Heating an outdoor pool

[Adrian]

deano ( [e-mail]) gurgled happily, sounding much like they were saying :

Wouldn't he (the missus/kids) like a nice hot shower at the poolside?

[deano]

I've read all your posts with great interest and I am considering the options.

My leaning is currently towards gas combi in the shed with solar top-up using a suitable pool cover.

I liked the idea of a zone off the main house CH but this means more disruption to the house, drawing from the house heating and possibly overloading the boiler. Plus I still have to get the new zone out into the garden and thru a heat exchanger with another circuit for the pool to linkup with the HE. This is as involved as piping the gas main from the meter [whichever side ;-)] to the shed. And would also provide for the gas fired patio heaters and barbeque he's considering.

The black hosing is also a beautifully simple idea but he just doesn't have the space.

Thermalac electric heater would be the simplest to install and if =A3500pa to run it is less than the cost of a gas boiler/solar cover combi and as instant then I'd certainly consider suggesting the use of one to him... any numbers (=A3's) on how the two systems compare?

On the route of gas fired boiler in the shed and thermal cover on the pool, my main questions would be... how redundant would the boiler become, once the pool was up to temp in the 'swimming season'? and could the thermal/solar cover then be relied upon to the keep the water at the desired temp? Do I have this right or will the gas fired heating always be in demand throughout the period? If the boiler is just to perform the role of starter motor, then it follows that the use of one may be uneconomical, however I do believe that my pal is looking for performance and results over economy and environmental factors... sorry, not my criteria but his.

Still in favour of the gas to shed, firing combi boiler, route is the desire for gas in the garden AND, in addition, using the HW side of the combi boiler to facilitate a shower by the pool makes me feel better that the combi is being fully utilised... and he gets another benefit, albeit at additional cost :)

If we're talking hundreds of pounds difference between the options then I need to make him aware, otherwise, he won't be that bothered and I'll be making my own job harder for little return. Another caveat is that a good friend of his already has a pool which he heats using a gas boiler and performance comparisons are always gonna be made between the two of them, before costs come into the equation. Plus his pool supplier suggested a gas combi and so has another friend of mine.

You can see where I'm going with this... I don't want to end up giving him a solution that meets my requirements and expectations but not his, and I don't want to give myself unnecessary or unappreciated work!

Thanks for sharing your knowledge(s)

deano.

[meow2222]

Whats round the pool? Has it been surfaced yet? If not, you can use the hard surfacing as a basic solar panel by putting pipes down before the coccrete / tarmac / etc. This method has been used to provide full heating before. Driveway, path etc can also be used if any is due to be surfaced.

a pool cover doesnt heat the water, it stops evaporation and provides a little insulation. The sunlight that goes in through a cover was going into the pool already.

If you want the water above average ambient temp, and theres no other heating, then naturally yes.

The difference is thousands, not hundreds. I get the feeling you've not done the figures.

why not do better and ask him what run cost he thinks would be reasonable, then say if you can design and implement something superefficient he gives you n% of what he saves over the next 3 years.

NT

[The Wanderer]

Thermalec recommend using a solar cover with their heater. As others have also said, the prime loss of heat occurs at the surface, the pool surface size - x ft x y ft is far more relevant than the nominal capacity of the pool. Ambient temperature and hours of sunlight will also have a bearing on comfort levels.

I was actually quite late in opening my pool this year. It wasn't until early June, coincidentally immediately after after I'd had my meter read. I had another reading mid September, and I closed the pool down just three of four days after that for winter.

I've used a little over 7,500 units on the E7 night rate between the June and September readings. E7 night rate varies according to supplier, but is somewhere between 3p and 4.5p per unit. In my case it worked out to something around £340 for three months, using an 18kw heater, surface size

14ft x 28ft.

That was strictly pool use only, heating and night time pumping. I have a three phase supply just for the garage and pool, so I can be qite certain about that. I also pump for three hours from midday when the sun is at it's strongest to get the benefit of solar gain from the bubble cover. Pool temperature averaged 90F+ for a capacity of about 9,500 gallons (about

42,000 litres) from June to Mid september when I closed down for winter.

Allowing that I was about 6 weeks late in opening the pool this year, my estimate of £500 for a full season ain't too far out. Bear in mind also that I run my pool quite warm. If your mate can settle at about 80F then his costs would be lower. He will, however, find that he'll have some difficulty getting anything like that temperature through winter without putting a lot more heat into the pool.

Oh, and those are actual, not hypothetical figures. :-)

There are a few websites out there that will have comparison info - google is your friend. Remember though that manufacturers have a vested interest in presenting any 'statistics' to their advantage.

[deano]

The whole garden is currently a building site... the plans are on paper and the pool area will be paved all around. So, by laying pipes underneath the slabs, would that make for an ideal secondary heating system? Anywhere I can look this up as to how to set up? Wouldn't a lot of heat be lost into the surrounding ground, rather than cycled back through the pool?

Ah! got that wrong then, I thought there was a cover that did both, using solar panels on the cover to heat the water via either an electric heater or cycled somehow through the cover using the pool's pump, as well as keeping heat in the pool.

Ok, so constant use of the boiler if no other system then.

You're right, I haven't. Anywhere I can study the formulas and equations used to do the sums and compare the results?

Not a bad idea, although my guess is that he has no idea whatsoever on the cost of running this, I'll give him a buzz to find out.

deano.

[Christian McArdle]

Insulate underneath to prevent this. It will only provide large amounts of usable heat in good weather, though. To get that all important April and October warmth, proper solar panels are a better bet. Still, if you're thinking of dino fuelled heating as your main source, it will signicantly reduce environmental impact as supplementary heat.

Certainly running the pump is a good idea around midday. This is because it circulates the warm water to the bottom and the cold to the top, getting more efficient heat transfer.

Christian.

[meow2222]

well, any place you've got hard surfacing you can run a pipe under. The more the better.

This type of collector is far from ideal from a thermal point of view, but solar is all about payback, which depends on install cost and return figures. Pipes under hard surfacing has the advantage that its very cheap to set up. All thats needed is some pipe, a low power pump and a thermostat. The nearer the top the pipes are, the more of the heat they'll harvest.

Look how hot tarmac gets in summer. It can melt. Despite its thermal inefficiencies as a solar collector, it does work. These type of collectors dont provide full heating unless you've got a largish area in use. However even a smallish area contributes and reduces both installed heating capacity requirement and run cost of gas or oil heating. What area of hard surface are you likely to have available?

Solar covers are basically long lived versions of bubblewrap. They let the sun straight in - there would be no advantage in capturing the radiant heat and pumping it in instead.

I suggested crossposting this thread to alt.solar.thermal.

I'd just say theres more than one option, and a superefficient system will cost a bit more either upfront or downline, but cost him less overall.

NT

[Peter Parry]

If its all dug up you might have a once only opportunity to install a ground source heat pump

use it to help heat the house in the winter as well as the pool in summer.

[meow2222]

[Peter Parry]

Possibly :-) Don't know a great deal about them but even an air one might be worth looking at.

[Andy Hall]

I've seen one used to heat a pool in Sweden. Pretty effective in fact.

[meow2222]

Theyre good where you cant get gas or oil to the pool heater. Use electrickery but at 300% efficient, loosely speaking. Install cost high though.

NT

[David Hansen]

On Mon, 16 Oct 2006 22:22:09 +0100 someone who may be Peter Parry wrote this:-

If they are run overnight on an Economy 7 tariff ground source heat pumps can work well and economically. A swimming pool, like underfloor heating, is ideally suited to one due to the low temperature output. Combined with a solar system to maintain temperature during the day it would be a good combination.

[deano]

Having mentioned the Thermalac system to my friend and the BPF of =A3500 per annum, it would now appear that this is the route he wants to go. His main concern is getting some heat into the pool pronto so that he can get the circulation going and avoid the water becoming stagnant, resulting in the need to get it shocked and back to ph... very expensive.

As previously mentioned, his pool is 20,000L it also has a jaccuzi built into it and he wants to use it all year round. The jacuzzi can be set up to get hotter than the pool and there are controls that allow the water from this to trickle over into the pool (providing some top up heat there).

So, I'm going to study the Thermalec site now and see what system requirements are needed.

cheers Dean.

[deano]

This is the actual pool he has had put in...

[The Wanderer]

Yeah, fine, just make sure he realises that his pool ain't the same as my pool, and my costs are for about 5 months use not 12 months use.

Having a pool *is* expensive, full stop.

Has the pool been plumbed up except for the heater? Looking at the website for the pool, it makes no mention of a filter or circulation pump included as part of the package. They're both essential for the pool. If they're not included, you can add, at a guess, another £500 - £600 for those before anything else! The inlets to the pump from the skimmers and drains should probably have ball valves or similar fitted, to assist when it comes to vacuuming.

It does, however, say a pool heater is included, also a solar cover, so I'm a bit puzzled now by your query about pool heating.

A Thermalec heater goes into the return pipe from the multiport valve on the filter to the pool. As long as there's space for that pipe to be cut and a Thermalec heater to be installed, there's no reason the pump and filter shouldn't be operated.

If the plumbing isn't complete, at least tell him to get some long-life algicide into the pool, it's available from any pool supplier. That'll help to keep algae under control, and at this time of year algae growth is quite slow anyway with relatively low ambient temperatures.

Err, this is getting more and more complicated. Dunno what sort of deal he's made with the suppliers, but in his shoes, I'd be pressing them for some more info. ISTM the pool suppliers have a lot to answer for.

As it happens I also have a separate hot tub, but that is much smaller, only about 800L. That uses a 3kw heater and runs at about 40C - anything less in mid winter will feel quite cool. It also has plenty of insulation within the body of the tub, and a very robust and well-insulated cover. I very much doubt he will get more than 2 or 3 degrees temprature difference between the pool and the jacuzzi.

I'm no expert on pools, but I've a horrible feeling you're getting out of your depth, and *you'll* finish up getting the blame if the pool doesn't live up to your mate's expectations.

[Peter Parry]

If he is going to use it all the year around he is not looking at GBP500 to heat it but more like GBP2,500 to GBP5,000 per annum, especially if his "Jacuzzi" is the open spa shown in the picture.

[deano]

Having spoken to Thermalec, specialist off ill at the moment, so info not from the company guru, it would appear that the size of the pool, combined wiith a built-in spa and my friend's desire to use the pool all year round, demands the employment of a 21kw unit, used on a 24hr basis, so no real advantage from using E7 power. A Thermalec heater of this rating, is =A31200 retail + carriage + VAT. On top of that, the cost of running the thing is going to be way more than =A3500pa. More like =A32000 (at least). Plus, I've just learned that the pool is actually 3,500L not 2,000L which changes things dramatically as you would expect.

AFAIK, the package he bought includes everything up to the Wall Plate (Heat Exchanger I presume) and only the heat source is required to get it all going.

He got a 'bubble wrap' cover and a winter cover in the deal, but I think the 'pool heater' must be a misprint, unless it means something completely different... will check that out with the supplier.

After speaking with Thermalec, I then called SwimTek (my pal's pool supplier) and had a good chat with the heating expert there. He was also on-site during delivery and installation, of the pool in question, and is therefore familiar with the site logistics and client's expectations. His opinion of the Thermalec heaters was that they represent the "Rolls-Royce" of electric heaters, a great product which delivers well on performance, reliability, low-maintenance and ease of installation, with a price tag to match, added to an already 'high cost', electric power source. With a 21kw heater, I'll be able to watch the meter spin, is what he said!

Therefore, I've decided to go back to my original route of using a gas boiler (either system or combi. Combi cheaper so far and with facility to heat pool-side shower, as suggested by Adrian). I can pick up a condensing combi with 80,000btu output for about =A3400, plus a pressure vessel system for about =A360. Groundworks to get the trenches dug for the mains water, gas and electric, from the far side of the house, to the shed is not an issue. He runs a demo company and has a JCB and groundworker on site, at his disposal, indefinitely. I have already asked that two trenches be dug for this span, to keep gas main separate from electrical cable. Also in the shed, a Consumer unit will be required, with fused way for boiler, say =A350.

A future project will require garden circuits to be hooked up to this with added ways to support, as yet, unkown loads; so I'll overspec the amroured cable going in the ground, from the meter to the shed... overspec cable is cheaper than digging up underspec cable.

To get mains water to the shed is a doddle and therefore negligible.

Other than that, to meet corgi regs, the shed will also probably need to be lined with a suitable fire-rated insulating material (need to get advice on this) as well as adequate airflow so the boiler can get fresh air and dispel exhaust fumes.

I also expect that there are rules governing the installation of both a gas boiler and a consumer unit, and their proximity to each other in a confined location, such as a garden shed. Will do some research on this.

Thanks, that might take the heat off somewhat (scuze the pun!)

Done that on his behalf and taking him out of the info loop has made things much clearer :)

Heating the spa separate from the pool is AIHBT controlled via the incorporated system, so that's an issue between him and SwimTek. They've installed everything up to the HE, leaving just the heat source to be installed! Even the electrical systems coming from the pool leave 3 cables that just need hooking up to a fused supply. When speaking to them today, no mention was made of a separate source for the spa, and I believe that would have been pointed out to me, but nothing's ever certain, so I'll raise this with them.

I appreciate your honesty and your concern. Yes, this is all new to me, however, there are two issues here: speccing a system and installing a system. I am up to the challenge of installing any of the suggested systems, but 'choosing' a system is where I had a weakness, which is why I began this thread. I hadn't even considered some of the alternatives that were suggested and having assessed each of them, even if to find them unsuitable, I have learned a great deal and am now much better positioned to advise my friend than I was to begin with. He knows I'm thorough, in whatever I do, and that's why he got me involved. I spoke to him today and, even though we've come full circle, he knows why.

I can also relax in the knowledge that my work will be inspected and approved by friends who are Corgi and IEE certified, before the system(s) are comissioned and connected to the supply(ies).

Thanks for your help.

d=2E

[deano]

Can anyone help me with the what regs apply to installing a gas boiler in the shed, as mentioned in my previous posts?

There are some requirements as to fireproofing and I need to establish whether this implies just the local of the boiler itself, i.e. behind and above the boiler, or if I need to line the whole shed with a suitable fireproof material, such as supalux or Gyproc Fire.

I have my own reservations about putting a boiler in a timber shed, but AFAICT it seems that this has been done many times before and I just want to ensure that by so doing, regs are not just met, rather, the installation surpases the minimum requirements for the locale. I'm even thinking of reccommending that my friend installs a fire/smoke detector with an alarm in the house to help protect the installation.

I've tried searching for info relavant to this but have so far not found anything specific.

Cheers, deano.

[Andrew Gabriel]

There are requirements for combustable sheds being a minimum distance from a house and from the property boundary. This is usually ignored, but if you're actually putting a boiler in it, then you should certainly bare this in mind.

Also, a wall mounted boiler will be far too heavy for the wall of your typical garden shed kit.

You can get boilers which are intended to be installed outdoors.