OPTIONS:

The Speedster is equipped with two separately functioning boilers: one large steam boiler to produce hot water and steam, one boiler with group to heat water to brew coffee. Each boiler has its own electronic temperature controller system, heating element and safety devices, offering extremely precise temperature stability.

High capacity is secured by the large steam boiler, over-rated heating elements in both boilers, and a heat-exchanger inside the steam boiler, pre-heating the brew water for the large dedicated coffee boiler.

STEAM BOILER

The display is installed at the front of the machine. It is easy to adjust and offers an Eco mode for longer periods of idle, dropping temperature to 70 °C. The heating elements provide a powerful 1.800Watt. This is divided over two spirals of 900Watt each, mounted on one flange. There are no moving parts in the heating system. The steam valve has a large knob, stainless steel wand and a steam tip with 4 holes in fan-shape, each with a diameter of 1.2mm.

Activation of the hot water is done by a switch. The valve body on the machine  provides a connection between inner tube and outside wand, visually symmetric to the steam valve.

Two different hot water temperatures can be supplied by one toggle switch. Inside the machine hot water running from the steam/hot water boiler towards the hot water valve is directed first through a mix manifold. On this manifold 2 solenoid valves are installed, one for hot, one for cold water. The amount of cold water flow is regulated by an adjustable restrictor. Pushing the long lever toggle switch downwards activates both solenoid valves and the pump, resulting in a quiet flow of mixed water with a temperature below boiling point. When the lever of the toggle switch is pulled upwards, only the hot water solenoid is activated. This results in hot boiling water flowing directly from the boiler to the wand.

COFFEE BOILER

The coffee boiler is made in 3mm stainless steel tube and 6mm thick flanges. There is a large hole on top of the coffee water boiler over which the group is installed. The group is made in 4 and 5mm stainless steel. All stainless is 316L. The group head is welded to the group neck, the group neck in turn is welded to the boiler. All welding is done both on the outside as well as the inside to prevent possible crevices which would easily start corrosion. The neck of the boiler is oriented with a slight slope, to allow for a proper constant thermo-siphon heat flow inside, reaching the full length and height of the group. Both the cover as well as  the bottom of the group are removable, sealed by O-rings. Total capacity of boiler with group is 2.1ltr.

The cold water entering the machine is first directed through a heat-exchanger located inside the steam boiler. Exiting the heat-exchanger its temperature is higher than needed because the steam boiler runs at 135 °C. It is cooled down by cross-flow of incoming cold and outgoing hot water.

Entering the coffee boiler the water first travels through an internal tube over the entire length of the boiler to adjust quickly to the temperature inside the coffee water boiler.

The temperature of the coffee water is measured and controlled by a highly sensitive probe connected to a PID (proportional-integral-derivative) controller.  An intelligent system, responding ahead, managing the 900Watt heating element by pulses through a solid state relay. There is no moving part in the entire heating and controlling system. This set-up ensures an extremely fast reacting system as well as a very reliable one. The water temperature can easily be changed by just pushing a button at the front of the machine. It is adjustable to 0.1 °C.

The controller offers an Eco mode, dropping temperature to 50 °C during longer periods of idle.

GROUP

At first installation it is important all air is bled from the coffee boiler. Air can be compressed, water cannot. When the group lever activates the group solenoid valve and pump for the first time, all air is automatically expelled by the inrush of water because the pick-up tube sits right underneath the group`s cover. This is the highest point in the system where air would collect.

When the heating system reaches and maintains the perfect desired temperature, the challenge is to not suffer any variation in temperature until the water hits the coffee grounds. Water heated by the heating element will expand and flow upwards.  Law of nature then dictates that a thermo-syphon flow will commence. In the Speedster the warm flow continues to the very top of the group head. There it will cool slightly, sink and travel down the neck to the bottom of the boiler. The neck and group are specifically designed to offer ample space allowing the hot and cooler flows to pass each other. The “sweet spot”, the most stable temperature in this system, will develop at its highest point, right underneath the group cover. This is isolated by the thick stainless cover and the synthetic cover on top.

The pick-up tube is positioned right in that sweet spot, running to the 3-way group solenoid valve. This valve is installed at the lower end of the neck, right above the boiler, a position with temperature very close to that of the water inside the boiler. The valve itself is made of stainless steel. Stainless steel transfers heat 10-20 times worse than brass, and is of little influence on the temperature of the water flowing through.

When brewing, the water never leaves the coffee water boiler/group on its way towards the coffee. It runs via a tube inside the group, starting from directly under the group cover, to the stainless steel three-way solenoid valve. From the solenoid valve it is routed through another tube towards the bottom of the group. Both these tubes run parallel to the top inside the group neck. This path makes for an extra temperature stabilizing effect.

The stainless steel bottom plate of the group is at a low position, under the water. This causes its temperature to be below the temperature of the water. Water passing the bottom on its way to the coffee grounds, should not lose any of its heat to the metal bottom, therefore the synthetic dispersion block reaches up through the bottom plate. The water directly enters the dispersion block, it does not touch the metal of the group-bottom. The dispersion block is made of polymer plastic, a near temperature-neutral material to which the fats and oils in the coffee do not easily adhere, effectively keeping it clean for a long time. It consists of two pieces and makes for an even distribution of brew water over the group screen, and is fixated by 2 screws.

The group screen is held in place by the surrounding group gasket. To remove the gasket with screen for controlling, cleaning or replacing, a special tool is provided with each machine in the Barista Kit. The gasket sits against the bottom of the group which has a small outward pointing ridge. This ridge is pushed into the gasket each time the filter holder is locked into the group, as an extra sealing surface. The slight moving up of the gasket ring, because of the flexibility of the material, provides an ergonomically correct soft comfortable feel for the barista. Full sealing is achieved without having to pull the filter holder firmly.

The group gasket is made of heat resistant rubber material that does not harden and go brittle. It remains flexible. The group screen reaches up and sits against the bottom of the group making it very strong. Together with the rubber gasket surrounding the screen, it is impossible for coffee grounds to flow back towards the group-valve. The supporting horizontal base of the screen is thick to resist deformation. This base is perforated and covered with a stainless steel membrane, not a woven mesh. The membrane provides homogeneous dispersion of the water during extraction. It also strongly filters the water sucked up when pressure is discharged at the end of the shot. This again ensures a cleaner inside of the group-valve.

INFUSION

In general, the importance of pre-infusion seems to remain under-estimated. Variation in brewing temperature tends to result in a broad spectrum of different flavours extracted from the coffee grounds. On machines offering a strictly defined brew temperature, a well-executed pre-infusion becomes imperative, otherwise they might not be able to extract the full range of complexities hidden in the coffee.

Properly infusing the grounds makes for an even wetting and swelling of the grounds. This careful wetting and slow swelling reduces the chance of channelling inside the coffee-bed. This process also locks in the fines, preventing them from travelling downwards and clogging the filter. In addition, pre-infusion allows the fats and oils in the coffee grounds to warm and soften, ahead of the actual extraction with high pressure. This clearly results in a higher yield of solids in the cup. These fats and oils are the carriers of the delicate aromas and flavours.

A good infusion system allows for a finer grind. All the smaller coffee particles together offer a larger surface making it easier to wash out the oils and fats. The brewing lever has three positions. Fully up is off. Halfway offers a manual infusion at water mains pressure, the group solenoid is open, pump is not activated. All the way down will start the pump. When the brew process is started by moving the lever all the way down, the group solenoid valve opens and the pump starts to run.

A 0.6mm (flat-) jet is positioned at the entrance of the group-valve, in between group-valve and group-neck, thus restricting the maximum flow-rate. As soon as the solenoid opens, water at water mains pressure or pump-pressure runs to the coffee-bed. Water reaches the coffee grounds and sinks into the coffee bed. All pressure inside the coffee boiler vanishes, because lots of empty spaces had to be filled: tube, dispersion block and coffee bed. The result is a soft and full saturation of the coffee grounds, with hardly any pressure at all.

After the 0.6mm jet has allowed enough water to completely soak the coffee-grounds, the rising pressure is first absorbed by the spring loaded pre-infusion cylinder. This is a progressive process as the springs generate more force the more they are compressed. The piston`s shaft moves out through the front panel as a visual indication of this infusion process. As soon as the piston reaches maximum travel, pressure will rise to the full 9 bar extraction pressure. This build-up of pressure is steady and gradual, ensuring the integrity of the puck remains unaltered.

An additional aspect of the progressive pre-infusion cylinder is flushing of the group-valve with clean water. After the extraction process is ended, remaining pressure inside the basket is purged through the internal tube and valve to the drain. When this pressure has dropped the springs push the piston back and water inside the cylinder is forced through the valve towards the drain. This rinses the internals of the solenoid valve. Note that the tube between group-valve and coffee is not flushed, so back-flushing is still needed once in a while.

The pressure gauge is connected to the pre-infusion cylinder. This means that as long as the solenoid valve is closed there is an open connection to the group sieve and the gauge will display 0 pressure. With group-valve active, the gauge displays the actual pressure on the coffee-bed, not the pump pressure. The barista can monitor exactly how infusion and extraction develop.

The mid-way position of the lever offers the possibility to play with infusion pressure and duration at will.

As soon as the lever is moved, the steam boiler fill-up system is de-activated to prevent any loss in brew-pressure that could possibly damage the extraction process.

SAFETY

The steam boiler has two probes to monitor the level of the water inside. The lower probe is installed just above the heating element. When the machine is fired up and filled for the first time, the level controller interrupts power  to the temperature controllers, and thus the heating elements, until the lower probe touches water. At first installation, the coffee boiler starts to fill as soon as water mains is connected to the machine. Steam boiler fill-up requires that the electric mains is connected and the main switch is turned ON. The installation procedure safeguards that the coffee boiler is at least partly filled before the lower level in the steam boiler is reached. Both elements inside the boilers are thus submerged before the lower probe in the steam boiler detects water. This ensures the heating elements cannot be turned on while not being cooled by surrounding water. When, during normal use, water in the steam boiler would fall below safety level (e.g. by very prolonged dispense of hot water) the temperature controllers will shut down completely with displays going dark.

Fill solenoid and pump are activated as soon as the higher probe does not detect water (provided that the group-valve is not active). Shortly after water touches the operational level probe again, the level controller de-activates the fill solenoid and pump.

Both electronic temperature controllers have a restricted upper temperature programmed. When this temperature is reached no more signal to the solid state relay is sent.

Each boiler is equipped with an overheat cut-out switch. When this switch detects too high a temperature, it will disconnect power to the element. The steam boiler is equipped with a safety valve. The coffee boiler system, including the heat-exchanger, is equipped with an expansion valve. The group solenoid valve may act as a second expansion valve, rated at 15 bar, in the event the original expansion valve would fail to relief pressure.