La Marzocco GS/3 vacuum breaker stuck closed? - Page 2

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Marshall
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#11: Post by Marshall »

JonR10 wrote:I'm at a loss. Perhaps you don't understand the function of the vacuum breaker....
More likely allon is expressing the common assumption that condensed steam is distilled water and should not contain anything but H20. Not everyone is an engineer or chemist. And not being engineers or chemists doesn't make people idiots.
Marshall
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JonR10
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#12: Post by JonR10 replying to Marshall »

Marshall - nobody called anyone an idiot nor inferred that (until you did).

The moisture collecting at the breaker is not just condensed steam but rather it is mainly boiler water that gets trapped above the seal due to the valve operation. My last post was intended to promote better understanding, not to belittle anyone.

This is why some machines (like my Faema) run some tubing from the breaker to the drain, to allow this water to drain away rather than collecting and evaporating at the breaker. It is my understanding that it is possible to do this as a modification on the GS/3 as well although I never tried it.
Jon Rosenthal
Houston, Texas

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Peppersass (original poster)
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#13: Post by Peppersass (original poster) »

allon wrote:Where do these deposits come from? Condensation should be pretty mineral-free.
I used the wrong word. JohnR10's description is correct, but let me see if I can make it a little more visual for you:

The valve is open when the machine is heating up. As the water begins to boil, a mixture of air and water is forced out through the open valve. The mixture spritzes around like crazy until sufficient pressure builds up in the boiler and closes the valve.

There's a short section of silicone tubing forming a sleeve over the top of the valve assembly. It's there to keep the spritzing water from getting all over the inside of the machine, and also to prevent insulation peeling off the inside of the top cover and falling into the valve assembly, sticking it open.

Unfortunately, the sleeve also allows most of the spritzing water to fall back on the open valve. Some of it goes back into the boiler, but the rest of it sits on top of the valve seat. Over time, the water droplets evaporate, leaving fine mineral deposits behind. The deposits build up and eventually prevent the valve from closing completely.

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Peppersass (original poster)
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#14: Post by Peppersass (original poster) »

HB wrote:False pressure occurs when the steam boiler is filled with a mixture of air and water vapor. When heated to a given temperature, air + water vapor exerts greater pressure than pure water vapor. This happens when a vacuum breaker sticks closed, i.e., the pressurestat is "fooled" into turning off the heating element at a lower temperature. Normally a vacuum breaker is open when the boiler heats, allowing air to escape so the steam boiler re-establishes an environment of pure water vapor.
Sounds to me like Dan is agreeing with my theory that the valve is stuck closed. Not sure if a PID gets fooled the same way a pressure stat does, but the false pressure symptom is what I'm seeing.

Anyway, I can end all this speculation by inspecting the valve, which I shall do next time I shutdown the machine.

nitpick
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#15: Post by nitpick »

Marshall wrote:More likely allon is expressing the common assumption that condensed steam is distilled water and should not contain anything but H20. Not everyone is an engineer or chemist. And not being engineers or chemists doesn't make people idiots.
Apparently that class includes the fine folks at Marzocco who engineered a $7K coffee maker that breaks if you turn it off.

:-)

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Peppersass (original poster)
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#16: Post by Peppersass (original poster) »

JonR10 wrote:This is why some machines (like my Faema) run some tubing from the breaker to the drain, to allow this water to drain away rather than collecting and evaporating at the breaker. It is my understanding that it is possible to do this as a modification on the GS/3 as well although I never tried it.
I purchased a replacement vacuum breaker from CC that has a hose barb on top. You can attach a silicone tube to the barb and route it to the drain box or outside the machine. But I haven't installed it yet. I need to measure the clearance to make sure there will be enough room between the top of the barb and the inside top cover to route the silicone tubing without putting a kink in it. Also, I'm a little skeptical that this valve will solve the problem. It looks to me like water will still be able to fall back on the valve seat, though it might be less than is currently allowed by the large plastic tubing sleeve, and it's possible that water trapped in the tube will keep air out and slow or eliminate evaporation.

The Speedster seems to have a different arrangement, but I'm a little confused by the photos I've seen. In this one and this one, what looks like a vacuum breaker is inserted into the top of the boiler horizontally. Seems like that would greatly reduce the amount of water falling back on the valve, but some water might still be left on it.

The text with this photo implies that the vacuum breaker is the item in the foreground with the plastic 90-degree hose barb fitting, and that what the other pictures are showing is actually the expansion valve. Seems to me it would be the other way around, with the vacuum breaker needing to be mounted directly to the top of the boiler. If the valve in the foreground is the vacuum breaker, it looks like the 90-degree fitting would allow some water to sit above the valve. But again, maybe insufficient air gets in the tubing to evaporate the water.

The stock GS/3 valve, and I think the valve I got from CC, rely on gravity to open the valve. So they have to be oriented vertically to work. But if the valve mounted on the boiler in the Speedter is a vacuum breaker, then it must use a spring to hold the valve open. That would allow positioning the valve horizontally or maybe upside down to allow water to drain away from the valve.

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erics
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#17: Post by erics »

. . . but I'm a little confused by the photos I've seen.
Those are boiler safety valves.
. . . with the plastic 90-degree hose barb fitting
That part is similar, if not identical, to the silicone 90 ell typically applied to the suction side of Ulka vibe pumps - a very common part that would eliminate your potential "kinking" problem and that of any other installation that utilizes that modified valve. The text associated with that photo you reference from JohnB is 100% correct.
Skål,

Eric S.
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E-mail: erics at rcn dot com

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allon
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#18: Post by allon »

Marshall wrote:More likely allon is expressing the common assumption that condensed steam is distilled water and should not contain anything but H20. Not everyone is an engineer or chemist. And not being engineers or chemists doesn't make people idiots.
That is exactly what I was expressing. I understand full well how vacuum breakers work.

You state it's an assumption...am I assuming incorrectly? I'd think that getting hot enough to boil the minerals would lead to bitter espresso ;)
Of course there are dissolved gasses, but these won't condense into a crust.

The water in the boiler starts to boil; this boiling water creates steam and pressure. Until the pressure is enough to lift the pin in the vacuum breaker, steam escapes. Because the machine was cold, some steam condenses on the cool(er) metal vacuum breaker and turns back to water - condensation. Some of the condensate is sprayed upwards by the force of more steam. This condensation contains none of the minerals that were in the boiler water. I think that is the water that you are seeing, but incorrectly assuming is mineral laden boiler water.

In order for boiler water (not condensate) to spray from the vacuum breaker, you'd have to have the boiler full of water.

So my assertion is that if the water on the vacuum breaker is not boiler water, but there is a crust forming, then the minerals must have come from elsewhere, such as dripping water from drying cups/saucers placed over the unit.

Water spritzing from the vacuum breaker can cause problems if there are electrical components nearby, but it isn't a source of minerals.

On CG, there is a thread that mentions that insulation from the interior of the cover can become detached and fall down into the vacuum breaker.
LMWDP #331

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Peppersass (original poster)
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#19: Post by Peppersass (original poster) »

allon wrote:So my assertion is that if the water on the vacuum breaker is not boiler water, but there is a crust forming, then the minerals must have come from elsewhere, such as dripping water from drying cups/saucers placed over the unit..
Mostly correct, but I doubt the debris is coming from the cups/saucers. The geometery is such that any debris from that source wouldn't fall in the vicinity of the vacuum breaker.

The steam probably starts to condense into water as soon as it exits the boiler, when it hits the brass fitting between the boiler and breaker valve. The water could be picking up metal oxide particles on its way through the fitting and out the valve.

Another possibility is that when the water sprays out of the valve and hits the insulation directly above, it's picking up tiny particles of foam or some other debris on the insulation, then dripping back down into the valve.
allon wrote:Water spritzing from the vacuum breaker can cause problems if there are electrical components nearby, but it isn't a source of minerals.
There aren't any electrical components in the immediate vicinity of the valve, but if the valve leakes due to mineral deposits holding it open, enough water spritzes out that it eventually drips down off the top cover and various pipes to the chassis. From there it can flow into the main electronics box. That can have very bad consequences. That's why a leaking vacuum breaker valve should be addressed ASAP.
allon wrote:On CG, there is a thread that mentions that insulation from the interior of the cover can become detached and fall down into the vacuum breaker.
Yes, that's the purpose of the silicone tubing sleeve I mentioned before. Without it, insulation can peel off the inside top cover and fall against the valve stem, holding the valve open. This happened to a number of early GS/3 owners. The silicone tubing was LM's fix. If the insulation peels off, the sleeve will hold it away from the valve stem.

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Peppersass (original poster)
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#20: Post by Peppersass (original poster) »

erics wrote:That part is similar, if not identical, to the silicone 90 ell typically applied to the suction side of Ulka vibe pumps - a very common part that would eliminate your potential "kinking" problem and that of any other installation that utilizes that modified valve.
Eric -- do you know where I could lay my hands on that part?