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Electric water heater starting cold, charted (Read 2243 times)
electron
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Electric water heater starting cold, charted
Feb 14th, 2011 at 3:01pm
 
This is what an electric water heater does when it starts cold. (see chart below)

Sensors are on one of the two wires going to each heating element. Remember you are not seeing water temp, it's wire temp, the tank ended at about 125F when it was done.

You can see where the top element turns off and the bottom one turns on, the bottom one is set lower than the top one, but yet it ran longer, not sure why.

You are seeing a little bit of the tank temperature because the sensors are under insulation and near the tank where the wire is and also under the electrical cover.

Just before 3PM I ran some hot water to test the temperature, you can see the lower part reacting to that, then the lower element comes on a little later. Now you can see what it costs to wash your hands in warm water!

Then you can see the upper part getting the heat from the lower part. Interesting, it looks like about 1 minute maybe.

If I ever put in one of those outdoor solar collectors on my tank somehow this should pick up that temperature change nicely, so I can monitor that too.

That was about a 4.5 KWH total run. This is a 40 gal tank with 2 4500W elements running on 240V AC.

You can start to get an idea of what it would take to run your water heater from a set of electric solar panels, or a wind turbine / generator.

Every day I log about 1 KWH with the water heater just sitting there, not using it at all! If I wash my hands like normal in warm water a couple times a day, it goes up to around 1.5 KWH a day!

For logging I'm using the DS18B20 "One Wire" Temperature Sensors.

#0 : Top heater element
#1 : Room Temp
#2 : Fan outlet, back of computer, just for fun
#3 : Lower heater element
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