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| WHO USED ALL THE HOT WATER!!! Need a simple temperature data logger ** UPDATE ** |
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| Brumby:
This data is from the simplest, quickest and easiest install possible. You have to start somewhere. There's no point building a Cray to see how well your binary adder works. Refinement will follow - if it is required. Even so, this unsophisticated setup has delivered some interesting data. From what I can estimate, thermal inertia is about 30 seconds for the current setup. Differentiating hot water events a minute apart has not been difficult with the data collected so far. Even then, if there are a number of short events close together, then the amount of hot water involved is not significant, so distinguishing each of them is unnecessary. If there is a need to get so particular, then the security footage is timestamped as well and it would be trivial to match traffic and temperature ... albeit a bit time consuming. 7 minutes is way, way outside any time constant resolution required. The first 30 seconds after water has stopped flowing is clearly visible and unambiguous. If water starts flowing again within that 30 seconds, then the inertia will still result in a small, but visible dip unless it was only off for a few of seconds. In that case, it is highly likely it is the same person ... and in the case of the (rather unlikely) need for full clarification in such a situation, security camera footage is available. It would be good to get the water flow rate, but it's not clear whether such information is necessary to achieve the desired goal. That goal, by the way, is not to convict, but to initiate a conversation. Please keep in mind the purpose of this exercise is not to track every millilitre of water and every millijoule of energy so you can bill each person for the cost. |
| Dundarave:
Have you considered simulating actual showers of different lengths in order to determine typical usage “signatures”? Once you have several known patterns of actual usage, you ought to be well equipped to interpret accurately (i.e. accurately enough for your purposes) the real-life usage patterns that get recorded. |
| Brumby:
Tank heating is done on an off-peak tariff, so the element is switched on at given times, depending on thermostat. One further bit of data from overnight... tank heating. Because the sensor is on the outlet pipe, heat conduction from the tank does affect the temperature it reads. During tank heating, the temperature profile was quite distinctive. The sensor temperature did rise, but much more slowly than when hot water flows and it levelled off at a lower temperature. At the end, the temperature drop was again quite different to flow cessation. The fact of the time of day and the 3 hour duration distinguished this event from any other. |
| Brumby:
--- Quote from: Dundarave on August 24, 2023, 05:05:58 am ---Have you considered simulating actual showers of different lengths in order to determine typical usage “signatures”? Once you have several known patterns of actual usage, you ought to be well equipped to interpret accurately (i.e. accurately enough for your purposes) the real-life usage patterns that get recorded. --- End quote --- Absolutely! The first step is to see if we can get some data which has sufficient distinguishing features to allow such profiling - which we seem to have. I have already done several "hand washing" exercises to see how they show up. I have also been making notes of when others have done things of note (See the chart above). Today I have noted an honest-to-goodness shower event! Special exercises may come further down the track if there is need for clarification. |
| floobydust:
What are the chances the tank is undersized for the number of people taking showers? How big is it. Looking at US hot water tank manufacturers, their recommendations seem a bit nutbar: For 1 to 2 people: 30-40 gallons For 2 to 3 people: 40-50 gallons For 3 to 4 people: 50-60 gallons For 5+ people: 60-80 gallons I calc 20 US gal (76L) is 8 minutes with a low flow 2.5gpm shower head. |
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