How to Choose a Prosumer Espresso Machine: Dual Boiler or Heat Exchange?

by Whole Latte Love December 21, 2018 10 min read


So, you’re super serious about your espresso and need a machine that reflects your passion. Maybe you’ve been limited by a finicky, entry-level single-boiler machine, or you're ready to jump right in with a very capable first machine.

Hey espresso lovers, Marc here from Whole Latte Love. Today I’ll cover what you need to know before you decide on a prosumer level machine that’s right for your needs. In this post, I will not be making hard machine recommendations. If you’d like to learn about our top machine picks, use this link for a video featuring our favorite semi-automatic choices.

What I’ve got are basic considerations and some inside knowledge about important features and the qualities of certain machines and manufacturers that, frankly, many current owners might not even know about.

  • For example, did you know that some machines can do line-pressure pre-infusion when plumbed-in and some cannot?
  • Do you know which brand makes a dual boiler machine that’s a thousand dollars less than the competition, yet, just as capable?
  • Do you know which manufacturer makes machines with best in-class steaming performance?
  • Finally, do you know why some users prefer vibration pumps over rotary pumps?

  • Well, stick with me and I’ll answer all those questions and a lot more.

    So at Whole Latte Love, we carry machines from about a dozen manufacturers and there’s plenty of machines from other manufacturers that we don’t. Why? Well, we offer an industry best three-year parts and labor warranty on all our prosumer level machines. So we are very selective in the machines we carry. These machines have to meet our high standards for quality and reliability. We visit manufacturer production facilities and we know their products inside and out. Our service center works on thousands of machines every year and every prosumer machine we ship goes through testing and setup by our factory certified techs before it gets to you.

    Now, if you’ve got questions before you purchase or need some help after, our coffee pros are just a phone call, chat, or email away. If you’d like to talk to a coffee pro, use the link for our contact info to get some free one-on-one advice. Of course, I can always help you out right here in the comments as well.

    Let’s get into the machines, what you need to know, and that insider knowledge.

    At the prosumer level we’re generally talking about machines with either a heat exchange boiler or dual boilers, full commercial size 58 mm portafilters, substantial groups, and robust construction.

    Looking at Heat Exchange Machines

    Rocket Mozzafiato Ceado Lifestyle

    Let’s cover boilers first. If you’ve ever made a latte using a single boiler machine, you know you can’t brew and steam at the same time. It’s a dual-use boiler, so you either brew your espresso first and then wait for the machine to heat up to steaming temperature, or steam your milk first and cool down the boiler to brewing temperature. With a heat exchange or dual boiler machine you can brew and steam at the same time. Not only does that save you time but it makes a better milk-based drink as your espresso or milk froth doesn’t fall apart while waiting for that temperature change.

    In a heat exchange boiler, it’s one big boiler with an isolated section within the boiler, supplying cooler water for brewing. In most cases, water constantly circulates via thermosiphon from the inner section out to the group head and back. That heats the group for temperature stability and cools the water within the inner section to a temperature appropriate for brewing. For controlling the temperature in the boiler, if you go back a few years, it was usually a pressurestat doing that. It measures the pressure within the boiler which equates to a temperature.

    In the last few years, more machines have started using PIDs to control temperature in HX boilers. PIDs are far more accurate than pressurestats. They use logic and very short pulses of energy to the heating element to eliminate the temperature swings. In a machine with a pressurestat in-boiler, temps can swing as much as five or ten degrees when the machine is sitting idle. Under PID control an HX boiler swings about one degree. Examples of machines with heat exchange boilers and PID control are the Profitec Pro 500 PID, Rocket Evo Rs, and Type Vs in the Giotto and Mozzafiatto models.

    Heat exchange machines using pressurestat-controlled temperature typically require a cooling flush prior to making espresso. The new crop of HX machines with PID do not. They produce accurate brew temps. Our scace testing shows manufacturers have done an outstanding job of engineering thermosiphon systems to avoid overheating brew water and produce accurate brew temps without flushing.

    Now, that said, some users may prefer a heat exchange machine with a pressurestat. On those, using a timed flush allows them to quickly adjust brew temps. A few seconds longer on the flush and you get a cooler brew temp. A few seconds shorter and you get a higher brew temp. One caveat there is that you really don’t know what the brew temp is. It’s an immediate change, but a bit of a guessing game. On a PID machine, it takes longer for a temperature change to fully stabilize as the thermosiphon equalizes the group. Personally I prefer PID. I know what the brew temp is, it’s repeatable, and the flushing on non-PID machines tends to fill up drip trays fast and I hate emptying drip trays.

    Pump Types and Groups in Heat Exchangers

    Beyond PIDs and pressurstats, the other major considerations on HX machines are pump type and group type. Pumps are either vibration or rotary. Vibration pumps are most common. There are only a few HX boiler machines with rotary pumps. Rotary pumps are considered commercial grade, but there’s nothing wrong with a vibration pump, in fact, some users prefer them as they ramp up to brew pressure more slowly than a rotary pump. The result is a short period of lower pressure pre-infusion prior to reaching full brewing pressure. Although not controllable, it may be beneficial and slightly reduce the chance of channeling during an extraction as the coffee has some time to swell up prior to full pressure brewing. On the downside, vibration pumps tend to be a little noisier and very few vibration pump machines are plumbable direct to a waterline, while most rotary pump machines are. Examples of HX machines with rotary pumps are Rocket Espresso’s PID equipped Evoluzione R Mozzafiato and Giotto machines.

    For group type, the E61 with thermosiphon is fairly standard. There are a few machines with electrically heated groups like Bezzera’s BZ10. Rather than relying on a flow of hot water from the boiler to heat the group, an embedded thermostat monitors the group temperature and heats it as needed. The main benefit is a group that’s up to temp in as little as ten minutes where an E61 group may require twenty minutes or more for full warm-up.

    So to recap HX boiler machines, your main considerations are temperature control. Do you want the no-flushing required accuracy of a PID machine? Or would you prefer the quick brew temperature changes using timed flushes on a pressurstat machine? Then pump type, most all HX machines use vibration pumps but there are a few like the Rocket Evo Rs which have a rotary pump. They’re a little quieter and are plumbable directly to a waterline. With groups, Thermosiphon E61 is the norm, but there are electrically heated groups like on some Bezzera machines for faster warm-up times.

    Dual Boiler Analysis

    Expobar Eureka Lifestyle

    Let’s get into dual boiler machines. At the start of the blog, I promised to tell you about one that’s every bit as capable as machines that run about a $!,000 more and it’s the Expobar Brewtus IV. Now beauty is in the eye of the beholder and there are machines with more refined external finishing, but if you are looking for the best value in a dual boiler: PID, rotary pump, and a plumbable machine, it’s the Brewtus IV-R. If you’re all about the value without compromising on performance, check out the Brewtus.

    The norms for dual boiler machines are rotary pumps, PID temp control, E61 groups, and of course the separate boilers. One makes steam and a second heats the brew water. With isolated boilers, brew temps are even more stable than on the PID heat exchange machines and you can adjust them faster. You typically get better steaming performance as well with a dedicated boiler and on many machines you can turn the steam boiler off if you’re just making espresso.

    Speaking of steam, I also mentioned I’d clue you in on machines with the best-in-class steaming performance, the Profitec Pro 600, Pro 700, and the ECM Synchronika. All three machines run the steam boiler at near 2 bar of steam pressure, in comparison to other dual boiler machines running at about 1.2 bar of pressure. That extra steam pressure is a big deal if milk drinks are your thing, as it puts commercial type power in your home or office.

    Finishing Touches

    Other differences come down to finish and features. While the Expobar Brewtus is built like a tank with some of the thickest metal found in a machine case, it’s somewhat utilitarian in design. As you go up in price you’ll get machines with refined edge work and extra detailed craftsmanship that makes a statement. Some machines use levers for steam and water valves while others use knobs.

    As for features, some machines have PID displays which change to shot timers when an extraction begins. Others hide or remove controls from the face of the machine to maintain a classic look with no digital displays, a common theme found on Rocket Espresso products. Bezzera’s dual boiler Matrix and Duo machines go the other way with touch screen panels used for all control, including boiler pressures, PID temps, auto on/off functions, and maintenance reminders. Their Matrix machine even has light up, adjustable color, clear side panels.

    One last thing to consider is what’s under the hood of these machines. It’s something we pay a lot of attention to. The quality of internal components and how they are engineered.

    All machines with an E61 group are capable of pre-wetting coffee in the portafilter prior to applying full brewing pressure. Just a few are capable of doing a pressure controlled pre-infusion when plumbed direct to a waterline. Among those are the Profitec Pro 700 and the ECM Synchronika. Raise the E61 lever to just before the pump comes on and whatever pressure is on the plumbed line is applied to the coffee. If you put a pressure regulator on the plumbed line you can dial in whatever pre-infusion pressure you like and if you’re an espresso geek, it’s a very cool and useful feature.

    So that wraps up our basic look at heat exchange and dual boiler machines. If you want to learn more about any prosumer level machine we carry just go to our product catalogue, find the machine, and chances are we’ve got an in-depth video review that’ll get you under the hood and cover all the machine’s features. I’m Marc, thanks for reading, and I hope you’ll come back soon for more of the best on everything coffee, brought to you by Whole Latte Love.

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