DIY solar water heating project - any comments?

I want to install solar panels to contribute to water heating. This is a 4 bed house with currently only 3 occupants but capacity needs to be adequate for 4 - 6 people I guess.

Current system is entirely conventional gravity fed and open with gas boiler.

Boiler is over 15 yrs old and is weeping along some joints so due for replacement this summer. At the same time we want to fit a bigger cylinder with 2 coils as the current cyl is only just adequate for 3 people.

When funds allow I will then either buy or construct a collector. I have started looking at vacuum tube collectors but am beginning to think these will be too expensive for my project (I want to do it as cheaply as possible) and I'm worried about the fragility - the roof faces south west and is exposed to westerly gales coming from the Irish Sea about 15 miles away.

So my present thinking is a conventional collector with a solar powered self-regulating circulation pump feeding the second coil in the new bigger tank.

How do you prevent the water from boiling in the collector in summer? By early afternon the sun is beating down on our roof and the attic gets flippin' hot so I reckon boiling is a possibility. Would the circuit need to be closed or open with a header tank and expansion pipe?

My neighbour is a retired plumber who installed his own panels 20 years ago and is keen to help me with this as the poor bloke is bored.

Full sun with no water demand is a problem - real world tests are the only way to be sure that the panel can survive I'm afraid. A good panel will get to well over 100 degrees C - so you're wanting a pressurised system, expansion tank, safety vents and the likes - and high temperature solder...

Fragility an issue with many commercial systems as well as DIY ones. The *only* solar water heating systems to have been properly tested are made by Viridian. (disclaimer - I've met Stuart and chatted about his firm/products, and tend to agree with the bloke)

http://www.viridiansolar.co.uk/home.htm

They're also designed to be stupidly easy to fit (just like a large roof tile):

http://www.viridiansolar.co.uk/Products Install.htm

They (unlike the monstrously expensive vacuum tube affairs) are sized/specified so as to make genuine economic sense, and Stuart (unlike other firms) does not present dubious numerical information...

http://www.viridiansolar.co.uk/Products Performance.htm

Funnily enough, as a result they're the only firm I'm aware of that are trusted by and working with penny-pinching housing associations and commercial builders...


If it were me, I'd be seeing if they're not interested in a DIY install.

Install a system boiler and pressurised hot water tank/system in the attic and get that all working. Later you can remove a chunk of rooftiles and fit the solar panel. Roofing is a piece of cake - nothing that joe bloggs roofer wouldn't have seen before with skylights. Later the plumbing - again nothing that joe bloggs plumber wouldn't have seen before - but make sure they're suitably clued up to work on pressurised hot water systems. Wiring - plug and play...


I'd be very surprised if you can put anything like a properly engineered system together for the price of the Viridian systems, but appreciate that they're maybe a bit early stage at the moment.

Thanks. Very helpful. This looks an excellent system, I especially like the way the panels are integrated with the roof. They have quoted me £1360 + VAT + delivery for 4 M2, which is pretty good.

it might be worth looking into ground source heat pumps if you have the garden room to spare ( ie under a lawn, not landscaped.. it involves digging a large pit.. )


from what I've read, they work like an air conditioning system but the condensing coil is burried ..

Ah yes, our neighbour is doing this - he's got an acre of paddock.

We've probably got 100 acres out the back but it belongs to the farmer so that's a no-no!

I have pondered on this as we have ample space for the heating coils. The drawbacks are mainly two: the heat obtained is low grade so it's more suitable for underfloor hating, and thus unsuitable for retro-fits, and the high cost of the boiler (£7.7k?) and install (£?k) makes payback a long long time.

£10k+ in an investment bond gives £500 pa tax free for 20 years, with a chance of a decent return at the end. That'll go a long way towards subsidising the cost of one's more responsive existing system.

you can get grants for these things.. it's nowhere near the full price but it goes some way to paying for it..