2011: the year we made contact

Indeed it was a good year! we made contact! with the boiler, via OpenTherm! it has been running for over a month, with little to no hiccups. There are still some bugs to be ironed out in the daemon listening to the whole thing, but that will happen soon!

This weekend I hope to finish the whole project in terms of hardware, the boards have come back from fabrication, and I will assemble it this weekend and get it in the box!! hurray!! So stay tunned for a new post soon!
Meanwhile, here is a snapshot of the boiler data:

boiler data of the last 8 hours: black-setpoint; gray-water leaving the boiler; blue-water returning; yellow-pump running; dark blue-domestic hot water demand; red-flame active

Also in 2011 the garden door got automated, with an RFID reader connected to a JeeNode. Also that has been running fairly reliably. I had some issues with power, as the whole thing, even with some basic power saving was draining the batteries very quickly, so I added a small 6V solar panel, which has so far been capable of loading the batteries during the day, even in the shortest days, with a covered sky. I must say, it is very convenient to be able to just show a card to a door in order for it to open, instead of having to search for the keys in your pocket, and find the keyhole, in the dark and under the rain!

On the software front, I made significant progress on the dashboard, and that will be the next major project to tackle, and I built a little movie center - a small computer based on a mini-itx board, with a big disk, where all (or almost all) my DVDs are saved. Any movie (that I have) is now at the distance of a menu and a click, instantaneous and easy to browse! it uses XBMC! Great package!!

For this year, like mentioned above, I plan to finish the OpenTherm project, and maybe even improve it by making a self powered version (JCS from the bits and bytes is working on it...I don't really understand how it works), finish a version of the dashboard which will be installed in a tablet a friend is getting me, and then develop water sensors to put in the crawling space under my house, as I get water there sometimes, and I want to be warned about it! Also on the water front, I want to make a sensor to detect a clogged main sewer pipe (It happened a few times and it is annoying), and of course, automate the water readings, the only one not yet automated!

I realised yesterday, that I have been collecting data automatically since 2008, so 4 years worth of data! I would also like to do some statistical analysis of that!

Lots of plans!

Now I'm in the mood

For doing calculations, as I have to ascertain whether all the effort was worth it or not.
So, I have this curve fitting against which I can compare my gas consumption based on the average outside temperature for the month. But his is done for a month, and I wanted to see if I could go to a lower level, so I found in the KNMI website a service from which you can download all kinds of meteo data for a time period.
I downloaded the average month temperatures for "De Bilt" as that is where I have been basing my calculations all these years, although not the closest station, and plotted it against the daily gas consumption. I couldn't go away without putting it here, so here goes, for the month of November:

Considerations on the boiler system

The behaviour I mentioned at the end of the last post, does make sense.
That is, for the boiler to overshoot by a few degrees, once it has reached the set temperature, and by those means bringing the return temperature to the set point is the only way of avoiding it to cycle more.
Once the boiler stops burning, the temperature of the outgoing water drops almost immediately to the return temperature, so to avoid it turning on again, the return should be close to the set temperature, and that is what the boiler is doing, thereby keeping the water in the whole system at the set temperature, and not at the return temperature that happen to be there when the set temperature was first reached... (I hope someone can make sense of all this rambling...)

The system , with the DIY OpenTherm master, has now been running for a few days, with no problems, and quite an accurate temperature in the rooms. The PID controller just needs some small adjustments in order to converge a bit quicker, and converge always (I sometimes have 0.2 degrees below the set point, which is no big deal anyway...)

I found a few graphics depicting the boiler efficiency as a function of the return temperature. Here are a few, all in Fahrenheit (didn't find any in C):

http://www.mnshi.umn.edu/kb/scale/boilers.html

http://blog.triangletube.com/blog/hydronic-heating-solutions/outdoor-reset-maximizes-spring-energy-savings

http://www.navitron.org.uk/forum/index.php?topic=9066.0

The last is not the efficiency, but the relation of water temperature to outside temperature that I am using. I use a curve near the "1" curve.