Hovenga Nano Brewers fridge build

Here’s our newly fridge hack with the new BrewPi spark.
The biggest problem in this build was actually the cabling runs. Everything was foamed shut, and the only option war drilling some new holes in the fridge chassis to make way for the temp probes and heating element. Also we had problem with fixing the SSR’s on the back of the fridge, as it was all insulation foam.
So we decided to take the project in another direction, and created a “Control Header” on top of the fridge.

In this way we have full control of the SSR, BPi and RPi wiring and function. The only wires going to the base of the fridge (beside the temp probes), are three 240V Neutral wires to/from the SSR’s.This also makes it easy to move the whole system to a new fridge if needed. All changes done to the fridge wiring system are done in a way so it can easily be reverted.

The internal thermostat in the fridge was disconnected, but the indoor light was kept connected and works as before.

Have done a test over a few days with a 25l conical fermenter filled with water, and it looks OK, but it does both overshoot and undershoot a bit more than I like., I might need some help in doing some adjustments to the settings.
Also, we are using a 200W element as a heater, it might be too big, as we see temp rise for quite some time after heating have stopped??

Looking forward to brew lager all year round, but also to see how accurate the system will work in “production”.
Here’s an internal look with 2x 25l buckets…

Any questions related to the build, just ask,…

Very Nice! I like the wood work you done and how you placed your BrewPi on it.

Hi JoeJr.
Thanks for you reply. Well, the stand is a bit bigger than necesarry, but works OK. The BrewPi are just mounted with velcro, and the RPi sits on a rubber mat in in a “pit”.
As I have no brew going on now, I am testing the temp inside the fridge i different ranges. I placed a12l keg for carbonation into the fridge and dropped to 4.5 C(Fridge Constant).

The fridge probe are mounted in the middle of the fridge, and I dropped the Beer probe down at the bottom. I saw about 0.6 deg between the two. Then I changed the fan direction, and now it differs only by 0.1-0.2 deg :smile:
1.In the first section, the probes are next to each other.
2. Here I dropped the beer probe to the bottom.
3.Turned the fan of.
4. Here I reverted the fan’s direction (now blowing downwards)

Still worried that my heating element are to big ; 200W. Any comments ?

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Looks nice. Do you use a JULA Frostvakt. If so, i am doing the same. It should be fine in its lowest setting.

You are able to check out our build @ https://www.facebook.com/SollidensBrewery/

The bigger heater should be no problem at all with the new PWM support in 0.4.0. I’m curious how your chart will look with that.

Hi Elco,
Did the upgrade to 0.4.0 today, and here’s the first few hours.

Quite impressive,.:smile:
I had not yet got my head around the old algorithm, so here’s a question about the new one.
I am now running in FridgeConstant Mode, and I see that there are a 20 min interval for the cooler.
I also see that the time the cooler are active, differs. It started with 2 min active time, then 4 > 6, and now i think it have adjusted to about 5 min. What in the algorithm are doing this when in Fridge Const ??
I also did a change for the: Cooler derivative time constant (Td) It was default set to 60, and your recommendation was 0 when using for fermentation, right ?

Looks great now, and looking forward to my first brew :slight_smile:

I think the cooler is okay at 60. When the fridge sensor is in the beer, I would set it to zero. When used to measure fridge air temperature, I think 60 is okay.

What you saw was the integrator increasing to adjust for the losses to the environment at this temperature. The temperature was too high for a while, so the integrator increased until it balanced around the setpoint.

Hi TomA

Awesome build!

Are you based in Norway?

I am Norwegian and about to embark on a similar build this week. So I am wondering where you got the heater from.

Hi alvinalexander,
Yes, norwegian based in Norway (Porsgrunn)
Thanks for your response.
Heater purchased at Biltema, but you get the same also at Jula.