OK, so the Aurelias that are out there in coffee shops are basically the same as the WBC spec Aurelias, but not exactly. They can swap out the valves located in heat exchange intake and outlet, and valves in the group head, to achieve a near perfectly repeatable brewing temperature with only a 1 or 2 second flush time. My co-worker in Atlanta, David Lamont, did have in his possession a WBC spec Aurelia for a brief time, and he experimented with the Thermofilter device to find beautifully stable brew temperatures.
The WBC spec Aurelia with temperature stabalizing valves install
Nuova Simonelli has achieved stable brewing temperatures in a heat exchange machine by carefully controlling the flow of heat exchange water into the group head. Bear in mind that the group head holds 1 liter of brew water in a reservoir. While the NS people use their soft pre-infusion and ergonomic steam valve control as their big selling points, it is the ingenious temperature control that becomes the shining star on the crown.
Imagine if you will the water sitting in the heat exchanger for some long period of idle time. This water has become too hot to brew, while the 1 liter of brew water in the group head reservoir has become too cool. A careful injection of super heated water, coupled with appropriate convection to blend the two temperatures inside the group head itself, would yield brew water at a desirable temperature. Conversely, a heavy load of drink prparation would move the over heated water form the exchange to the reservoir, raising the heat at the group head. But again, activating the pump will blend the cooler HX water with the hotter reservoir water creating a flow of appropriate brew water into the portafilter. The 1 or 2 seconds of flush time will purge cooled water from the pre-infusion chamber and bring brew temperature water in place and ready for extraction. The NS people have said that longer flush times will raise the temperature of the brew water. This seems consistent with filling the reservoir with more and more HX water. This analysis is purely my synthesis of the information I have been able to gather from various sources and through communication I have had with those who have Scaced the WBC spec Aurelias. I may be wrong about the details of the temperature stabilizing process, but my explanation is an attempt to make sense of the facts that I do have, which are:
Fact 1- Aurelias for the WBC are not exactly the same as Aurelias currently being sold.
Fact 2- The difference in how the two set ups function lies in swapping out a few Gicleur valves located in the HX and the group head.
Fact 3- Aurelias without the WBC set up function like any other HX machine, only with a very slow temperature fluctuation.
Fact 4- Aurelias with the WBC spec valves hit the same brew temperature every time.
I do not know what the NS policy will be concerning retro fitting original Aurelias with a new set of valves, but if I owned one I would definitely asked about getting it done.
My experience using the Aurelia was very pleasant from a Barista’s perspective. There is good clearance between the bottom of the spouts and the drip tray which makes moving cups and shot glasses easy. The angle of the front ledge does give good sight lines to the working area. While some have found the steam a little fast, (reduced in the WBC spec, and cool pipes to the touch), I had no problem texturizing excellent milk. I was not bothered by the dribble of the pre-infusion chamber, but if you are NS has a part you can have installed that drains the excess drops in an unseen fashion.
All this leaves only one major complaint. Can NS style the appearance of the machine to be more appealing to the eye? They have other models that are a sight to behold, like the Adonis for instance.
Much more stylish, the Adonis offers curves and sparkles.