Are you about to buy a new espresso machine and wondering what the differences are between a single-circuit espresso machine and a two-circuit espresso machine? Then you are at the right spot. We will explain to you in this article and give you a few tips for buying your new single-circuit or two-circuit portafilter machine.
As you probably know, the preparation of espresso is a highly sensitive process. In addition to many other factors, the right brewing temperature is also responsible for whether an espresso tastes good or not. All manufacturers are therefore trying to develop their machines in such a way that they deliver the correct brewing temperature for espresso extraction.
The more expensive the machine, the greater the technical effort required to keep the brewing temperature as constant as possible – especially when several espressos are extracted one after the other. The cheaper the machine, the greater the temperature fluctuations in the brewing temperature can be.
We will introduce both systems to you in more detail below.
Single circuit espresso machines
The simplest and cheapest system is the single circuit. The temperature is controlled here via a pressure switch. The heating element is switched on or off depending on the pressure inside the boiler. This results in temperature fluctuations of up to eight degrees Celsius when brewing espresso, which is enormous.
In a single circle, there is a water cycle – hence the name “single circle” comes from. In this one water circuit, the temperature must be adjusted by heating or cooling to achieve the best result for drawing off espresso or producing steam.
(source: own illustration based on the graphic from the book “Faszination Espressomaschine” by Dimitrios Tsantidis p. 121)
The ideal brewing temperature for an espresso is between 88 degrees Celsius and 96 degrees Celsius. The temperature of the water for generating water vapor, on the other hand, has to be significantly higher (between 110 degrees Celsius and 130 degrees Celsius).
The temperatures are regulated through the use of different thermostats, which are switched into the heating circuit as controls.
In single-circuit espresso machines, the water heated in the kettle is used both to prepare the espresso and to generate the steam to froth the milk.
In practice, it looks like this when preparing milk-based beverages such as cappuccino or flat white: The water in the kettle must be heated immediately after the espresso has been brewed. This is usually done by flipping a switch or pressing a button. Unfortunately, you have to plan a short waiting time until the water in the boiler has reached the right temperature for the production of steam. The frothing of milk with a single circle is, therefore, more of an emergency solution.
The single-circle Rancilio Silvia delivers great milk foam quality. Here you can find an offer at amazon.com
Would you like to find out more about espresso machines? Then we recommend you read our extensive espresso machine review.
Design-related problem with Single-circuit machines
If you want to extract another espresso immediately after frothing the milk, the temperature in the kettle must be lowered again. Because you don’t want water at 110-130 degrees Celsius to burn the ground coffee in the portafilter, do you? If espresso is brewed with water that is too hot, the espresso tastes extremely bitter and is also poorly digestible.
The cooling of the water circuit for drawing off another espresso is again associated with waiting time. Most of the single circuit units have no display for the current temperature of the water in the boiler. So you never know exactly when the machine has reached the optimal temperature for espresso extraction.
The boiler water can easily have a range of possible temperatures that can be up to 10 degrees Celsius and more. The temperature is different each time espresso is brewed, which means that consistently high espresso quality is very difficult to reproduce. An espresso that just tasted heavenly can just be terrible the next time it is consumed.
Temperature surfing with Single Circle
You can bring about a solution to the problem through “temperature surfing”. Temperature surfing is a method used to influence the brewing temperature in single-circuit espresso machines.
In practice it looks like this: Before each espresso brewing, you make an empty brew (empty brew = let water out of the brewing group) until the temperature in the kettle drops so far that the heating starts up again – the machine then makes a faint clicking noise and / or signals the heating process via a control lamp.
Then you wait until the heating switches off again (another clicking noise or the control lamp goes out). This is exactly the point in time at which your single circle has reached a reproducible brewing temperature.
If the temperature is now right for your taste and the espresso beans you are using, you can start the process straight away. If the water is still too hot, you will have to wait a certain time for the machine to cool down further. If the water is too cold, you have to heat the machine further using the switch for steam generation.
Without question: temperature surfing is something for espresso enthusiasts who like to experiment. But it works and you can get the most out of the respective espresso beans with single-circuit espresso machines.
Advantages of Single Circle
- Relatively cheap to buy
- Compact design (saves space in the kitchen)
- Good espresso quality when the temperature is optimal
- Short heat-up time
Disadvantages of Single Circle
- Small boiler
- High-temperature fluctuations
- Temperature management is necessary
- The preparation of milk-based drinks is cumbersome
- It is not possible to prepare espresso and milk foam at the same time
Examples of single circuit espresso machines
Conclusion on single-circuit espresso machines
Single-circuit machines are generally a good choice for anyone who only wants to draw espresso with a portafilter machine. Single-circuit espresso machines are cheaper than double-circuit espresso machines and deliver very decent espresso quality.
If, on the other hand, you want to regularly prepare milk drinks for more than two people with a single circle, you will most likely not be happy with a single circle. The waiting time for the water in the boiler to heat up or cool down can be a bit annoying. In our opinion, single-circle machines are therefore suitable for pure espresso drinkers who only occasionally need steam to froth milk.
Dual circuit espresso machines
Dual circuits are espresso machines that have two water circuits at different temperatures: One water circuit for the production of steam for frothing milk, and a second water circuit for the brewing water that is required for making espresso.
With the help of these two water circuits, you can prepare espresso and froth milk at the same time. Compared to single-circuit espresso machines, this is probably the decisive difference and a great advantage.
The system is designed as follows: A large boiler is built into two circuits, in which water is heated to between 110 and 130 degrees Celsius. This water is used to draw off hot water and to produce steam to froth the milk. A small water chamber, a kind of pipe, is embedded in this boiler. This is the so-called heat exchanger. In the Anglo-American language area, two-circuit systems are therefore also known as “heat exchangers” (HX).
(Source: Own illustration based on the graphic from the book “Faszination Espresso Machine” by Dimitrios Tsantidis p. 129)
The heat exchanger takes on a central function in two-circuit systems: When making espresso, cold water is pumped from the water tank or the fixed water connection through the heat exchanger located in the much hotter steam boiler. The water is heated to the desired brewing temperature. The heat exchanger is designed in such a way that the water stays in the heat exchanger at the best possible flow rate until it has reached the right brewing temperature (88 ° – 96 ° C).
However, two-circuit espresso machines have a small weak point: If the machine is switched on for too long after espresso has been brewed, the water in the water chamber of the heat exchanger gradually takes on the boiler temperature. And that is way too hot to draw off an espresso.
Therefore, if the machine is switched on for a longer period, you should drain the water before the next use until it no longer comes out of the brewing group in a steamy manner (“cooling flush”). This means you can be sure that the water has been completely drained from the heat exchanger. In specialist circles, this process is also called the empty reference.
Advantages of dual circuit
- Espresso and milk foam can be prepared at the same time (no waiting time required)
- Relatively high-temperature constancy
- Lots of steam power
- Very good quality espresso and milk foam
Disadvantages of dual circuit
- Expensive to buy
- Less compact in design
- “Cooling flush” required
- Unsuitable for large parties or in gastronomy (steam pressure and brewing water temperature cannot withstand this)
- Longer heating-up time
The Bezzera Magica is a great two-circuit espresso machine. Here you can find an offer at amazon.com
Conclusion on two-circuit espresso machines
If you want to prepare a lot of coffee and milk beverages with your new portafilter machine, then we recommend buying a two-circuit machine. You can froth the milk while preparing the espresso. The large two-circuit boiler provides plenty of steam power for frothing milk. The preparation of cappuccino & Co. is a real pleasure. And in our opinion, that makes a two-circle better than a single-circle.
Buying a dual circuit is an expensive affair: prices start here from around $ 1,185. With a bit of luck, you can buy used two-circuit vehicles for less than $ 1,000.
Examples of two-circuit espresso machines
Differences between single-circuit and two-circuit
For a better overview, we have created a table with which you can see the differences between single-circle and double-circle at a glance.
|SINGLE CIRCLE||DUAL CIRCUIT|
|Number of water circuits||1||2|
|Prepare espresso and milk foam at the same time||No||Yes|
|Espresso quality||Good||very well|
|Milk foam quality||good, but depending on the model||very well|
|Suitable for beginners||yes (with a few restrictions)||Yes|
|Suitable for gastronomy||No||limited|