Unintended excitement.

[SpeedEvil]

What fun have people had with renewable systems?

The highlight so far for me was finding out I wasn't getting proper flow through my cobbled-together solar-thermal system from ebay by hearing an odd noise from the attic.

I got up the ladder, to find the unsettling phenomena of a repeated banging noise.
After turning on the lights, I found that the 'header tank' I had, which was made from a 3l juice concentrate bottle with a hosepipe leading into the rest of the system, was jumping, and a bubble of live steam was popping into the bottom, flash condensing, and then sucking the water down the pipe, to repeat a moment later.

I managed to remove the airlock eventually, by shutting off/on the pump repeatedly - which made the nastiest noises while pushing water through the manifold.

Needless to say, the system got a little more preparation for 'oopses' after that.
Still working fine.
Well - not this month mostly.

[guydewdney]

seriously? you are using a hose pipe and a juice bottle for containing boiling water? At what point will they soften and dump their contents through the ceiling? If its just a temp testing thing, thats one thing, but if you are more permenant than this, then may I suggest a metal pipe and a metal header tank (old copper tank? watering can?). The header tank needs to be sized so that there can be considerable expansion.

[SpeedEvil]

It was temporary.
In this case, I 'knew' that no way could any significant heat propagate to the bottle, as it was on the end of a 2m vertical pipe, and the thermal expansion of water would be a few tens of ml, not even coming all the way up the pipe.

the 'header tank' was more for convenience of system filling.
I'd intended to fix it the next day.

[Baz]

Thermal expansion of water is 4% over the temps solar sytems work - suprisingly large.