Thermowell

Posts: 4

mcdonald_ajr, Mon May 18, 2015 5:42 pm

Thought you might be interested in my new Thermowell to measure temperature for my boiler. I was just dipping the sensor in the liquid, which works fine for the mash and the HLT, but even though these sensors are supposed to read over 100C and be waterproof, the PVC coating doesn't seem to like 100C for long periods, and becomes unreliable. So I spent many hours researching how to make a thermowell for the sensor and here's the result.

Sensors available via eBay (search for item number 400609703928 for the ones I bought). You'll need an Arduino plus some software to read them, which is another story. You could use any 1/4 inch (6mm) diameter sensor.
IMG_2489.jpg
Waterproof Digital Temperature Temp Sensor Probe DS18b20 - IMG_2489.jpg (22.31 KiB) Viewed 28583 times
Thermowell I got from RSonline (search for THERMOPOCKET R 1/2 100MM). Free delivery now which is great!
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Outside Boiler - IMG_2488.jpg (27.59 KiB) Viewed 28583 times
The cable gland I got from farrnell.co.uk (search for JACOB 50.007-F GLAND, BRASS, DOME TOP, PG7)

To fit this to the Thermopocket, you need a 1/2 inch to 1/4 inch reducing bush. bes.co.uk sell them.

And lastly, you need Angel Home brew's excellent system of stopping leaks, which they use on their taps, which is a 1/2 inch nut, two washers, silicone o ring and M27 washer.
IMG_2486.jpg
Inside Boiler - IMG_2486.jpg (25.26 KiB) Viewed 28583 times
I used a little thermal compound paste (Maplin sell it) on the end of the sensor to improve the thermal conductivity, and tested it out today by boiling some water in the boiler. Seems to work very well, with no leaks. I reckon it reads maybe 1 degree C lower than the actual liquid temperature, but I can compensate for that in my software. It does take a little longer to react to temperature changes due to the larger thermal mass, but that's not really an issue.

If you are wondering why I need to read the temperature in the boiler, I run two kettle elements, and once the water is boiling, the software throttles them back to an adjustable rolling boil. Usually 50% power to each is sufficient.

Hope this is useful, happy brewing, Anthony

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Posts: 78

angelhomebrew, Wed Jun 10, 2015 7:51 am

Thanks for post Anthony. Very informative

Note we have the PT100 probes now and looking into thermowells too.... Not literally ... You know what I mean :)


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