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Saw this simple setup on Marmaris main drag this morning.

I had one like that but with thermal tubes - bought from the other place- was very efficient - sadly got left behind when I drew a line under my first life I miss that thermal unit but definitely not the first wife

Moxi

Never seen that sort of thing in the UK. Very common around the med.

I guessed it was because even if the primary circuit was glycol, there was too much risk of the fresh water side freezing up and splitting in a deep freeze winter.
A

I had two in a row ( not wifes ) in my earlier life in Ireland . each 20 tubes and 180 l stainless steel tank with copper coil heatexchanger connected to mains water pressure and was very pleased with that decision

Ivan had one, with 47mm vacuum tubes, down in Hereford. He had no problem with the tubes freezing, even though full of water.

The insulated header tank would need to freeze solid, before the vacuum tubes would be at risk.

My main water pipe from a shallow well once did freeze in warm southwest Ireland , how would that happen with that thermal mass on-top of those panels ? But i might have opened a tap to allow a trickle flow

Oliver90owner wrote: ↑Fri May 06, 2022 9:06 pm Ivan had one, with 47mm vacuum tubes, down in Hereford. He had no problem with the tubes freezing, even though full of water.
The insulated header tank would need to freeze solid, before the vacuum tubes would be at risk.

Exactly. I didn't imagine the tubes freezing, but in mid-winter I could well understand the fresh water tank freezing up. One winter I commuted "over the hills" (while the roads were open either side of a deep snowfall and big freeze) and it was a great relief when the car air temp indicator came back up above minus 10! Minus a (single figure) was a landmark and surprisingly noticeable / significant! I would never have thought that the disappearance of a digit would be so noticeable.
A

AE-NMidlands wrote: ↑Fri May 06, 2022 10:02 pm

Oliver90owner wrote: ↑Fri May 06, 2022 9:06 pm Ivan had one, with 47mm vacuum tubes, down in Hereford. He had no problem with the tubes freezing, even though full of water.
The insulated header tank would need to freeze solid, before the vacuum tubes would be at risk.

Exactly. I didn't imagine the tubes freezing, but in mid-winter I could well understand the fresh water tank freezing up. One winter I commuted "over the hills" (while the roads were open either side of a deep snowfall and big freeze) and it was a great relief when the car air temp indicator came back up above minus 10! Minus a (single figure) was a landmark and surprisingly noticeable / significant! I would never have thought that the disappearance of a digit would be so noticeable.
A

well why would one use tubes filled with water , no go for me

billi wrote: ↑Fri May 06, 2022 10:29 pm

AE-NMidlands wrote: ↑Fri May 06, 2022 10:02 pm

Oliver90owner wrote: ↑Fri May 06, 2022 9:06 pm Ivan had one, with 47mm vacuum tubes, down in Hereford. He had no problem with the tubes freezing, even though full of water.
The insulated header tank would need to freeze solid, before the vacuum tubes would be at risk.

Exactly. I didn't imagine the tubes freezing, but in mid-winter I could well understand the fresh water tank freezing up. One winter I commuted "over the hills" (while the roads were open either side of a deep snowfall and big freeze) and it was a great relief when the car air temp indicator came back up above minus 10! Minus a (single figure) was a landmark and surprisingly noticeable / significant! I would never have thought that the disappearance of a digit would be so noticeable.
A

well why would one use tubes filled with water, no go for me

I was trying to say that the evacuated tube heat-pipe fluids contain something special that wouldn't ever freeze (but for some reason the old place said it wasn't acetone, I don't know why) but with no or little used waterflow and no sun in a long sub-zero spell it's obvious that the water in the useable water tank might freeze.
My solar thermal has something non-freezable in its heat-pipe tubes and 25% glycol in the primary circuit. Obviously the DHW cylinder is in the house - and of course the pump doesn't run when the collector is below zero. I have used the manual over-ride when it was below zero (just for fun) and the input to the tank coil gets bloody cold... A wet digit could have got stuck to it!
OTOH these gadgets look brilliant for where there isn't much risk of several days below zero with no sun. We have seen them all round the Med, and they wouldn't be so widespread if they didn't work...