I used two digital thermometers to measure the in and out temperatures of the heat exchanger under the shower cabinet. Each thermometer was strapped with a rubber band to where the pressurized water is connected to the Miljødusj, one on connection 1 which is incoming cold water, and the other on connection 2 which is the preheated water going to the shower.
My initial test setup was performed by cooling it all down first. I let the cold water flow in the shower for 5 minutes, then I took a quick shower. The plot clearly shows how the temperature of the out pipe to the shower increases from 15 to 26 °C (59-80°F) . The lowest graph shows the temperature increase which is about 11 °C . (The increase after the 6 minute mark is after I stopped showering).
The day after I measured my own shower which is usually fast, followed by our oldest son, Simen, who takes longer showers. ( Yes, teenager..) Looking at the graph you can see that the temperature in the room, and then also of the initial water in the heat exchanger, is 22 °C. When I start to shower the red curve shows the temperature of the preheated cold water pipe going to the shower. It is increasing all the way along as we shower. The blue curve shows the temperature of the incoming cold water pipe. Looking at the second shower you can see that it bottoms out at 14 °C . After a shower it heats up due to the last drain water passing through the Miljødusj and also later from the room temperature. The lower curve is just the difference between the two upper ones, showing the temperature increase, which is really what we are looking for. The difference show 11 °C . But is this the real temperature increase of the water? No, it is the temperature increase measured on the outside of the connecting pipes. If you recall the pictures of the inside of the Miljødusj, the out pipe goes from the back of the box and above the drain water back to the pipe connection to the shower. I assume the pipe temperature here is close to the water temperature inside the pipe. Around 25 °C . The incoming cold water is out of the picture I managed to take, but it is most likely very close to all the parallel pipes and in contact with the drain water. To check for this I just measured the cold water coming out of the tap. It showed 11°C . So when I measure 14 °C outside the pipe, the inside water is really just 11 °C. I am confident that the real cold water temperature increase in our shower is close to 14 °C (57 °F) from 11 °C to 25 °C.
Continue reading here: 6.Can the washer machine benefit from the Miljødusj?