I do realize that this is getting a little OT but here is a "real-life" pic of the changes in water level for a Quickmill boiler as she cools down from ~252 F to ~72 F.

As a side note, the weight of the steam in the boiler at ~252 F is ~0.00076 lbs and, upon condensing, has negligible effect on water levels. The reduction in water height (uncovering of the probe) is the cause of the autofill on startup.

If I had an espresso machine w/o a vacuum breaker valve, I would crack open the steam valve when shutting down to avoid the creation of a vacuum as the machine cools. I would not think the vacuum could cause any damage to the boiler itself but there are other components that may not fare as well over time - a pstat membrane and/or contact set as an example.

Yes. This explains the auto-refill I often get at startup.

While we are looking at your diagram (sorry, slightly OT again but I've been meaning to ask):

What do you think are the upper and lower limits or "working range" of water in the Anita boiler?

Endo wrote:What do you think are the upper and lower limits or "working range" of water in the Anita boiler?

The short answer is - I don't know. The autofill circuitry certainly is the bulk of the complexity on the Quickmill Gicar box but EXACTLY how it works is beyond me-at least for now. FYI, prior to writing this, I measured the cold water level in Anita to be 4.50 inches from the bottom.

Just curious if the heater coils are ever exposed to air.

On my Mini Vivaldi they limit the hot water shots to 6 oz at a time for this reason (using some sort of control logic mod on the board, I assume). On a permanently mounted heater/boiler unit, I assume this would be more critical than on the Anita's replaceable heater.

pdx wrote:If your steam boiler cooled down (element fails to heat, somehow turns off, whatever) & the steam & water cool & contract the pressure can drop below atmospheric pressure (if you don't have a vac breaker valve.) If you plunge a wand into milk & open the valve you suck it right into the boiler.

I did that once (through sheer stupidity) on a 'steam toy'... the little thing drank an entire pitcher of milk! I just stood there watching the milk disappear

Regards, Henry

That sucks.

First time firing up my Elektra, the vacuum valve was stuck shut just a little, and it falsely pressurized the tank. When I hit the hot water tap, water flowed cold, and I figured that was how it ought to be since the water line was pressurized.

Then it heated up just a little, I hit the steam wand once, and the valve went POP and suddenly all the pressure went flat and the water flowed no more.

I thought for sure something had snapped and I was completely heartbroken.

Then I read this fancy article and realized I just needed to let my boiler come up to temperature.

It's all happy now.

An offline note from a commercial espresso equipment repair technician on the practical side of this question:

repair technician wrote:The answer is simple - if a manufacturer does not have a vacuum breaker or an over pressure valve on their machine it will NEVER get ETL, UL, or NSF approval.

NSF says the machine can suck milk up into the boiler and it happens all the time in commercial restaurants. Waiters and waitresses leave the pitcher of milk on the driptray with the steam arm in the pitcher. I have had to take apart no less than 10 commercial machines to clean the boilers of milk.

Then, perhaps it is time for an R-rated pic of that Maximatic fill cap to see if it functionally resembles this : http://auto.howstuffworks.com/cooling-system7.htm

HB wrote:An offline note from a commercial espresso equipment repair technician on the practical side of this question:

Ahhh. That makes sense now.

I wonder how much extra cost is added to the prosumer machine just so it can get ETL approval? I'm starting to understand why a G3/3 costs $7500.

Or another way to look at it...

How much of the prosumer pricetag goes towards actual better taste and how much towards certifications which are useless to the home barista?