A couple questions. If you were to do it again would you still use the evacuated tube system or go with flat plate ? Why ? How long have you had the system and where are you located ? Do you know if either the wet tube or heat tube can be used as an open drain back system ? I use very little domestic hot water and plan to heat a large water bank for supplemental heating. With your experience with the evacuated tube do you have any suggestions or ideas for my plan ? If you don't mind (or maybe in an email) who is the manufacturer of your evacuted tubes ? Thank you Ross, Dave B.
Would I do it again? In a heartbeat.
Would I use evac tube or flat plate? Well, evac tubes are a little more expensive but they produce far "better" hot water I think. They are capable of producing VERY hot water.
The day I put mine together, I was still playing with it and perhaps not affording it the respect due. I carefully primed it before the sun came up (so I didn't get cold water against hot glass), and thought little more of it. Well, I went to have a look at it a couple of hours later and it was like a huge coffee percolator. Shooting a column of boiling water and steam about 10 feet in the air via the overflow vent I had (fortunately) put in "just in case".
After that, I did some considerable rethinking of how to tame it, and have a sensor at the "hot" end of the manifold, which directly controls a circulating pump. By adjusting the temperature the pump starts at means I can control the temperature the water comes out at. I currently have it set at 65 deg C (about 150F), and the pump just cycles as required. Over winter I had a lower setpoint because I was using the heat for hydronics as well as domestic hot water and the lower temperature suited my needs at the time.
I only got around to installing it in April this year (end of our summer - I'm 36 degrees south). I live underground, so the array sits "on the ground" which is really about 5 metres above the house "floor level".
Here's the thing during assembly. Sorry, nothing really as a size guide - but the stand is just over 6' high
Both systems can be used as drainback, although wet tubes obviously hold a lot more water so your drainback system will need a decent capacity. Also, the construction of most wet tubes don't really lend themselves well to drainback because only one end of the tube is open - and in order to prevent air pockets, that end is higher so they tend not to drain out well. (Only really a concern if you get freezing weather and don't want to pump warm water into the tubes to prevent damage).
I have two quite large hot water tanks - around 2,000 litres each (about 500 gallons each). Rough Plumbing diagram follows: