Make your dumb boiler smart DIY!

[Jovana (Jo)]

I have a 50-liter water boiler in my house. This one is very dumb because it has only 3 temperature settings and it is always on power. So when the power prices are high, this boiler will heat when needed.

https://www.ithodaalderop.nl/nl-NL/consument/product/07-04-18-045

For this project, I have used the Shelly Plus 1PM and a Shelly Add-on for a temperature sensor to convert this dumb boiler to a smart one.

and the optional temperature sensor (analog to digital)

(For The Netherlands I have purchased it from here: Shelly Plus Add-On | Home2Link) no-referral.

The setup
This is how I have done this (Please make sure you have switched off / remove the power).

1. Remove the cover from the bottom.
2. Now you can see it’s a very simple and basic (analog) device. In the center is a pipe where the temperature sensor is placed (it is an old fashion copper wire which leads to a power switch).

3. Be careful to slide in the temperature sensor (make sure you are not damaging the original one). Don’t push it too far, it’s not needed, it will take the temperature because this pipe is from copper and collides with the heat very well so the sensor is picking up very quickly.

4. Now bring the wire from the sensor to the back of the device, beside the power connector is space for the wire.

5. I have a small water and dust-proof box, where I placed the Shelly device inside. Cut the cable of the boiler and also work it inside the box where the Shelly has been placed. (Yes the terminal block for the groudn wire is not very nice.)
   

   

6. I have placed the box close to the boiler.
   

   

7. Connect the Shelly to the wifi network and add the device into HA. Now you can monitor power and temperature. Create automation to switch off when the price is too high. I have put the device in on max temperature so it will always start heating when HA switches on the power.
   

   

I will share later some statistics about before (always on) and after the automation has been enabled.

The promised update:
The first week I let the boiler go to have a good null measurement. It will heat the water to 65 degrees. It is using a little more than 15kWh a week.

After automation of the boiler and make sure it heats to a maximum of 50 degrees, and start heating again when it drops below 38 degrees. Now it is going to use almost 6 kWh a week.

I think this is a good investment! Also good to know, if the energy is real cheap or the price is below 0 it now can heat up to it maximum.

[oliwarner]

38-50°C is a really dangerous window for water storage as it’s well within the window to allow legionella bacteria to thrive. It breeds up to 45°C and survives up to 60°C. Your local building regulations might have advice on this (UK HSE recommends storing no lower than 60°C) but this isn’t geopolitical.

In domestic settings, storing in the 50s with a regular cycling up to 60°C might be acceptable.

[Jovana (Jo)]

Thanks for this good point! Yes, you have right about this. The danger of forming legionella is very low if the water is used regularly and not stored for a longer time. This temperature I have set for normal usage and higher energy prices. As I wrote if the price is cheap we store the energy in the form of hot water

[ddaniel (Daniel Dekovic)]

I have similar setup for a few years and had no problem at all. I don’t say that legionella isn’t a problem but…
If you ever bleed the radiator valve, and I do this regularly few times a year, than it’s much higher chance to get legionella from radiator water than from a boiler. I do this with out any mask or protection. In 14. years I’m doing this I never ever got legionella nor anyone in my house hold.