Does the boiler have to be full on a plumbed in or flojet-ed machine

#1: Post by **jedovaty** » June 4th, 2012, 10:13 am

Hi:

I don't have a full-on espresso machine yet, and am curious about the operations of them, specifically the kinds one plumbs in. On those that have their own tank, like the typical home machines, I'm guessing you can fill it up however much or little you want to.

On a machine that is either plumbed in or attached to a 5 gal jug with a flo jet -- does the water have to be full in the machine / boiler? Or can it be kept at 1/2 or 1/4 ? Let's say the machine has a 4-6L boiler.

Hopefully I'm asking the question in a way that makes sense!

Thank you.

#2: Post by **allon** » June 4th, 2012, 10:26 am

These machines typically have an autofill circuit that keeps the boiler at the appropriate level by injecting water when the water level drops.

The water in the boiler serves several functions -
In an HX machine it heats the water passing through the HX.
In non-HX machines the boiler water supplies the group head with water.
The boiler water is a source of steam for frothing
The boiler water acts as a reservoir of heat energy to replace that heat which is drawn off during steaming or extraction. This reason is often overlooked.

The optimal level is dictated by the design of the machine and is typically automatically maintained.

#3: Post by **cannonfodder** » June 4th, 2012, 1:25 pm

jedovaty wrote:Or can it be kept at 1/2 or 1/4 ?

No. It needs to be kept full for the machine to function properly. You would have to modify it to run it at a lower water level. FYI, unless it is a double or single boiler (non heat exchanger) the boiler is not full anyway. You have about 1/3 of the boiler empty for steam. On a double boiler or single boiler, dual use, the brew boiler will be 100% full with a second steam boiler only partially filled, or you drain part of the water out of the single boiler before putting it into steam mode.