Wireless Hot Water Temperature sensor

I wanted to add hot water temperature to my raspberry pi powered “Pimometer” but wirelessthings dont make a suitable XRF sensor.

I decided to buy a standard wirelessthings temperature sensor, unsoldered the thermistor and added a flying lead resoldering the thermistor to this, making sure to insulate the legs of the thermistor.

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Luckily (or not) our hot water cylinder has no insulation around the immersion heater at the top of the tank, using some thermal paste i attached it to the bare metal and taped it in place with some foil tape. I then added it to my pi and left it to get some readings.

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The final step was making sure the readings are relatively accurate, using a thermometer under the hot water i compared the real life temperature to the readings on the pi and to my suprise they are are only a couple of degrees out so definitely accurate enough for what I need.

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After seven days of data logging i lagged the hot water cylinder to see if there was any significant improvement in heat retention.

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NOTE: When first testing this setup I didn’t use thernal paste, the readings were around 30% out which was nowhere near accurate enough, by adding the thermal paste and angling the bead of the thermistor it has improved this considerably.

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