The coffee water 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 situated vertically, 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 degrees C. It is cooled down by flow-crossing the outgoing hot water with the incoming cold water.
At entering the coffee boiler the water first travels through an internal tube over the entire length of the boiler to accommodate quickly to the temperature present 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. This is a control loop feed-back mechanism. A nearly intelligent system, responding ahead, steering 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 degrees Celsius.
The controller offers an Eco mode, dropping temperature half way during longer periods of idle.
-shot timer, installed in full view, right next to group
-total consumed power (Watts) can be diminished by retracting an electric bridge at the centre solid state relay: whenever the heating element of the coffee boiler is activated, one of the steam boiler elements is now automatically de-activated. This brings down total wattage with 900 to 2.200Watt. (Standard max wattage is 3.100.) Yet hardly any effect can be noted in capacity. Heating up from cold will take a bit longer however. The bridge on the centre SSR is standard deleted on 115Volt machines.
-intuitive operation by lever. Group lever offers manual and automatic infusion
-one separate PID temperature controller for each boiler, displays in full easy view
-energy saving Eco mode on each temperature controller, for nights and/or weekends
-energy saving hot water system. Some cold is added to the hot water, so less heated water is needed. This mix provides a steady, non-spattering stream with the correct temperature to prepare Americanos.
-drip tray adjustable in height
-stainless steel filter holders with KvdW Bakelite handles
-Slow automatic infusion process, with step-less build-up of pressure to full extraction mode. This allows a finer grind, creating more surface, so a higher yield in the cup, less chance on channelling, preventing fines to travel down.
-wide choice in filter baskets, both sizes as types
-rubber group gaskets remain flexible forever, do not become hard or brittle
-membrane type group screen, very nice dispersion, less coffee sucked up by discharge of pressure at end of extraction. Remains clean longer.
-heat neutral polymer dispersion block, no loss of heat, no baking on of oils and fats, remains clean longer
-heavily protected heating element (extra safety level probe, cut-out switches)
-entire frame in stainless steel only, powder coated in crackle black
-large steam boiler capacity of 3.5ltr.
-large coffee boiler capacity, total of 2.1ltr.