Archive for April, 2010

I’m in hot water

Wednesday, April 7th, 2010

I have a solar hot water system in my home; I think it works well but how do I know?  Well now I know.  I bought a simple data logger off of ebay and wrote  a perl script to load an rrd (round robin database) and presto:

What does it mean?  Red – is hot water output.  Blue is cold water in.  The Purple line is the bottom of the tank, when it is high all 160 gallons are warm.  The Green line is the water coming out of the collectors although during night it the water just sitting there.

In this chart which is about 24 hours you can see the water cooling off and then around 10 am the green line (the water coming from the solar collector) starts to heat up.  At first it raises the purple line (the coldest water in the bottom of the tank) and then it pushes up the red line (the hot water in the top).

Exciting, no?  I was impressed to get it working but the database part was way too hard for the casual user – I had trouble with it and I do this all the time.  I’m eager to find a practical solution for the casual user; as I investigate the options I’ll post them here.  Suggestions are welcome.