For Silvia owners confused about temperatures surfing, these are results Ive obtained on my machine which has a 100C thermostat.
Room temperature: 22C. Machine pre-heated for 30 minutes before times and temperatures taken.
Temperatures taken with a K-type thermocouple attached to the top of the boiler, readings with a digital multimeter.
The heating light is forced on by bleeding water through the group, with portafilter attached, but basket empty, until the light comes on.
Heating element light comes on at 0 seconds, temperature 92-94C degrees
Heating element light turns off at 50-52 seconds, temperature 102C degrees
***PULL SHOT AT 62-65 seconds, temperature 108C degrees. (108 at boiler roof = water at 95C
exiting shower screen)
At 30 seconds, the top of boiler temperature is 88-90C degrees --far too cold.
at 40 seconds the top of boiler temperature is around 95C --still far too cold. Remember, the water exiting the shower screen is around 13C colder than the top of boiler. It is qute likely that those suggesting pulling shots at 40 seconds confused the boiler temperature of 95 degreees, with the supposed water temperature. They may also have used the older machine with a 110C thermostat.
The maximum temperature reached is 115C degrees, at around 80 seconds. Thermal dynamics mean the water, and boiler, keep heating for 30 seconds after power is no longer delivered to the heating element.
The temperature stays within +- 1 degreee of 115C for another whopping minute before it begins the descent.
Therefore the Silvia is at its most thermally stable from 120" to 2 20" after the light comes on --- but the downside is that the temperature then is 115C --probably a tad on the high side for a shot, but Im going to give it a try to see what it would taste like.
The most obvious variables which would influence temperature surfing are:
--ambiant air temperature
--how cold the water poured into the tank is
--length of pre-heat time
--accuracy of test equiment!
--accuracy of the thermostat
Hope this all helps brew a better coffee from a pretty good machine.
Robusto
Room temperature: 22C. Machine pre-heated for 30 minutes before times and temperatures taken.
Temperatures taken with a K-type thermocouple attached to the top of the boiler, readings with a digital multimeter.
The heating light is forced on by bleeding water through the group, with portafilter attached, but basket empty, until the light comes on.
Heating element light comes on at 0 seconds, temperature 92-94C degrees
Heating element light turns off at 50-52 seconds, temperature 102C degrees
***PULL SHOT AT 62-65 seconds, temperature 108C degrees. (108 at boiler roof = water at 95C
exiting shower screen)
At 30 seconds, the top of boiler temperature is 88-90C degrees --far too cold.
at 40 seconds the top of boiler temperature is around 95C --still far too cold. Remember, the water exiting the shower screen is around 13C colder than the top of boiler. It is qute likely that those suggesting pulling shots at 40 seconds confused the boiler temperature of 95 degreees, with the supposed water temperature. They may also have used the older machine with a 110C thermostat.
The maximum temperature reached is 115C degrees, at around 80 seconds. Thermal dynamics mean the water, and boiler, keep heating for 30 seconds after power is no longer delivered to the heating element.
The temperature stays within +- 1 degreee of 115C for another whopping minute before it begins the descent.
Therefore the Silvia is at its most thermally stable from 120" to 2 20" after the light comes on --- but the downside is that the temperature then is 115C --probably a tad on the high side for a shot, but Im going to give it a try to see what it would taste like.
The most obvious variables which would influence temperature surfing are:
--ambiant air temperature
--how cold the water poured into the tank is
--length of pre-heat time
--accuracy of test equiment!
--accuracy of the thermostat
Hope this all helps brew a better coffee from a pretty good machine.
Robusto

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