How to Choose a Heat Exchanger Machine
What is a heat exchanger?
A heat exchanger (also referred to as HX) is an espresso machine with a single boiler that is dedicated to steaming milk. Rather than having a second boiler dedicated to brewing (a dual boiler) or using one boiler for both steaming and brewing (a single boiler), it has a coil attached to the boiler that rapidly heats water as it passes through. When the machine is on and idle, the water in the coil gets very hot and must be flushed before pulling a shot. This is why we recommend a “cooling flush” before pulling a shot on an HX — the boiler is dedicated to steaming and sitting around 250 - 270 degrees Fahrenheit.
Photo: Bezzera BZ10 Espresso Machine and Eureka Silenzio Espresso Grinder
What are the advantages and disadvantages of having an HX machine?
Heat exchangers are often used in commercial settings as they have lots of steaming power, the ability to make a ton of drinks back to back, and can simultaneously steam milk while pulling a shot. An advantage to having one in the home is its ability to pack the power of a dual boiler machine into a smaller footprint.
Most heat exchange machines don’t provide a way to control brewing temperature to one degree, which is seen as a disadvantage for many baristas. However, heat exchange machines are guaranteed to brew in a suitable range for espresso to ensure the coffee is extracted properly. Standard HX machines temperature surf, which means the boiler will bounce between its lowest and highest setting to stay in the range. This can be seen as a negative as you’re not guaranteed a specific brew temperature. However, the water will never be too hot or cold for espresso, it just can’t get as precise as some baristas want. HX machines with PIDs like the Profitec Pro 500 and the LUCCA X58 have a PID, which is a digital interface that allows for temperature control. In an HX machine, this looks like controlling the steam temperature, which directly affects brewing temperature.
A few years back, we answered a commonly asked question, “Heat Exchangers with PIDs: Are They Worth it?”
The new Pro 400 from Profitec has a 3-position switch that controls the boiler's temperature, giving you a low, medium, and high setting that equates to about 194 degrees, 201 degrees, and 208 degrees. For most, this is enough option and control. For others who want to play with temperature as a way to change how a coffee extracts, this isn’t precise enough.
Photo: Profitec Pro 400 Espresso Machine and DF64 Espresso Grinder
Why does brewing temperature matter?
When making coffee, you need the perfect combination of grind size, time, and water temperature to pull all of the great flavors out of coffee— this is extraction. Brew time and water temperature can almost be interchangeable—for example, cold brew. To make cold brew, coffee grounds soak in room temperature for 24 hours. When you use hot water, you can extract much more quickly. Since espresso is such a quick brewing method, you need very hot water. The range for espresso is between 192 and 204 degrees. You’ve probably seen a variance in the range suggested by other coffee professionals. This is what works for us and is not a hard rule but generally, good guidelines to follow. Depending on the coffee you use and its roast level, it may need hotter or cooler water when brewing to ensure proper extraction and delicious result. As you know, you can get pretty nerdy with coffee brewing. Changing temperature is one of those variables in making coffee that can be fun to mess with, but to new baristas and less experienced palates, results might not be noticeable in the cup.
You can read about how to use water temperature to play with coffee extraction and how to brew based on the roast level in our article How to Brew Light, Medium, and Dark Roasted Coffees.
If you don’t see yourself as someone who wants to mess around with brew temperature or is okay with less precise brew control, and you want something powerful, reliable, simple, and small, a heat exchanger is a great option. So how do you narrow it down?
Photo: LUCCA X58 Espresso Machine and Eureka Atom 75 Espresso Grinder
How do you choose between HX machines?
These machines generally do the same thing. They all have very similar internals— vibratory pumps, water reservoirs, and E61 group heads.
- Features. Do you want a PID or temperature control? Check out one of these three: Profitec Pro 500, LUCCA X58, Profitec Pro 400
- Budget. Our favorite budget pick is the Bezzera BZ10. It’s super compact and sits right around $1600.
- Aesthetics/Brand. Here, we choose the ECM Mechanika V Slim. It’s the smallest HX machine with the most power and features stylish rotary valves.