Synesso™ Commercial Espresso Machines
Designers notes
Temperature stability
It is generally accepted that espresso machines with coffee tanks that are separate from the steam tanks are more temperature stable than machines with a single tank and a heat exchanger system. A heat exchanger that is idle will increase in temperature to be close to the temperature of its heat source (the steam tank).
Most heat exchanger style machines will fluctuate their brewing temperatures by +/- 6° C. By using a dedicated steam tank, the steam tank temperature can be adjusted (this changes the steam pressure) without affecting the coffee brewing water temperature.
There are several variables that affect the brew water temperature in separate boiler machines. A machine with a single coffee tank and two or three brew groups will have different temperatures between the groups. It is common to have 0.8° C of drop from group to group, so a three-group machine can run the first group 1.6° C hotter than the third group. The Synesso Cyncra employs individual tanks for each brewing head that allows a precise setting of the brew water. Individual groups can be set to different temperatures, providing the ability to brew at the sweet spot for light and dark roasted coffee on the same machine (see Brew Temperatures and Coffee Roasts for details).
The brew group is heated by the water inside the shell of the group, it is important to the efficiency of the group to ensure that the wall thickness (the distance from the water to the outside of the group) does not vary. In the Cyncra groups, the wall thickness never exceeds 6mm, this ensures even temperature dispersion. This is especially important at the diffuser as its heat is closest to the coffee; it must be as close to the brew water temperature as possible.
Temperature control for the brewing water in one of the more stable two boiler machines is controlled with a snap switch driven by a mechanical thermostat. The way this thermostat works is by expanding and contracting the air inside of a bellows which is surrounded by oil in a tube. The tube is coated with thermally conductive grease and then inserted into a second tube that is in the coffee tank brew water. When the heating element is on, it heats the water which transfers heat to the outer tube, which heats the grease, the second tube and the oil in the thermostat. This expands the air in the bellows, which moves the piston that pushes against the pin on the snap switch. The switch then opens the contacts and turns off the heating element. The time required for this type of thermostat to switch on and off allows the water temperature to fluctuate above and below the set point by a minimum of 2.7° C. The Cyncra uses a probe that is able to sample the water temperature every second and turn on and off the element without delay.
The water that is added to the coffee tank when brewing affects the tank’s ability to stay at a stable temperature. In most machines when the water comes directly from a cold water line it will reduce the temperature in the tank as it replaces the water used to brew coffee. Some people will rinse a portafilter after brewing espresso; this introduces even more cold water. The coffee tank and brew head also cool naturally at a given rate based on the outside temperature and the surface area of the tank and brew head. The Cyncra uses a water preheat system from the steam tank that delivers the water to the brew tank at a temperature that is hotter than the water in the brew tank. The heat differential is enough to compensate for the heat loss from natural cooling. The use of a water preheater ensures that cold line water will never be directly introduced into the coffee tank.
It is important that coffee brew water is not given the chance to cool off on its way to the coffee grounds. Some machines rout the water out of the heat source in copper tubing, to flow meters and solenoid valves and then back into the heat source hoping that it will return to the desired temperature before it reaches the coffee to be brewed. The Synesso Cyncra uses all stainless steel internal tubing that never leaves the water saturated group; therefore, there is no change in the temperature during the water delivery process.
When evaluating thermal stability, keep in mind that the variables add up. Any one variable may make only a small difference; all of the variables together can add up to a machine that is surprisingly unstable. Testing stability needs to be done in the brewing process, with ground coffee and a probe placed at or slightly below the surface of the coffee grounds. The first pull from a machine that has been at rest for over 15 minutes is the first temperature that you should record. Continue to pull shots as quickly as possible until several readings are the same; this will be your stable brew temperature. With most espresso roasts, a total variable of 1.1° C can be tolerated without affecting the flavour development, however some roasts are more sensitive than others.
Brew temperatures and coffee roasts
The relationship between brew water temperature and degree of coffee roasted (how dark or how light the beans are) needs to be understood before selecting a brew water temperature for your espresso machine. As a general rule, espresso is brewed around 93° C to 95° C. This is a good place to start taste testing a medium roast coffee. Some very dark roast coffees can brew quite well at 89° C, while some very light roast coffees brew the best at or above 95.5° C. Look closely at the coffee you choose and if you see oils on the outside of the beans and the roast is medium brown, try lowering the temperature, if the beans have no oils on them, try raising the temperature. When you find the proper brewing temperature for your espresso, you will get the results in the cup that your customers want. It’s also important to note that altitude can also make a difference in the optimal temperature that a given coffee brews.
Brew temperatures in the Cyncra are easily changed by selecting the group that you want to change with the Zone button, then hold the Set button and push the Up or Down arrow to change the set point. When you release the Set button, the display will show the temperature in the tank at the brew water pick up point. There is also a light to indicate if the heating element is on or off. The light will flash on and off when the element is pulsing as it reaches the set point; this allows the element to cool off and not overheat the water. If the indicator light just stays on, the element is at full strength and heating the water as quickly as possible.
Pre-infusion, jetted flow or both
Pre-infusion is the low pressure wetting of the coffee grounds. This is done without the pump running and the purpose is to evenly moisten and swell the coffee grounds in the basket to provide the maximum resistance and an even flow of water through the coffee. The Cyncra has a two stage brew switch; the first position opens only the brew valve to allow the pre-infusion (using only line pressure) to take place and when you see a drip or two of coffee from the spout, push the switch to the second position to turn on the pump and brew at full pressure (normally between 8 and 9 Bar).
Jetted flow is the use of a flow restrictor in the brew water delivery system; this slows the flow of water to the ground coffee, allowing the coffee to become saturated slowly. If a flow restrictor is not used, you may see a surge of coffee at the beginning of the brew cycle. As the cycle progresses, the pour will slow to a normal flow because the coffee is swelling in the basket and creating more resistance. The Cyncra comes with a 0.6mm diameter flow restrictor.
The Cyncra gives the option of jetted flow, pre-infusion or both. The jet size can be changed or the jet can be removed if so desired. This does require a trained technician; however, it is a quick and inexpensive process.
Repetitive motion injuries
Repetitive motion injuries related to turning a steam knob are not an issue with the Synesso Cyncra, the steam is actuated with a lever that is drawn forward, it moves easily and will stay where it is moved, providing the operator with infinitely adjustable steam pressure.
Machine durability and reliability
All of the tubing used for water delivery to coffee tanks is 300 series stainless steel; it is extremely durable and sanitary.
Solid state relays are used to control the heating elements. The Cyncra has no mechanical relays driving heating elements, oil filled thermostats, or rubber diaphragm driven pressure switches.
The only rubber used in the Cyncra is found in the solenoid valves, and other control valves, there are no gaskets made of rubber. The heating element gaskets and water drain and inlet gaskets are made from Teflon, the same material used for most high heat and steam applications. It is extremely durable and can be reused several times.
The heating elements are stainless steel; they can heat in the air to 760° C without damage to the element. The maximum temperature for an element made from copper is 176.5° C.
There is no use of mild or carbon steel so there shouldn’t be any possibility of rust and corrosion from the parts used in the Cyncra. Any painted or powder coated surfaces are on stainless steel or aluminium.
Bearing surfaces for steam valve and brew switch pivots are made of bronze with stainless steel interface, for extremely long life.
Operation and user interface
Hot Water: The hot water from the Cyncra utilizes a mix valve to control the delivery temperature. There are two solenoid valves, one for the steam tank and a second from the cold water. The cold water side has a needle valve so that cold water can be mixed into the hot preventing splatter for tea water, or allowing Americano water to be taken from the steam tank at a reasonable temperature.
Self-Bleeding Brew Groups: It is very important to remove all of the air from the brew tank water because air compresses and water does not. If air is left in the brew tank, several things can take place.
- In machines that have flow meters, the meter can be fooled into thinking that water has been used to brew coffee when it was actually used to compress air in the coffee tank.
- Heat transfer from the water to the group head can be impeded if an air gap is present between the group top and the water inside. This affects the machine’s brewing temperature stability.
- Scale build up is more likely to occur when air is present. The Cyncra will “self bleed” air from the brew groups when the brew valve is turned to the ON position because the inlet water tube is at the top of the group and the air is the first thing to leave the tank. Bleed the air from each brew tank in the Cyncra before brewing coffee. Because of the independent switches for turning on the electronics and heating elements, the air can be bled from the tanks before heating the water.
Service: Service for espresso machines usually revolves around two major issues:
- Hard water that causes scale build up
- Rubber parts that leak and wear out
The Cyncra is made to the highest quality standards. There is no carbon steel to rust and all rubber gaskets have been eliminated. The only gaskets used are for the heating elements and inlet/drain end plates and they are made of Teflon because of its ability to tolerate heat, it can be reused and conform to sealing surfaces.
Some rubber is unavoidable in espresso machines with the technology that we have today, o-rings and rubber seats in steam valves, rubber seats in check valves and solenoid valves, there is a rubber seat in the vacuum breaker and the pressure relief valve. Until better options are available, there will still be some wearing parts but these parts are easy to access and relativity inexpensive to replace.
Steam: The steam valves used are mounted to the frame for easy service. By removing the metal cover and the handle, adjustments can be made and rubber parts can be replaced quickly. The steam lever is a 90° of movement lever and has positive stops at both ends. It stays in place if you let go of it and is infinitely adjustable for steam flow. In a two-group steam tank, the dual heating element provides 2,000 watts on each loop for a total of 4,000 watts and in a three-group steam tank the dual heating element provides 2,500 watts on each loop for a total of 5,000 watts. Compared to La Marzocco, heating elements of 3,000 watts for a two-group and 4,000 watts in a three-group machine. The Synesso electronics run each loop of the heating element independently and this allows one of the elements to be set a few degrees cooler than the other, creating a situation where the steam tank in a three-group machine runs on 2,500 watts until heavy use is required then a second 2,500 watts turns on for a total of 5,000 watts.
The steam wands on the Cyncra are a custom designed dual walled wand that stays much cooler to the touch than convention steam wands. Our goal is help eliminate contact burns and the need for a burn clip plus it is much easier to clean since the milk has not scaled onto the wand. The base and the tip of the wand still get very hot and caution should be used.
Electronics: Solid-state DigiZone™ electronics control all the heating elements and each element is controlled by its own temperature probe. The temperature that the probe is reading can be viewed on the control panel by selecting the Zone that needs to be viewed; the temperature setting for that zone then can be viewed by pressing the Set button.
To change the temperature requirements for any one element go to the proper zone, press and hold the set button then push the Up or Down arrows to make an adjustment. This system is quite simple to use and allows each group to be adjusted to a different temperature if multiple roasts are being used. See Brew Temperatures and Coffee Roast for details.
The steam tank has two probes and an element with two separately controllable loops. This allows one loop to be set a few degrees cooler than the other cutting the power requirements in half until full power is needed. A second benefit to this system is that no one electronic component will be required to carry the full load of the 5000 watt steam tank element, rather two solid state relays carry the load each at 2500 watts.
If a failure should occur in the brew system, any one zone can be turned off by adjusting its temperature to zero, allowing the rest of the machine to continue functioning properly. If a steam tank zone fails, the remaining zone should work and run the tank at half capacity. It is my hope that this design will prevent the need to ever shut down a machine and wait for a service technician to make a repair.
Look and feel
The Cyncra is designed to look like the centrepiece of a high-end show style bar. The operator interface is detailed in a way that it is easy to use and shows off the skills of the barista. The brew actuators are large and polished, to show the importance and quality of work that is being done to provide the best possible espresso for the beverage being made.
The steam wands come straight out of the top of the fascia and then are formed to point over the drip tray; they can be rotated to the side of the machine to give the customers a clear view of the steaming process and then easily rotated back over the drip tray for cleanliness.
The back panel is designed to carry a large logo, this can be the customer logo or the Synesso logo, in either case it is also possible to top light this panel.
When designing the shape of the Cyncra, great efforts were made to keep the profile low and the curves smooth. The reason is both aesthetic and functional; the low profile allows the operator to interface with customers while making their orders and the smooth curves make a machine that is easy to keep clean.
Testing brew temperature
Tools Synesso Uses: Fluke 51 II Thermometer with K Type Bead Probe installed in a Portafilter with a double basket (14-16 grams).
Probe Location: : It is our belief that the only accurate way to measure the brewing temperature of an espresso machine is to have the bead of the bead probe just visible at the top of the packed coffee.
- If the probe protrudes above the coffee bed, it will not read the coffee bed temperature accurately.
- If the probe is buried close to the bottom of the coffee bed, it will give a low reading because the coffee is absorbing some of the water’s heat.
- If the probe is in the middle of the coffee bed, the curve that you see is the heating cycle of the coffee bed and not the temperature of the water that is being applied to the top of the coffee, which is the set temperature of the machine.
Portafilter Preparation: Pack the coffee and then brush away the surface to expose the probe. Do not use a sponge in place of packed coffee in the portafilter. A sponge will retain water and hold heat differently than coffee. To measure and claim an accurate temperature, you must brew shots of coffee with freshly roasted beans that have degassed for a minimum of two days and are no more than ten days old. If your beans are not fresh, ground properly or tamped to the proper pressure of 15 kg, the brew could be too fast and your reading will be high or it could brew too slow and the reading will be low.
For reference: Desired brew time between 20-25 seconds for a 60ml shot.
- The water temperature at the diffuser screw is about 1.1° C hotter than the water at the top of the coffee bed.
- The water temperature at the top of the coffee bed is about 1.1° C hotter than the bottom of the coffee bed.
- The temperature at the bottom of the coffee bed can be up to 1.6-2.2° C hotter than the water (espresso) delivered from the spout.
Conclusion
It is the goal of the Synesso Cyncra to set a new standard for espresso machines. Functionality, reliability, ease of service and handcrafted quality will place the Cyncra ahead of all others. Total satisfaction and extreme longevity will keep it ahead of the competition.
Mark Barnett — Head Designer and owner of Synesso™