How temperature stable is the new Breville Dual Boiler? Would you believe more temperature stable than even a La Marzocco GS/3? I'm not kidding. I had to type out these numbers for an email I sent, so I'll repeat them here. From my Sunday testing session o the Breville Dual Boiler:
Pull 25 second shot; pause 30 seconds between shots, measure temperature at 15 second point for each shot. Remove the scace'd portafilter between each shots. Do test for five shot pulls. Programmed machine temperature is 201F. Remove portafilter (with scace) from the grouphead between shots.
Measured Temperatures: 1) 201.7F; 2) 201.4F; 3) 201.4F; 4) 201.1F; 5) 201.4F.
Average Shot Temperature Test
Measuring the temperature average across a 25 second shot, starting measurement at 10 seconds in.
Test parameters: insert Scace'd portafilter, starting temperature above 175F for each measurement test (the PF comes up to temperature quick in a fully hot groupehad). 25 second shot pull. Programmed machine temperature is 201F. Commence Fluke temperature measuring at 10 seconds in, hold (on fluke) at 25 seconds. Pause of about 2 minutes between measurements. Record average, minimum and maximum temperatures for each shot pull between 10-25 seconds.
Test 1: Avg: 200.5F; Min: 199.6F, Max: 201.2F
Test 2: Avg: 201.2F; Min: 199.8F, Max: 201.8F
Test 3: Avg: 200.7F; Min: 199.7F, Max: 201.4F
Test 4: Avg: 200.6F; Min: 199.5F, Max: 201.0F* (held 201 for at least 7 seconds)
Test 5: Avg: 201.1F; Min: 200.0F, Max: 201.5F
Bottom line - this Breville Dual Boiler is really stable - actually a bit more stable than the GS/3 tests I ran some time ago. I blame this success on the Breville's PID controlled grouphead thermostat.