- Edited
I’ve thought about what might be happening by imagineering how I this could be created if one wanted to do so. and looking at the way the Elizabeths were made (factory photos of first production run…I can’t see how it can happen, or be made to happen, unless i’m missing something. The repositioning of the expansion valve is still within the sealed brew area, and they changed it for a much better and reachable/adjustable valve.
The V2 I had which I modified to a V3 still; has the old valve, as you can see from my review photos, and hydraulically is in essentially the same position (if not physically)
https://coffeeequipmentreviews.wordpress.com/2020/05/08/lelit-elizabeth/
So here is the image, just to orient people
- Expansion valve controlling brew pressure max
- Manometer take-off for pressure gauge
- Autofill solenoid for steam boiler, opens to fill steam boiler
- Exit port from ring group to vent solenoid
- Vent solenoid, opens at end of shot.
As you can see 1, 2 and 4 , all form part of the sealed brew circuit. The expansion valve is directly connected to the boiler, whatever pressure is experienced by the coffee, the same pressure is seen by 1, 2 and 4. The other numbered components take no part in this. The component under the autofill solenoid (3) is what does the steam preinfusion and incidently takes part in the clever way the machine does hot water. This component can’t have any impact as it still only feeds into the same sealed brew circuit controlled by the expansion valve.
This means any thermal expansion of water would be controlled ultimately by the expansion valve. My only possible conclusion is perhaps a shock wave caused by any slight airspace and water hammer due to closing of valves? Perhaps someone could try switching of bloom phase and steam preinfusion, just have a straight shot…then see if it happens