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boisdevie1

Another solar hot water question

As I understand it if you live somewhere where it freezes in winter they you need an indirect system. This means that you have anti freeze in the pipes and they form a coil in the water cylinder which heats the water in the cylinder.
Cheaper systems are direct meaning that water passes into the collector, is heated and goes straight into the water cylinder. But in winter you have to drain the system and use something else because if it freezes you'll break a pipe somewhere.
So far straightforward, but would it not be possible to have a direct system but instead of using copper piping you could use heavy duty hosepipe in the collector and then for the rest of the system use copper but well insulated. Then the hosepipe will be able to expand if it freezes. Does this sound OK or am I being daft?
judith

Other problems notwithstanding, I'd be worried about the hosepipe melting, not freezing.
RichardW

Daft sorry. Hose wont take the presure / heat. It will balloon up. Even the proper plastic type pipe work is only rated for 60 deg c in most cases.


Justme
dougal

You're missing a few points. So in one word 'daft' Very Happy

Its a bad idea to circulate fresh (new) water through the solar collector. You get more oxygen (so corrosion, biology, etc).
"Anti-freeze" also raises boiling point and increases the specific heat of the circulated water, increasing the amount of heat that can be carried away from the collector.
So "indirect" is very good.
A good collector is going to get *hot*. Not just too hot for hosepipe, but too hot for plastic central heating pipe.
And so a pressurised, pumped system is justified.
Navitron, for one will sell you proper evacuated tube collectors, dual coil tank, pump, controller, pressure reservoir, etc for less than 1000 all told.
If you really want to DIY as far as possible, with home-made (and rather less efficient collector) then you'll probably find a drain-back system simplest.
boisdevie1

Thanks for all the helpful advice. ONLY 1000 quid seems very steep to me given that I'm very tight. So I'd rather make my own system. After all, immersion tanks and copper pipe arent that expensive (certainly not 1000 big ones). I'm tempted along the lines of building a direct system for spring/summer/autumn use and then using the immersion coil in winter.
MarkS

might be cheaper to source the bits in France - although it will be a bit of a load on a bike!

Have you checked the prices of quality tanks with good insulation ? They are not cheap.
dougal

boisdevie1 wrote:
Thanks for all the helpful advice. ONLY 1000 quid seems very steep to me given that I'm very tight. So I'd rather make my own system. After all, immersion tanks and copper pipe arent that expensive (certainly not 1000 big ones). I'm tempted along the lines of building a direct system for spring/summer/autumn use and then using the immersion coil in winter.

1/ 1k *is* cheap for an evacuated tube system/tank/controller. For France or the UK.
If you are looking for significant solar contribution for 3 seasons, you need an evacuated tube system. And you'll probably not get any quotes for an installation under 3k.
And to reinforce Mark's point. You *need* a well-insulated tank.
2/ Pumping hot water from the tank through a home-made collector on the roof ("direct" system) will *cool* rather than heat the water for something like 300/365 days of the UK year. YMMV depending on location/microclimate/etc. Sorry but that is a bit daft.


If you have a hot tank in use with an immersion element, the cheapest way to incorporate any solar is to replace that element with a mini solar coil.
This shouldn't need any changes at all to the *existing* plumbing.
And you can hook whatever collector and controller you fashion onto that swap-in coil. It isn't the most effective but it *is* the simplest (and fairly cheap) way to start playing for real.
"Retro fit coil" 105 http://www.navitron.org.uk/pricelist.htm
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