The Boiler: What's Under the Hood
When you're talking espresso machines, there are a few things that usually come up in casual conversation – style, capability, super, semi or lever. Rarely does the boiler come into play. But if and when it does, you should know what you've got under the hood.
Double or Dual Boilers
Lucky enough to own an Expobar Brewtus II? It's one of the best semi-automatic machines on the market, certainly one of the most durable. That's because of its commercial design, with double or dual boilers as they're called. A double or dual boiler system has its own dedicated 975-watt heating unit, which makes it possible for the boiler to run at a precise temperature. This type of boiler system guarantees a consistent temperature, providing you with unwavering temperature stability.
Double or dual boilers also mean that there's no switching boiler temperatures as you go back and forth between steaming and brewing. Because each boiler is set to the correct temperature for its function, there's never any wait time for the boiler to cool off, or heat up. Double or dual boilers make it possible to brew and steam simultaneously, which is perfect if you're making a few drinks at the same time, or if two people are working on the same machine.
And because the boilers are so large, and automatically draw water from the reservoir on their own accord, you'll eliminate any wait time between shots because you never run out of water or need the water to get up to temperature. While this pro-sumer machine was built to commercial standards, the engineers at Expobar did take into account the standard 15-amp household breaker, so you'll never blow a fuse.
Heat Exchanger Boiler
The Pasquini Livia 90 and the Expobar Pulser are shining examples of how well a Heat Exchanger Boiler functions in a home environment. Built with an enormous 1.5 liter copper boiler, the Livia 90 will heat up in less than ten minutes. The Heat Exchanger Boiler works like this – the boiler itself has a pipe that runs through it, which is aptly named the heat exchanger. That pipe is strictly dedicated to brewing. Water will pass through the exchanger from the pump, while the water that's in the boiler itself provides the steam.
Heat exchange boilers always have steam in them, so there is never a wait time to switch from brewing to steaming. This is the greatest benefit of heat exchanger machines. The other benefit is that fresh water is always being used, as opposed to reheated water, as in a single boiler machine.
Heat Exchanger boilers also have water level regulators that are connected to the sensor in the boiler. The regulator monitors the water level with the aid of an electronic boiler refill control. Probes mounted inside the boiler will sense the water levels as they fluctuate, and will turn the boiler off if the reservoir or boiler runs out of water. This system, in its entirety, will protect the heating element so you'll never burn out your machine.
Rapid Steam System
Allowing you to easily switch back and forth between brewing and steam, the Rapid Steam System is unique unto itself. Since it's a separate heat exchange system, and separate from the traditional boiler, it enables you versatility when making multiple drinks like café lattes or cappuccinos.
By simply pressing a button on the control panel, you'll be able to produce full-strength steam because of the two systems, the brew boiler and rapid steam system, which are separate. The two systems enable you to switch back and forth between steaming without waiting up to 45 seconds like on single boiler machines.
The Rapid Steam System itself sits on its own plate internally (it looks similar to a horseshoe) but heats rapidly thanks in part to its own complex heating element. This innovative technology is found on many machines nowadays, like Saeco, Bosch, Jura-Capresso and Gaggia.
Many entry level, home espresso machines feature a single boiler. These machines typically have one boiler with two thermostats that regulate the temperature for brewing and steaming. When brewing, the boiler will heat the water to a certain temperature, then, when it's switched to steam, it will heat up even more to reach steam temperature.
The benefit of a single boiler machine is that it brews quality espresso to be at a lower price point. FrancisFrancis! machines hold large amounts of water, capable of making 16 two-ounce cups. Many of these boilers are made of brass, while the insides are usually lined with aluminum. On the FrancisFrancis! machines there is an automatic refill function, so as long as water is in the reservoir, the boiler will pull water and never run dry. This is a great feature, especially if the machine is left on for a prolonged period of time, as the boiler would normally run dry and result in serious damage. We of course, never advise you to leave your machine on when not in use.
Hopefully this guide has given you a better idea of what the types of boilers are out there. It's good to keep in mind how often you'll be entertaining friends when you start comparing boilers. Double or dual boilers eliminate the wait time between brewing and steaming, which proves extremely helpful when you're making five lattes after a dinner party. A single boiler will take up to a minute to vent excess water and cool down between steaming and brewing, but if that's not a big deal and price is a concern, a machine with a single boiler is the choice for you. It's always good to know if you've got a Hemi under the hood or just a straight-5.