Monday, January 7, 2013

A hot water storage tank and central heating temperature monitoring system

This is a short description of the central heating temperature monitoring system that I have installed in my house. It's an ongoing project which only seems to grow as time goes. :-)

The system keeps track of indoor/outdoor temperature, radiator inlet/outlet temperature, wood furnace heat transfiguring and effect and the hot water storage tank temperature. The hot water tank is actually measured at 7 positions evenly distributed along the tank from inlet pipe to outlet pipe. By doing this I can actually see the level of hot water in the tank and predict when the tank will be empty.

The measuring is done via a 1-wire network with 14 connected DS18S20 temperature sensors. The network is then connected to an Arduino based display unit. The display unit gives current status and is able to log and display up to 4 of the sensors with 128 samples each. This is because of the limited RAM in the ATmega328p.

The expansion plan now is to create a logger on the 1-wire network which logs all the data on the display with some interval. The logger will have wifi connection and an SD card so that I will be able to check up on the current status from my iPhone and even from the Internet when I am not at home. The logger will also be Arduino based. I guess that maybe I should have gone with a Raspberry Pi instead but I had already gotten some parts for the project when the Pi was available. And also it will be more of a challenge to fit everything into the ATmega328 :-)


  1. Bravo, Jonas. I live in Kansas City USA and am attempting to start a similar project to yours but which would also control a pump to circulate the hot water through a radiant floor loop system. Please continue to update your advances as I am very new to Arduino. Thanks! KC MEI.

  2. Hej Jonas!

    Very interesing job, regulating use of a wood furnace is an uncommon problem to solve. One thing is unclear to me though, and that has to do with the sensor placement. As far as I can tell DS18S20 is a "dry" sensor, how are these attached to the tank and what are they in fact measuring?

    I can see that you have analog sensors on the tank and probably on the furnace aswell, do you utilise them?

    Vh Oskar