at the risk of sounding like a broken record, i continue to be impressed with LONDINIUM I’s ability to run the perfect group temperature whatever the ambient temperature
this mightn’t sound like a big deal if you don’t fully appreciate just how sensitive espresso machines are to the ambient temperature
if you need proof, try placing your espresso machine next to a window and open the window a bit and come back after 15 minutes and draw yourself an espresso – i’ll guarantee the brew temp will be way down
this typically means adjusting the pressurestat on the boiler to raise or lower the group temp, which isn’t always ideal as while it might bring up the idle temperature of the group it can result in the group over-heating when consecutive espresso are drawn
having tested LONDINIUM I for several weeks now in different environments we can say the the thermosiphon is capable of maintaining the correct group temperature in as little as 8C right up to 30C, and theoretically i see no reason why it won’t also be at the correct group temp in 40C and even 50C ambient
How can this be? Well, the trick is to make the thermosiphon with a oversized diameter pipe so at low temperature you can really move a lot of really hot water through the group. As long as you can achieve the correct group temp with a low ambient temperature, the magic of physics takes care of ensuring the correct group temp at higher ambient temperatures.
How? if the temperature of the water after it has been through the group is quite close to the temperature of the water inn the thermosiphon before it went through the group, the pressure difference between the two sides of the thermosiphon is less, causing the thermosiphon to flow at a slower rate. When the thermosiphon flows at a slower rate the group cools, causing the temp of the water in the thermosiphon after it has been through the group to be lower, which means the difference between the two sides of the thermosiphon is greater, and so the thermosiphon flows a little faster again. This process is continually in motion as the thermosiphon constantly seeks to maintain an equilibrium
As the ambient temperature rises it can be seen that the thermosiphon will flow more and more slowly. Given that the upper limit of the thermosiphon is zero flow, at which point the group temp adopt ambient temperature because unlike in a dipper it is not mounted on the boiler, we can confidently say that even if you live in a really hot part of the planet with ambient temperatures reaching into the 40Cs, the group on LONDINIUM I will still be at the correct temperature for a perfect espresso
Perhaps small things amuse small minds, but i find the perfection in the cup that results from such a simple device of physics to be fascinating and incredible; even more so after weeks of use and seeing how effective it is in its practical application