Context

Grohe Blue Home is a box that you place under your kitchen counter. It is connected to the mains water line and it provides cold and fizzy water.

This box is basically at fridge + carbonator. The fridge cools the water while the carbonator adds CO₂ to the chilly water in order to carbonate it.

Like all fridges, the heat must be dissipated in order to cool the water. Grohe uses a fan to force cool the heat exchanger.

However, this fan is of really poor quality. It’s powered by the mains voltage (230V) and makes soo much noise that the appliance becomes a burden to have.

The goal of this weekend project was to change the fan in order to lower the noise made by the carbonator.

Fan search

The fan included in the carbonator is a SUNON DP203A. 122m³/hour and 120mm×120mm. The datasheet indicates that the noise is 32 dB, but I measured 47dB(A):

I decided to buy a Noctua NF-P12 redux-1700 PWM. The PWM capability is somehow useless, because the carbonator only toggles the fan when the compressor is running. I guess I could’ve modulated the speed given the temperature of the condensor coil, but I wasn’t that motivated.

Both fans have basically the same airflow, so the COP of the heat pump won’t be degraded.

Good news, the noctua is twice as quiet, at 38 dB(A):

Next step was to design a small spacer in freecad, and then 3d print it, because the noctua was slimmer than the original fan:

And it was just a matter of inserting the new fan. As you may notice in the following picture, the Noctua is powered with 12V.

Sadly, the grohe doesn’t have a 12V power source. There is a 24V transformer that is used to power the carbonator pump, and a small 7805 that powers the logic board. I couldn’t find a 12V source so I hacked together a small 12V power brick.

It’s totally overkill (the power brick can deliver 1A), but I thought that as it’s only powered on some hours/day, it shouldn’t impact the energy consumption that much.

And now, it works and it’s much quieter during the night. Cheers!