Vibiemme Domobar Super - sudden pressure drops / pump noise change during shots - Page 4

[HB]

CafeIKE: your instructions refer to installing a Manual Overfill Switch to prevent the boiler from filling during the descale process. I do not know whether that is something I can do. Your instructions suggest that switch simplifies the process - is there a more complex version that doesn't involve messing around with the innards of the machine?

Simply draw enough water from the water tap until the boiler refill kicks in. That will refill to the tippy-top and prevent an inopportune boiler refill while descaling the HX.

For the record, even if you did accidentally draw (citric acid) descaler into the steam boiler, it's no big deal. You would simply flush down the boiler a couple times as if you were descaling the steam boiler. Remember citric acid is consumable, so it's only a matter of rinsing out its sour taste.

[Bex]

Okay...

Well, here are the plans, then:

1. Stop by hardware store today to pick up tools to pull the mushroom and check it.
2. Also, order descaler. Any reason to use citric acid and not something like CleanCaf?
3. Order lubrafilm for the OPV screw.
4. Check mushroom.
5. Descale.
6. If it's still messed up.....?

[HB]

Any reason to use citric acid and not something like CleanCaf?

CleanCaf has detergents. Don't use it in a steam boiler unless you want your espresso machine to blow soap bubbles for a month.

[Bex]

ha! Gotcha. Will order citric acid instead.

[mhoy]

The easiest place to get Citric Acid is a home brew store. They use it to clean their equipment and it's like $4 a pound (or so).

Mark

[erics]

For this PARTICULAR descale, I would say that the most CONVENIENT approach would be to simply visit your local Safeway or other food store and buy a bottle of "Sour Salt" - about $2 and saves a lot on shipping and handling the citric acid. Sour salt and citric acid are identical.

Getting to the gicleur on the Vibiemme simplies requires a 7/8" wrench - it may be a tight fit so a simple adjustable wrench (crescent wrench) could be a better choice. Removing the mushroom requires a 5 mm allen head wrench and is best done with the brew valve in the off position. Holding the mushroom up to light while looking at the bottom, the four holes which feed the gicleur chamber should be clear. Looking at the center of the mushroom should reveal a clear gicleur. This procedure is similar to holding a piece of paper with several pin holes up to light - very easy to spot the pin holes and their condition.

If this doesn't solve your problem, it would seem that a trip to 1st-line is in order and you are welcome to stop in Silver Spring, MD on your way (I assume you are someplace in Virginia) for a little more diagnosis. More info on the digital thermometer you purchased and my address and phone number are on my crude FTP site: http://users.rcn.com/erics/

[Bex]

Thanks, eric. Here's hoping. I repeat my "mechanical things are weird" statement from earlier in the thread. Amazing what can happen just removing and re-inserting the OPV screw.

[HB]

Amazing what can happen just removing and re-inserting the OPV screw.

That said, espresso machines are not rocket science either.

If the brew group has no obstruction and the gauge holds steady during an extraction, the falloff in espresso quality you report is not related to brew pressure, despite the fact that you recently twiddled it. I've been fooled once or twice by assuming an adjustment I made was the cause of a subsequent problem. For example, once the roaster happen to change their blend for a new crop, requiring a different brew temperature while I was doing temperature profiling of a new espresso machine. For days I assumed the dramatic taste change was because of the different flush routine. Oops.

[Bex]

Though for the sake of completeness: same coffee in the grinder before/during/after this tweak, and it's less than 2 weeks old. Espresso Aficionado from CCC and I'd gotten pretty good at it with this bag.

[cafeIKE]

CafeIKE: your instructions refer to installing a Manual Overfill Switch to prevent the boiler from filling during the descale process. I do not know whether that is something I can do. Your instructions suggest that switch simplifies the process - is there a more complex version that doesn't involve messing around with the innards of the machine?

The idea of the OverFill is two fold :
1 - if only descaling the HX, stops the boiler from ingesting any descaler.
2 - when descaling boiler, raises the level above the water line, so the descaler can remove any 'ring'

There are two ways to do it other than adding a switch:
- Remove the boiler fill sensor wire and let the pump run for a full minute. Reconnect the wire.

OR
- AFTER the machine is hot, raise the left side, looking from the front, by placing a couple of espresso cups under the feet. This should cause the water level to lower under the sensor and over fill the boiler slightly. Remove the cups while descaling the HX.

IMO, there's no point descaling the inside of the HX and letting the outside continue to scale up. Do a full descale.

[Bex]

Pulled the mushroom tonight and there was a ring of green gritty stuff around the bottom of the mushroom, and a bit more of it near the top.

I was not able to stop and get any citric acid, so I cleaned what I could. eric, I couldn't see little holes in the outside of the mushroom, but I think it's because I must not be looking in the right place.

I replaced the mushroom and powered the machine on, hoping for different behavior. No dice - nearly the same behavior as before. I say nearly, because there is this change: before the pressure ramp to 8 bar was immediate (flip lever, needle goes to 8 immediately, blind filter or no filter). Now, it still gets to 8 bar, but it's not immediately. It takes about a second or so - noticeable difference. Ramp up to brew pressure then occurs, which was hitting 10 bar instead of 9.5. So same behavior, with little differences.

[erics]

In this post: vibiemme-domobar-super-slow-flow-rate-t6196.html there are flow numbers, pressures, and a drawing of a grouphead showing you the location of the "4 holes."

While it is a little difficult to imagine that a partially clogged gicleur screen can do what it did in the referenced post, the results speak for themselves (and I'm sure the owner was happy).

[Bex]

Did some testing this morning. Right now it's pumping out 2 oz in 13 seconds, so definitely far off from the expected volume. Pressure response is the same as noted in the last post.

Wiping the scale from the mushroom (apparently) caused a change in performance. If you watched the video, you saw how long it took to flush down to 200 degrees, and how the temperature did not drastically drop during the shot. Last week - well before removing the OPV screw and the current "8 bar" situation - I lowered the pstat to 1.1 after discussions with eric. That led to the grouphead idling around 207 instead of 213, but the flushes still took a very long time and there were no drastic drops during the shot - in other words, if I started the shot at 200, it would spike to 204-5, then fall to 198 over the shot.

Today, the flush was very rapid - twice as fast as I am used to. The grouphead was idling at 207. When I started the flush, temp jumped up to 211ish, which is normal for me, but immediately began to fall, and I'd say that after 5 ounces it had fallen to 200 (incidentally, I think this lines up with what I expected from VBM). So I pulled the shot at 200 as I have been doing, and the temperature plummeted to 194 by the end of the shot. The next shot I only flushed to 204 and the shot ended at 198.

I did not try straight espresso but the cappas were better.

It will be interesting to see what happens after the descale. None of the grocery stores in my area had sour salt / citric acid in stock, so I've ordered some from CafeIKE's link.

[mhoy]

Nice to hear your flush has gotten back close(r) to normal.

...
None of the grocery stores in my area had sour salt / citric acid in stock, so I've ordered some from CafeIKE's link.

I know what you mean, I tried a couple of different Safeways, Whole Foods, two drug stores and then finally settled on driving to the Brew Supply store.

Mark

[quar]

Just another data point - this same "problem" occurred with Anita this morning and I LOVED IT. About 1/3 of the way through the shot, brew pressure instantly dropped from ~8.5 to 7.0, the vibe pump sounded dead quite.

Yes! That's the same thing that my Anita has started doing intermittently. I was afraid to let the shot keep going, but loved the sound.

Any further insight on what is causing this?

Mike

[erics]

The only culprit that comes to mind (at the moment) is an intermittently leaking boiler fill valve. See here:
http://users.rcn.com/erics/Hx06_vib.jpg

Certainly the inlet to the boiler fill valve is subjected to pump discharge pressure whenever a brew cycle is initiated.

[Bex]

Wow.

I bought some white vinegar and soaked the mushroom & gicleur screen per instructions eric sent me.

Reassembled, and the pressure gauge now shows normal performance: initial pressure starts at 4ish and ramps up to the set pressure (almost 10 in this case).

Additionally, the flow is hitting the standard parameter that eric provided - 2 oz in 8 seconds.

I will try espresso in the morning but am very encouraged.

I am not qualified to say whether the "pressure drop/noise drop" seen at the start of the thread - which has disappeared during the pendency of the "immediate 8 bar pressure" issue - was also caused by scale, but I am tending at this point to write the whole thing off to a buildup of scale.

I will report more in the coming days. I have some citric acid arriving soon and will do a full descale. If the "pressure drop" issue does not reassert itself, it looks like we've found our culprit.

Thanks to everyone who has helped in this thread, especially CafeIKE and erics.

[Bex]

Observations from this morning:

We aren't done yet. Came down this morning and the machine was at 173 degrees. Had to flush some water to "wake it up" and make it come up to temperature. I am just going to assume internal scale is causing this issue, just like the rest.

3 shots pulled, plus two blind backflushes, no pressure issues.

Had to make major grind adjustments (5 to 4.5 on my CMH) to pull a good shot. But that shot was great.

[Randy G.]

We aren't done yet. Came down this morning and the machine was at 173 degrees. Had to flush some water to "wake it up" and make it come up to temperature. I am just going to assume internal scale is causing this issue, just like the rest.

I have experienced that about three times. If the machine is left on, idling for a while, the HX and thermosyphon system goes into some sort of a state of thermal equilibrium (WOW! From an art major, no less!) that stops the flow of water circulating through the HX and the brewhead cools. Flushing, waiting, flushing, repeat will get things going again. So, that may not have been caused by the scaling problem but might even be a sign that you have removed enough scale that the machine is operating closer to normal now! or not... remember, this is from an art major!

[Bex]

Thanks Randy - that's very helpful (and said in a way an English Major can understand. )