In our factory where the temperature spends a good six months of the year at or below 50F we have the boiler pressure of the Bosco set to 1.1 bar, as previously advised in an earlier post on this blog.
If you have your Bosco in more temperate conditions, for example, your kitchen or a cosy cafe then it is likely that you will want to reduce your boiler pressure further, down to 1.0 bar. Happily 1.0 bar is the same pressure as the Olympia Cremina that we have at home, although the indicated pressure on the Cremina gauge will often show a number more like 0.85 bar in my experience.
The group on most conventional espresso machines is designed to act a heat sink. however the group will run significantly cooler if the ambient temperature is significantly lower, or if the machine is operating in an area with significant air movement, or in the most extreme situation, outdoors.
until i conducted a series of experiments measuring the temperature of the water exiting the group with the machine placed beside an open window in winter i completely under estimated the extent to which the ambient temperature, and air movement, impacts on the temperature of the water exiting the group. it has a significant impact that you need to be mindful of if you frequently move your machine into different operating environments.
even a machine in a kitchen that is essentially ‘warm’ will cool sufficiently to be able to ‘taste the difference’ if you move it to sit right against a window with single glazing in winter, for example
If you are running your Bosco out side, indeed any espresso machine, in cooler temperatures especially, you are going to have to wind up the boiler pressure or the water temperature during extraction will be too low.