Flow and pressure profiling is a big deal in the espresso world now. There are lots of machines that do it, but they are all well over $1000. I have a perfectly good Bezzera BZ10, and the dimmer mod promises to give me flow control for roughly $20 out of pocket…and it’s fully reversible if I don’t like it.
So, rather than laying out several thousand dollars for a new espresso machine I decided to try my hand at the dimmer mod. I’ve had this machine for more than 10 years now and the only maintenance I’ve had to perform is regular descaling, replacing the group head gasket once, and replacing the Ulka pump once. The machine has been a really solid workhorse. So, why not try…right?
I’m not going to bore you with the details of performing the mod. You can look that up on YouTube – there’s tons of examples. Instead, I’m going to let you know about some gotchas and a few things I found interesting.
Not All Dimmers Are Created Equal
A cheap dimmer from the hardware store will NOT work on all machines (sorry Lance.) I tried this first, and my Bezzera BZ10 would not reach full pressure with the dimmer wide open. I spent a while thinking I wired it wrong, then I looked it up.
What I learned is that most of the dimmers sold to control lights use what is called a Triac circuit. The dashed line is the full waveform, and the square is what a Triac does. This circuit, even at full open, clips the waveform and doesn’t deliver the full power. Also, the usable throw of the knob was small.
Which Dimmer to Choose
The dimmer I selected was the HiLetgo Adjustable dimmer. This dimmer has a small adjustment screw that allows you to fine tune the range of the dimmer and has a range of 50-220V. With this installed, at full open, the pump reaches full pressure without issue. Withe the adjustment screw, I was able to set it so the usable range was the entire throw of the knob. That means I was able to set “0” to what I wanted…which was NOT full off…but just a slight trickle.
Wiring
It truly doesn’t matter which wire you pull. I tried both just for fun, and it really doesn’t matter, so just pull the one that is easiest to access.
You will want extra wire – cut it longer than you think to start…you can always trim it later. And, spade connectors with covers are nice given you are going to be operating around water. In the case of the Bezzera, the bottom of the frame is perforated (probably to ensure water doesn’t pool in the electronics. I routed the wires down and out two of the holes and used spade connectors there so I can quick-disconnect the entire thing if I want without opening the machine again.
Once installed, tuning is a simple process. Turn the main knob all the way to the “off” position and then turn on the brew switch. Adjust the small screw until you hear the pump start humming (clockwise will give more baseline power, and counter-clockwise cuts power.)
To test that you are getting full power, lock in a portafilter with a blind basket and turn on the pump to full power and check your pressure gauge. If the machine you are using doesn’t have a pressure gauge, well…you’ll just have to guess.
Mounting and Final Thoughts
This dimmer module has no case, so you will also want to either 3-d print something, or wrap it in some way…an open circuit board carrying full mains power through it is dangerous. That said…I’m living dangerously.
I used thick double-sided tape to secure the module to the frame of the Bezzera below the drip tray. I placed it here for 2 reasons.
It’s hard to access unless you are intentionally moving it. Because this module controls the power to the pump, there is a risk of it being left in the “off” position when the boiler needs to be filled. I don’t want someone bumping it accidentally.
The frame in this location is separate from the drip tray, and also separate from the case – so when I want/need to take it apart again, it will be easy.
So, this is installed, and it works. But, now I have to learn to use it. Each coffee will want slightly different settings, and some may not need this at all. Am I glad I did it. Yes.