Single boiler, full of water, how does it steam?

[hbuchtel]

Ok, there is probably a simple answer to this, but I haven't been able to figure it out so I hope y'all can help-

As I understand it, on single boiler machines (like the Silvia) the boiler is filled with water. If this is the case, how can it steam without a bunch of water sputtering out the steam wand?

Is there always a pocket of air at the top of the boiler?

Thanks!

Henry

[HB]

You have to blow water out of the steam wand until there is enough "headspace" to froth milk. These types of espresso machines usually have less headspace than a steam boiler whose water level is controlled by a sensor, so the steam is wetter. The boiler is refilled with water to return to brew mode by turning on the pump until a solid water stream exits the steam wand. If there's an air pocket in the boiler, it's not intentional.

[JimG]

Don't forget, steam is water. Inside the boiler, the pressure is high enough to keep the water in liquid state even though it is much hotter than "boiling point." As the water leaves the boiler, the pressure drops to normal atmospheric pressure, and it flashes to steam.

Jim

[hbuchtel]

You have to blow water out of the steam wand until there is enough "headspace" to froth milk. These types of espresso machines usually have less headspace than a steam boiler whose water level is controlled by a sensor, so the steam is wetter. The boiler is refilled with water to return to brew mode by turning on the pump until a solid water stream exits the steam wand. If there's an air pocket in the boiler, it's not intentional.

Great, that makes sense.

Umm... could you potentially slow the ramp up in pressure (during brewing) by leaving more headspace in the boiler? Would this cause some other problems?

Don't forget, steam is water. Inside the boiler, the pressure is high enough to keep the water in liquid state even though it is much hotter than "boiling point." As the water leaves the boiler, the pressure drops to normal atmospheric pressure, and it flashes to steam.

So you don't actually need any headspace?

If the big bubbles that you get while boiling water in an open container are the water vaporizing, then in a pressurized boiler there would be no bubbling. But how about when you open the steam valve?

Thanks a lot for the replies!

Henry

[HB]

Umm... could you potentially slow the ramp up in pressure (during brewing) by leaving more headspace in the boiler? Would this cause some other problems?

A needle valve (gicleur) is a better way to accomplish that end. A partially full boiler (or partially empty, depending on your world view) won't help the responsiveness of a surface-mounted brew thermostat either.

[2xlp]

If the big bubbles that you get while boiling water in an open container are the water vaporizing, then in a pressurized boiler there would be no bubbling. But how about when you open the steam valve?

well thats part of the flash boil. note that you'll also have a bit of water come out for the first few seconds of steaming too.

[erics]

Silvia's boiler water level is maintained by a standpipe which rises to within a tad over 3/4" of the top of the boiler.



This standpipe also serves to keep the heating element covered under normal conditions and any water above the standpipe is exhausted when the 3-way opens.

Eric S.

[hbuchtel]

Silvia's boiler water level is maintained by a standpipe which rises to within a tad over 3/4" of the top of the boiler.
This standpipe also serves to keep the heating element covered under normal conditions and any water above the standpipe is exhausted when the 3-way opens.

Eric S.

Thanks a lot for posting that diagram!

It appears that the standpipe design is common to other single-boilers like the Gaggias and smaller Saecos etc. Even the ones without 3-way valves have it, which is a bit confusing, but it should keep the element safe at any rate.

Any idea how the cheaper Gaggia models maintain the headspace? The Gaggia Espresso for example? (w/out 3-way valve)

Henry

[erics]

Good Morning Henry -

The Gaggia Espresso appears to have a standpipe also.

http://www.partsguru.com/GaggiaEspresso.html

Eric S.

[hbuchtel]

The Gaggia Espresso appears to have a standpipe also.

http://www.partsguru.com/GaggiaEspresso.html

Eric S.

Ah, more diagrams, life is good!

It seems that 'have standpipe, no have 3-way valve' machines would need to bleed off a bit of water (as Dan mentioned above) before steaming.

I'll be getting one soonish, so I should have some first-hand experience soon.

Henry (13 hours off )