Published : 01.03.2023 10:14:26
Categories : General
One of the most important features on an espresso machine is creating warm water. With the earliest espresso/coffee machines this was done with a open flame by burning natural gas. This principle was the only way of heating up the boiler. After the second world war the usage of heating elements started to become more common.
The usage of gas for heating up a espresso machine is still a option with some espresso machine manufacturers such as Astoria CMA and Rancilio. This is mainly done for espresso machines where no power outlets, or too little amperage is available.
First we start with the basic principles of a heating element, a standard tubular heating element is made up out of 7 components.
Figure 1 https://www.hotwatt.com/our-products/tubular-and-finned-tubular.html
The heating element tubing
The Heating element tubing is the outside of the heating element and can be used from various materials such as stainless steel and copper.
The element wire is the section of the heating element which produces the heat.
This electrical insulator around the element wire is made from Magnesium Oxide powder (MgO). This insulator prevents that the powered element wire comes in contact with the heating element outer tube.
This is the connection between the heating element thread and the cold zone/electric connecting rod.
The cold zone is the part of the heating element where no heating element filament is located. This can be done for various reasons.
This insulator is located between the outer tube material and the inner wire. This prevents that the post terminal/cold pin could short out between the outer tube. With a 230/380V heating element these are almost always white. For 110V heating elements, these are in most cases, coloured in a red colour.
The post terminal/electrical connection
This is where the electrical power supplied is connected to, this can be in various types such as threads or spade connectors.
The heating elements used on espresso machines are numerous of shapes and sizes of heating elements made throughout the years and you see that various brands also have their own design of elements. What kind of various features are there?
There are 3 types of heating element flange. There is a screw in, a bolt on and a boiler flange model. The screw in model are more common with the domestic/prosumer espresso machines and with some commercial brands as well. The least type of model is where the heating element flange is also the flange of the boiler
Screw in heating element.
This type of heating element is fitted with a threaded flange. This threaded flange can be screwed into the boiler itself. The most common sizes are a 1” and a 1”1/4. These types of heating elements can be found on brands such as Astoria, Vibiemme, Wega, La Marzocco, Rocket, ECM Heidelberg and Bezzera.
Bolt on heating element
This type of heating element is the most common style of heating element flange. The flanges are in most cases made from casted brass and held in place with bolts. This does vary with every brand. They go from 2 bolts all the way up to 6 bolts to close of the boiler flange.
These flanges can be made from either casted brass/stainless or pressed stainless steel sheets what you see nowadays more often. Seen it is less expensive.
The flanges can also have a variety of shapes. These range from triangular, round, oval and various brands which use their own design of flange.
Below you will find a schematic overview of flange models which are commonly used on espresso machines. Note: This is only an overview of the shapes which are used on espresso machine brands, this does not mean that they are compatible.
Heating element boiler/flange
In some cases the heating element is a integral part of a espresso machine boiler and can’t be removed. In this situation you have 2 categories. Boiler with heating element and a boiler flange with heating element. In both cases the heating elements are fixed to the other parts and can’t be changed out.
The heating element as a integral boiler component can be found on brands such as Gaggia, Nuova Simonelli and Victoria Arduino.
The flange heating elements are more common with some brands. A good example of this type of heating element is the heating element used on the La Pavoni Europiccola/Professional espresso machines. Where the heating element is also the boiler flange at the bottom of the boiler. Other brands where you see this type of heating elements are La Spaziale, Bezzera and Elektra.
Cartridge heating element
This type of heating element is not used to heat up water in a boiler, but to keep the brewing group body at a certain temperature. These heating elements go at the low range at 150W and at the high range around 800W. You will find these types of heating elements on Nuova Simonelli, Astoria, Wega, La Marzocco, Grimac, Bezzera, San Remo and Victoria Arduino
A heating element can be specifically made for a voltage, for instance 110V/230V/380. The 110V heating elements can mainly be found in North America and in Japan. In the rest of the world it is quite uncommon nowadays to find that voltage. This used to be a different story when in some countries there was a combination of 100-110V and 200-220V.
The 230/380V heating elements are more common in the rest of the world. In most cases the heating elements are designated 230V, 230/380V or solely 380V.
The wattages range from the low range multi boilers and domestic espresso machines from about 800W all the way up to 4 group heating elements which produce around 6000W of power. The amount of wattage produces by the heating elements does depend on the length, cold pin length, effective heated area and the recommended wattage for the liquid(water) which needs to be heated.
The length of the heating element does depend on various factors. First off all, how long is the available space inside the boiler. The length of the boiler does also have effect on the wattage it can produce. There are 2 options with high wattage elements, short multi row coils or just ½ rows which is longer.
The material used traditionally, in the most cases, for the tubes is copper and for the flange is brass. These 2 materials are soldered together at the flange side. The recent years you see the usage of stainless steel for heating elements. In these cases the flange and the heating element tubes are made from stainless steel. You will find this various models of the brands such as La Spaziale, Faema, ECM Heidelberg, La Pavoni, San Marco and Casadio.
One of the reasons for the choice of stainless steel is that is that the material is cheaper then brass and copper. But also the higher temperature resistance. When a stainless steel heating element boils dry it does not deform/break down such as the traditional copper heating elements.
There are various styles of connector used on heating elements in espresso machines. There are 2 styles, the threaded and the spade connector.
The threaded connectors, as it says, nuts and washers which are screwed over the electric connection sticking out of the element tube. This assembly is normally made up out of a nut, 2 washers and a sealing nut. In-between these nuts you can install a round electrical connector. The nuts and washers used can range from a M4 thread up to a M6 connection. In most cases these washers and nuts are made from brass.
The other connector, which is less common, but can be mainly be found on single connector heating elements or with some brands for multi connectors such as Casadio, Faema and La Cimbali. These connectors are straight or placed at a 90 degree angle, they can not be removed seen they are welded to the electric connection. You can slide a 6,3mm female connector over these terminals.
Some heating elements have a spare hollow tube installed inside the heating element. This one is open at the flange side and closed/soldered at the water side. This spare tube is installed for a heating element thermostat. This thermostat is installed to prevent overheating of the heating element, once it has been overheated they are normally not usable anymore and need to be replaced.
Troubleshooting a heating element
It is possible that if your espresso machine doesn’t heat up anymore. If your heating element is broken this can be the case. But it is handy to look at the big picture, seen this can also be caused by other components in the espresso machine. First of all start with to turn off your espresso/coffee machine.
You can start first with checking your pressure switch and your heating element thermostat, if you have one installed on your espresso machine. in the case of the pressure switch, if your espresso machine is cold it needs to be in a closed position. So when you measure resistance it should give a reading of below 1(or 0). If it gives a reading of 1 the switch is open and it is likely that the switch needs replacing.
A other option is to check the heating element thermostat(or boiler thermostat). Because if that one is tripped the connection to the heating element is interrupted and your heating element won’t work either.
Test your heating element on continuity;
To test your heating element you require a multi meter to test the resistance of the coil. Hold one of the probes on one side of the electrical connection and one on the other side. You should get a reading of approx. of 0,02-0.12 ohm. This does depend on the voltage of heating element. But this means that there is a resistance on the heating element and that is ok. If you get the message 1 there is no resistance measured and the wire doesn’t have continuity.
Test your heating element on a short circuit;
When you have a short circuit in your espresso machine it is possible that this is cause by the heating element. If you want to test your heating element you need a multi meter to test continuity. Instead of continuity on 2 electrical connections you connect 1 pole to the electrical connection and you hold the other one to the flange body. When there is no short circuit on a heating element you will get a reading of 1, there is no flow of electricity. When there is a short circuit, you will get a reading from 0,01 up to 0,99. If you have this, you need to replace your heating element.