Average performance- Navitron 20 tube?

[Poolguy]

If I was Spec'ing that system in France then 250lt would be paired with 25 x 47 in the South with radiation up at 4.5-5kw/m2. It would produce the temps most all of the time to combat leigonella. Further North (3.2kw/m2)I would say 20 x 58. If your going into the UK you have to realise the extent to which the radiation is more feeble, the number of cloudless days are fewer and the greater HW demand.  So I'd be thinking hard about 30 x 58mm on the basis that its easier to dispose of excess heat than it is to find heat when its scarce. After all the system operates virtually free of cost and its there for life. So the Difference in investment is better value for money all those thing considered, than many other purchases around these days.

I just don't get the tendancy to skimp on system design - it doesn't make sence to me. Why would anyone start to build something which is so underpowered that its struggles with its task most of the time. What is wrong with 'ample'.

Its a struggle of logic I face nearly every day with customers who cannot comprehend the basic idea that this system only 'collects' heat that's lying around, it doesn't create anything. I alway say that 'the more you can collect, they more your can store for when you want it.' Make hay (heat) while the sun shines. n'est pas

Andrew

[billt]

As the solar irradiance at the top of the atmosphere is only about 1300W/m2 your 3.2-5kW/m2 look rather optimistic!

I can understand the tendency to skimp perfectly. A professionally installed solar system is expensive, adding more tubes makes it still more expensive. As solar heating can't be reduced to simple numbers it's difficult for the non-technical to make an informed decision. Paying some multiple of a hundred pounds extra is likely to stop most people installing a system at all. Especially as such a system for DHW only makes no economic sense.