This project is an Arduino based timer to control an office hot water system over weekends and holidays to save the business just that little bit more energy. These project files are the casing for the device, the Arduino program, the user documents, and spreadsheet to set up the holiday periods.I worked for EECA (http://www.eeca.govt.nz) the Energy efficiency and Conservation Authority for a number of years during which time the NABERSNZ energy efficiency rating scheme for commercial buildings was introduced. EECA got its tenancy assessed and gained a 4½ Star Rating which is reasonable but meant that there was still room for improvement. The office's Energy Champion was keen to see the office reach the five star rating. In his monitoring of the office's energy use he found that the hot water cylinder servicing the Men's and Women's showers and bathrooms were still active during weekends and holiday periods. To fix this he introduced a timeclock to the system to disable the hot water cylinder elements during these periods when nobody would be using these facilities. Once the timeclocks had been installed the energy use records showed up a strange quirk of the timeclocks – at the stroke on midnight during the weekend, the time clocks would enable the hot water cylinder elements for one minute before disabling them again. This resulted in a 30kW spike in demand every midnight over the weekend as the elements all turned on to make up any lost heat. Although one minute at 30kW was not a huge amount of energy it potentially influenced the electricity charge for the period because it set a high maximum rate of consumption. The problem was found to be that the timeclock could not handle programs that spanned between days. The challenge was to come up with a system that could handle weekends and holiday periods. These project files are the casing for the device, the Arduino program, the user documents, and spreadsheet to set up the holiday periods. All information on using the system is in the document files. As for the 3D printed bit, Blender files and STLs are provided for the box. Originally I was just going to download an Arduino box off Thingiverse seeing as there were so many of them, but I found that nothing was quite what I was after and so I designed yet another one. There is a small opening on the front into which a bit of clear waste plastic can be glued. This is so that the indicator LEDs can be seen when the device is installed. The two halves clamp together with some threaded rod and nuts. Only one half of the casing is shown in the photo. There are two sets of Arduino Code provided. One is to drive a NORMALLY OPEN relay, while the other is for a NORMALLY CLOSED relay. For more information on this project go to http://www.techmonkeybusiness.com