mini boiler size and material

[Espressoluver]

hi, i thought the mini VII steam boiler is 1.5 L, but when i tried to drain it, only 7-800 ml came out.
Is that by design so there is space for the steam? or is my pump/sensor not working properly?

Also, is the steam boiler stainless steel? what about the group boiler?

thanks for your help

[Endo]

hi, i thought the mini VII steam boiler is 1.5 L, but when i tried to drain it, only 7-800 ml came out.
Is that by design so there is space for the steam? or is my pump/sensor not working properly?

Yes. That's normal. It needs headspace for the steam. Also, the heater coils are in the bottom half of the steam boiler, which limits how much hot water can be extracted since the heater must always be covered with water to avoid oxidation damage. What this means is you only have about 300ml of hot water that can be safely extracted. Also, the mini's pump is not as fast as the rotary version, so it can't keep up with the water extraction. What all this means is that the designers needed to add a hot water limiter which prevents you from extracting more than 1 cup (250ml) at one time. Don't press the hotwater too soon after either, or you risk damage to your steam heater coil, which means you need to buy a WHOLE new boiler for $200 since the heater is a welded shut unit. So if you like more than 1 cup of hot water at a time for say a French press, (and you don't want to wait 2 minutes for refill and heating) you're better off with the regular Vivaldi. Personally, I don't mind waiting a minute or so for my second hot cup of water, since boiler water tastes horrible anyway. I use a good tea kettle for expensive teas or pour-over coffee anyway.

Also, is the steam boiler stainless steel? what about the group boiler?

Yes the steam boiler is stainless (the preferred material for steam boilers like LM, Synesso or Speedster). The group boiler is solid plated brass and very small at only 0.45L. This gives it a lot of thermal mass for added temperature stability, but is not so big that the water sits around long and alters the taste. It's the perfect design in my opinion! The only improvement I would make to the boilers to make it the perfect home machine is to make the steam boiler top removable (so it can be properly descaled) and attach the grouphead more solidly to the boiler, to avoid the "cold nose" problem and eliminate heating flushes. This is what the designers did after the Vivaldi when they changed companies and built the Dalle Corte Mini. Unfortunately, this machine has a bunch of other nagging issues which make it not the machine it was meant to be.