Using the ACS Minima Espresso Machine

For those interested in a new espresso machine, there is no shortage of exotic masterpieces available for purchase. Assuming the budget allows, it makes for a quite a conundrum for an aficionado. What machine and why? What is most important to you? Function? Aesthetic? Reliability?

This was the dilemma I was faced with after deciding to replace a second espresso machine I have. While my Vesuvius by Advanced Coffee Solutions (ACS) has been my primary espresso machine for nearly 7 years, I made due with an older heat exchanger-based Quick Mill Anita that mostly had duties as an espresso machine at a vacation home, and one that I’d take along for vacations with my wife and the in-laws. And yes, I can confirm that making your in-laws lattes every day is a good way to ingratiate your way into an extended family.

My Criteria

My use case, and the fact that it would not be my primary machine shaped my purchasing criteria. I simply wanted a PID-based dual boiler machine using an E61 brew head that was well-built, with a relatively small footprint. As much as I appreciate ridiculous levels of adjustment and customization, the goal here was simplicity, high quality, and consistency.

The Decision

Ultimately, I chose the ACS Minima for its clean but unique design and its technical specifications. Ordering it directly from ACS, I leaned heavily on my trust with them (thank you Maria and team), since they are the manufacturer of the extremely well-built Vesuvius. I ordered it in a custom RAL color (7046) that is quite similar to a “Nardo Gray” on an Audi, and paired it with walnut knobs and portafilter handles. I think it turned out quite nice.

Now that I’ve had about 9 months using it, I thought I’d share a few thoughts on how it works, and how it compares to other units I’ve used. ACS most certainly had price points and other design constraints to abide by, so my comments will try to keep that in mind.

Observations

The first thing I noticed out of the box was that the heavy gauge steal used on the unit is quite noticeable, and terrific. The chassis looks and feels strong. As far as the size, while it is a dual boiler, it is about the same size, if not a bit smaller than my old Quick Mill machine. But as you can see from the photo below, it is noticeably smaller, and about 15kg or 33lbs lighter than the Vesuvius.

The controls are very simple. Two toggle switches and a dial pressure gauge, and that is pretty much it. Note that it does not have a brew lever, favoring a toggle switch instead. More on this in a moment.

To get familiar with the machine, I used my Femobook A68 single dose conical grinder. It produces the most consistent grind I’ve ever experienced with a conical. I’ve noticed the Minima requires a grind size about one click (8 microns) larger than the same 18g dose for the Vesuvius. This isn’t an unusual observation when comparing the Vesuvius to machines pushing water through at a flat 9 bar.

Heat up time is about what I expected. There aren’t many surprises for these styles of machines that have a lot of thermal mass, and similar heating elements. Depending on what you prefer, a reasonable warmup can occur in under 20 minutes but better to plan on 30 minutes or more.

The Minima uses a vibratory pump. These types of pumps used to annoy me with their noise, and seemingly inferior characteristics compared to rotary pumps. I’ve also been really spoiled with the supreme control of them magnetic gear pump in the Vesuvius. But I’ve grown to appreciate this little vibratory pump in the Minima. It is relatively quiet, and inherently robust. Most importantly, the slow onset of pressure with vibratory pumps is ideal for espresso – a characteristic overlooked with rotary pumps.

Digressing a bit, lets take a quick look at vibratory pumps and how they deliver a shot using a flat 9 bar of pressure versus a pressure profiled shot on a Vesuvius. The graph below shows the flow rate of a shot pulled on a Minima. I used an 18g dose to yield 36g on some home roasted beans from El Salvador roasted to around Fully City. First drip on the Minima comes in at about 9 seconds and hits a pretty steady but slightly increasing flow rate at about 20 seconds. The slight increase in flow rate of the last 15 seconds is due to the change in porousness of the puck.

Compare that to pressure profile of the Vesuvius, as shown below. The slow pre-infusion allows the first drip to occur at about 15 seconds, ramp up to full pressure, then pull back the pressure and flow rate for the last 15 seconds of the shot. This declining pressure aims to approximate what may be found in lever-based machines. Slightly off topic, but an interesting comparison nonetheless.

Steam power seems to be an afterthought on some machines, but not with the Minima. The combination of 2.3 liter steam boiler and a 2-hole steam tip will leave you with plenty of steaming power. I believe 2-hole steam tips can be a far more practical option where you may only be steaming perhaps 240ml/8oz. Less steam throughput equals a longer duration of steam velocity, which is a good thing. This unit comes with a traditional steam wand instead of the double-lined “no burn” style. You’ll likely only make the mistake of grabbing the wand at the wrong location once.

The cylindrical water reservoir can be removed quite easily, and isn’t electronically attached like the reservoir in the Vesuvius. This makes cleaning much easier, but can present another problem noted below.

Opportunities for Improvement

The Minima hits the mark in many ways, but there are a few items that could be improved. The good news is that many of these could be addressed in an updated model with relative ease.

The on/off toggle switch is identical to the brew toggle switch. I enjoy the simplicity and analog feel of these switches, but it is way too easy to shut the machine off when you intend to pull a shot. A quick fix to this would be to use a different switch on perhaps the power switch, or relocate it.

I will admit the drip tray is a little cumbersome. It is shallow, and do I do find a peculiar amount of water on the chassis below the drip tray even when inserted fully. This is probably from the steam wand being set so high making purging of water difficult. I do find it interesting how many manufacturers find drip trays so difficult given an otherwise great design. But alas, it is just a tray, and it works fine.

The low-water shutoff can sometimes prevent a shot being from being pulled with a reservoir that is nearly half full. I suspect this is an issue with their float sensors that don’t rest in the reservoir correctly. It would be nice if this detection was more precise.

The programmability and the use of a seven-segment LED display feels a bit dated. While ACS could have gone with something more sophisticated, I do understand why they kept it simple. The good news is that once it is set, there is very little need to change it.

Summary

The Minima is a delightful little machine. It works great, and is a solid purchase for anyone looking for a well-built, dual boiler machine that has a relatively small footprint.