float the buckets on the water. Even at 12 I could see that that was a | bit dodgy.

You don't need an RCD if you put your trust in Jesus!

Owain

[NickW]

Off peak electricity 3.25 p per kWh Oil is about 1.4 p per kWh

Oil boilers are less efficient than heating by electricity but even so you can already appreciate the difference.

I have an oil boiler too, I just prefer to use 'green' energy where practical - and save some cash to boot.

Failing that, oil is best in terms of both cost and probably green-ness too because of the efficiency loss associated with burning coal in a power station, making electricity, transporting it through substations etc. and converting it to heat at the other end.

Nick

[N. Thornton]

It is in fact possible to heat solar without panels. Nearly vertical reflective sheets can be used to direct sun straight into the pool. Its cheap and simple, and when you use the pool you can draw the reflective curtains back so you dont get over-sunned.

There is usually room for these, tho certainly not always.

Regards, NT

[NickW]

Then there is Nick Pine's slightly eccentric black foamboard raft idea... see alt.solar.thermal