Hello,
If anyone could explain (or point me in the direction of an existing explanation) how the water level is regulated in the boiler of a non HX lever machine I would appreciate it. I imagine there is a tap, either manual or auto, to fill the boiler, but what kinds of taps or valves are used? How does the valve work if the boiler pressure increases beyond the pressure of the water on the upstream side? As shots are pulled, the water volume in the boiler decreases, so what happens to compensate for this? Can a completely manual water input valve be used? I am building a machine from scratch, so hence the daft questions.
Thanks,
Tim

How does the valve work if the boiler pressure increases beyond the pressure of the water on the upstream side? As shots are pulled, the water volume in the boiler decreases, so what happens to compensate for this? Can a completely manual water input valve be used?

-Doesn't happen unless you've got very low line pressure
-steam volume increases
-yes

Thanks Bluecold,
Does a 6 litre boiler allow steam production and espresso production at the same temp/pressure?

You are describing a machine with a simple dipper tube from the boiler that fills the group cylinder. Generally the boiler is filled from a line at some pressure higher than the boiler and usually when the boiler is cold....even if at 1 bar or other similar operating pressure the line pressure will be higher unless you regulate the line with a valve. The addition of cold water to the boiler really drops the temp and pressure rapidly so this is not an event that one does with any great frequency while pulling shots at temp and pressure. Your heat controls on the dipper group are generally barista skills...getting the cup temp right, warming the group, cooling the portafilter etc. You pull shots and steam at the same boiler pressure setting as it is not practical to be switching back and forth unless you have some extreme dual control system, which is not really needed, just the barista skills to get the shots to turn out like you want them....even engineering the espresso blend for temp as well. The hx system does allow continuous steam at a higher pstat setting but is no substitute for the obervational skills and barista technique needed for any good espresso production from either the most complex or the most simple machines.

Doesn't a large addition of cold water to a heated boiler/element risk damage to the element itself?

-Cecil

I am just observing from personal experience and extrapolating to a real world commercial machine situation. You have a 5L boiler and a single group machine....too small for a busy coffee bar in the first place, but let's say you have a club machine anyway and you get busy....you are going to pull shots and steam from the 5L until you hit a slow patch and then will refill the boiler a little at a time as not to overcool the setup and have to wait 15 or 20 minutes for the heat to all get back up. Depending on the business (after all we are talking about commercial machines) the number of groups and the size of the boiler goes up.....I don't think in the real world the barista gave much consideration to expansion of elements and such.
The HX was a good solution to this problem, even with the single groups since the boiler only was used for steam and the water faucet, thus minimizing the need to refill the boiler as much while keeping up a steady rate of espresso brewing.
There are a lot of factors worth considering on the small boiler home machines that from observation were not worried over much in the commercial units.

Yes you are right the larger boiler would reduce thermal shock if it was filled in a optimum way. I was worried more in a worse case way.

I thought we were talking about manual filling where things could get to a bad place if you were not being attentive.

-C

I own a Conti Prestina which is a fairly robust single group machine that lacks some of the prettiness of Faemas etc. It is a "flush to warm the group machine" with ~ 20+ pounds of brass group and lever stuff hanging out in the breeze. That means that it is most happy with back to back shots and then the group is very stable.

It is a manual fill machine and has a 5 liter boiler and only ~1Kw of power. At home I have it set to 1.0 bar for the few shots in a day that I may pull.
If I take it to an event, I amp up the pressurestat to about 1.2 or 1.3. That keeps the boiler heat on a bit longer and allows me to add boiler water from the Flojet® between shots. I can pull about 2 shots or more in three minutes at that setting. The 5gal. bottle is at room temp so there is not a great amount of heat needed to keep the machine operating.
Cheers
-Richard

So with the pressure from the flojet do you just hit a button to do a manual fill or is it still automatic?

-C

Hello,
There is a little lever at the left front of the machine. You can see the slot where it is under the rubber band. The lever goes into the steel plate attached to the brass valve with the whit tube coming out to the left. These are arrival unpack photos taken at UPS for insurance purposes before I started repairs and setting it up. It traveled 1400 miles on its head and I started shooting photos at UPS where it was delivered. UPS packaging fault ruined most of the sheet metal.

-Richard