Plumbed in

I finished the plumbing last weekend, the Solar water heater has been running for about a week now without any problems. We have had a mix of Sunny, cloudy, cold and rainy days so these variable conditions have enabled me to tweak the settings for the most efficient use.

I was initially concerned by the single inlet/outlet connection to the tank; the advantage of this setup is that you only need to run a single pipe up the roof to the tank, but I was worried that refilling would conflict with hot water use - say in the middle of a shower!  In reality however this rarely happens, as the system waits a min 30mins before trying to refill once the water level drops below 25%.

As first, I set the system up to maintain a tank level of 75%, this has the advantage of introducing less cold water for each refill, but I found on non-sunny days that the frequent refills still caused the electric heating element to come on more frequently as I also have the system maintain a temperate of 60c.

After a few tests, I found it was better to simply let the system empty down to 25%, this proved to maintain a much higher daily water temperature, especially on sunny days when it would heat up to 80c+ and the refill would not even dip it below 57c which is the trigger for the electric heater.

The 1.5kw heater seems to work very well, in no time the water is back up to 60c on cold days or a refill from the 25% level.

The only real negative point about the system for me is that the water pressure is a little low (I like to shower under a waterfall :-), but adequate ... so not a show stopper, I guess in fact it saves water which is a good thing.

Boiling Hot!

Here's a shot of the digital controller of my new Solar Water Heater. As you can see the water has almost reached boiling point after a couple of days in the sun. The tank is very well insulated and so looses very little heat during the night. Steam and boiling water is intermittently spouting out of the tank's vent hole like a mini geyser!

In normal daily use it should rarely reach these temperatures, as fresh cold water is added to replace hot water taken from the system. However, I'm happy to stress test the system like this to see what happens should we be away from the house for a while.

Ummm, I'm going to have to wait for a few cloudy days now to finish the plumbing .... it's far to hot to work on at the moment.

Solar Heater - Tube Installation

Installation of the 24 glass tubes was quite a challenge for several reasons. The pitch of our roof is very steep, so I had to fabricate a wooden support system to provide reasonable safe access to the heater frame. The manufacturer claims that the tubes can survive hail etc .... but these tubes are glass and would certainly break if I dropped one! 

Each vacuum tube slots into a hole in the tank with a tight fitting rubber seal. I used undiluted washing-up liquid as a lubricant, and carefully pushed each tube into place. The sealed, far end of the tube sits on a rubber seat in the frame. I can tell you that I was very relieved to get all 24 tubes safely in place.

Since I've not had time to complete the plumbing work, I temporarily sealed the input/output and filled the tank manually via the vent hole using the garden hose. I wanted to check for leaks and functionality before ripping out my gas water heater!

Once full, I noted the water temperature was 15c and the sun was setting. The next day was cold (5c) and very overcast ... surprisingly the tank temperature had dropped by only 1c overnight and was hovering at 14c. Later on in the morning, the cloud began to break and we had some sunny spells, within several hours the water temperature had reached 40c - very impressive.

Solar Water Heater

Ideally this should have been a summer project to take advantage of the hot temperatures .... anyway, I finally purchased the components on a recent trip to La Serena. The kit comprises of a ~300 litre tank, 24 vacuum tubes, support frame, backup 1.5kw electrical heating element and micro control unit.  It sells for approx. $600 USD. Our gas cost per month to just heat water is around  $40USD, so the system should pay for itself in less that 2 years.

I assembled the support frame on the ground and hoisted it up to the roof. Next came the tank, which when empty is not that heavy, but very bulky and difficult to handle . The project almost ended in disaster when the tank toppled off its support before I was able to secure it properly, but the hoist rope was still attached and I was able to grab it before it bounced off the roof! A few scratches, but fortunately no serious damage.

The next steps are to plumb in the tank, add the temp/water level sensor and electrical heating element. The glass vacuum tubes will be installed last to protect them from possible damage. Care will have to be taken for example to prevent thermal shock. The system operates at atmospheric pressure, thus the tank must be mounted as high as possible, else an additional pump is required to increase the water pressure, which I wanted to avoid so that hot water is available even during a power-outage which occurs quite frequently at this location.