You see it all the time when reading about espresso machines, these three terms refer to the part of the machine that is tasked with heating up the water to the appropriate temperature for coffee extraction and/or milk frothing.
Despite the name, it rarely boils water. The name comes from old espresso machines, where the boiler was a big chamber, in many cases, most of the space was taken up by it, where water was kept at boiling temperature in order to keep a constant flow of steam and hot water going.
Nowadays, the boiler is a rather small chamber where water is heated up very quickly. But since we don’t boil water anymore, the temperature has to change every time you use it for steam. This usually means an inconvenient waiting time or a dripping steam wand.
These are the types of boilers found in today’s espresso machines:
Meaning that your espresso machine will have only one boiler to be divided between hot water and steam. This system is the most inefficient, particularly if you plan on depending on it for big workloads or quick successions of drinks that require steaming.
A single-boiler machine is always cheaper, and although not the best option, it will perform fine for casual use and home espresso machines.
The Heat Exchanger system functions by using only one boiler. The boiler is connected to the grouphead with a special tube which allows the water to reach the optimal temperature for extraction while flowing. This way, while the water is out of the boiler and on its way to the grouphead, the boiler is free to keep heating the water up for steaming. This means that by the time your coffee is extracted, you can get as much steam as you want!
Heat Exchanger systems are very efficient and fit into just about any type of machine.
Two minds think better than one. Conversely, two boilers are better than just one. To bypass any problem that might arise from having one single boiler, this system works by having two separate boilers: One for the water, and one for the steam. This way, temperature is always kept exactly how it should be.
Dual-boiler systems take up more space and are more expensive, but are by far more efficient and make better coffee -and steam- than the other heating systems. A must-have for commercial machines.
And that just about sums up each type of boiler system, free of technical jargon and other technicalities. Choose wisely!
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