Heat Exchangers Vs. Dual Boilers

Your espresso machine is one of the most important purchases you can make for your café or coffee shop. These are machines that are built to last decades, so it’s important that you work to ensure that your machine is fit for the task of handling your customer load. One of the major elements of every espresso machine is how the boiler works. This is a passing curiosity for home machines, as most boiler types will do the job in a home setting. On the commercial side though, boiler type can make a huge difference in recovery, and prep time. The type of boiler in your machine can also add to greater consistency from shot to shot, easing the load on you baristas.

The goal of this article is to help you understand the differences between heat exchanger type boilers and dual boiler systems. Each design is useful and valid, but with a bit of help from SCG you can make sure you purchase a machine with a boiler that will perform best for your shop. This is also an important topic for those commercial customers who have seen a lot of growth and are considering an upgrade or a second machine. It’s important to weigh where you’re at vs. the investment, because it can be a costly mistake to jump into an additional machine if you don’t truly need the capacity.

Heat Exchangers

The first thing to cover is what a heat exchanger actually is. To put it as simply as possible, this is a boiler that transfers heat from one fluid to another without those fluids coming into contact. To visualize this, imagine a pool of water with a tube running through it. The water in the pool will influence the temperature of the water in the tube, and vice versa, despite the tube’s material separating them. These types of boilers are used for thousands of home, commercial, and industrial applications. There is a good chance that you have at least one heat exchanger in your home, whether it’s your water heater, coffee machine, or some other appliance!

But how is this principle applied to an espresso machine, and what does it mean for machine performance?

In an espresso machine, heat exchanger boilers differ from standard boilers because of how they heat and control the water. Where a standard boiler pulls water directly from the boiler to both steam and brew, heat exchangers separate this process. This matters because the difference in water temp for steaming and brewing is over 40 degrees fahrenheit. That means you’ll have to wait for temperature changes between brewing and steaming. All of this is why the vast majority of commercial machines are a heat exchanger or dual boiler.

In a heat exchanger, brew water is pulled through a copper pipe that runs through the boiler. These tubes are designed to pull the water at the ideal temperature for brewing, guaranteeing the perfect water temperature every time. This is done by calibrating the pipe’s diameter and size to ensure that water passing through is heated to the correct temp as it runes through the pipe (and therefore through the boiler). Meanwhile, steam is pulled directly from the boiler, allowing you to brew and steam at the same time.

The trade-off here is consistency and specific temps for volume and finer temp control for each process in a dual boiler. These machines are also often more affordable than dual boilers because they just have a lower material cost to produce.

The downside is that it is possible to outrun them in very high volume scenarios, specifically when doing lots of steaming, and brew temps (and because of this, espresso flavor) can be less consistent in these situations as well due to fluctuations in temperature. While this can be true of a dual boiler as well, it’s less likely to run into inconsistencies in brew quality since the brewing is handled by a completely separate boiler and heating element.

Dual Boilers

Dual boiler machines are just what they sound like, machines with multiple boilers. Instead of a single boiler with multiple water paths, dual boilers just feature separate brew and steam boilers. This allows a boiler to be ready at all times for either task. The upshot here is the removal of temperature as a cause for shot inconsistency. It’s nearly impossible for a barista’s shot prep to outrun brew boiler recovery on a machine like this. Like a heat exchanger, a dual boiler allows you to steam and brew at the same time. Both boilers are temp stable at the required temp for each process, providing excellent consistency in both brewing and steaming. The only time this can change is, again, in high steam volume situations, such as trying to steam milk for 10 20oz. lattes in a row. The difference with a dual boiler is that this situation won’t cause brew temps to fluctuate and create inconsistent espresso.

So what’s the issue? The first, as you might have guessed, is cost. Machines with dual boilers tend to be much more expensive than heat exchangers because they pack in much more material. Functionally, a heat exchanger takes up the same amount of space as a single boiler. On the other hand, a dual boiler machine requires double the materials. That means double the components that could fail over time. They also requires double the space. This is another primary issue with dual boiler machines, they tend to run larger.

These caveats aside, dual boilers are powerful solutions for very high volume cafés, especially useful when you actually have multiple baristas working one espresso machine.

Which Is Right For Me?

This is going to depend on a lot of factors. First of all, there’s space and group count. Because of the way heat exchangers are designed, they make great single group machines when you’re pressed for space. A barista can work on them to pull a shot and steam at the same time, and they can be used with very little recovery time.

On the flip-side, a dual boiler machine is great for the cafe seeing volume that their current machine(s) can’t keep up with. A two group, dual boiler machine can effectively double your capacity. With this type of machine you could have two baristas brewing and steaming at once, solving speed issues you might be experiencing. They are also more precise than heat exchangers because of the dedicated boiler. Finally, if the brew boiler fails for whatever reason, you still have a boiler for steaming, or vice versa.

All of this can make the extra expense for a dual boiler machine very worth it. While heat exchangers can be hard to outrun, it is possible in high volume scenarios, especially when you’re making lots of milk drinks. Dual boilers almost completely alleviate this issue. Additionally, a dual boiler machine will offer a lot more “nice to haves” as standards. Things like fully saturated brew groups, dual PID controllers, steam check valves, and other higher end features.

As with all of these decisions, our commercial experts are happy to help you make a choice, so give us a call for a detailed consultation!

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