Customers often ask if boiler size matters. The answer is yes and no! Hopefully in this article you will understand what the boiler does and why the size of it matters for your coffee needs.
Boilers in espresso machines vary in construction material, size and assembly. Most are brass and some are stainless steel. The benefit of a stainless steel boiler is it will never rust, but by the time a brass boiler rusts out of a machine, it has probably been working long enough for the machine to have already paid for itself from production. All boilers are subject to lime and mineral build-up.
The size of a boiler can be important. With a large capacity boiler and a small wattage heating element, the machine will take longer to heat up and struggle to maintain its optimum temperature in a high volume output environment. The variables of wattage, voltage and boiler capacity are vast and can be confusing. Keep in mind it is valuable to have about 300 watts per boiler liter capacity for a 220 volt machine.
The most prevalent boilers on the market use a heat exchanger to supply water to the group head(s). Heat exchangers are essentially boilers inside of a boiler. The room temperature heat of the water and steam inside the main boiler heats up the cool water coming into the heat exchanger. What this means is that the temperature of the water is dependent on the amount of steam pressure in the boiler. If you increase the steam pressure, you are also increasing the temperature of the water being dispensed out of the group.
Some machines come manufactured with more than 1 boiler (dual-boiler) - one boiler is for steam and one for brewing. The perk of this is the ability to adjust either boiler to your specific needs. Each boiler has a different circuit controlling its heating element, and can be adjusted for the desired temperature of brewing and steaming.
Important: Check the water level. An empty boiler will burn out the heating element.
So - does boiler size matter? It does but it's not the only factor to consider when making your purchase. Voltage and Wattage are also important factors. The larger boilers have the capacity for more steam to be ready and less temperature drop in between shots compared to a smaller boiler. Remember, a larger boiler size also gives you faster recovery between drinks.