Buyer's Guide to the Vibiemme Domobar Super - Page 9

[jeffg]

Boiler should range from 0.9 to 1.1max. Adjust down if higher. If you don't steam a lot, 0.8 to 1.0 is ideal.
Brew pressure should hold steady. If the brew pressure varies more than ±1/2bar with the heater, it is likely the OPV has the wrong spring.

Sorry, could someone give me more detail on this? my brew pressure repeatedly dips slightly then goes back up while the machine is idle so is this a problem? Or are you referring to when the shot is actually being pulled? etc

[Randy G.]

Sorry, could someone give me more detail on this? my brew pressure repeatedly dips slightly then goes back up while the machine is idle so is this a problem? Or are you referring to when the shot is actually being pulled? etc

These are two different things-

BOILER PRESSURE: This is controlled by the pressurestat. This adjustment is accessed by removing the cup warmer tray. There is a little black plug on the top of the inside, divider panel under the cup warmer. Remove the plug and you will see a large slotted screw. Turn it clockwise to lower boiler pressure. Anticlockwise to raise boiler pressure. This controls the temperature of the water in the boiler, and that controls the brewing temperature as well as the steam reserves. Lowering it means less flushing of the brewhead but less steam. Reading the left gauge (boiler pressure) you can lower this to operate in a range of 0.8 to 1.0 if masses of steam are not a priority. This range will swing up and down-- up as the heating element is energized, and slowly down and the boiler cools. This is repeated many times per hour as the machine idles.

BREW PRESSURE: This is adjusted using the over-pressure relief valve discussed earlier in this review. The pump is capable of at least 14BAR which can blow hoses off in the machine which are not properly secured... I know from experience! The valve opens to bleed water back into the reservoir which lowers brew pressure. A desired reading during the pull is about 9.5 to 10BAR which translates to about 9 bar at the portafilter. It is normal for this to change slightly when the heating element is energized during the pull because the electrical draw of the heating element lessens the amount of current available to the pump.

Now, if your brew pressure varies a lot-- like going up to 12+ bar then back down-- the problem is that the OPV spring needs to be replaced as I discussed in detail earlier in this thread.

[cannonfodder]

Boiler should range from 0.9 to 1.1max. Adjust down if higher. If you don't steam a lot, 0.8 to 1.0 is ideal.
Brew pressure should hold steady. If the brew pressure varies more than ±1/2bar with the heater, it is likely the OPV has the wrong spring.

Sorry, could someone give me more detail on this? my brew pressure repeatedly dips slightly then goes back up while the machine is idle so is this a problem? Or are you referring to when the shot is actually being pulled? etc

That is not a problem. You boiler heat is controlled with a pressure switch (pressurestat). As the boiler cools the pressure will drop slightly. When it drops enough, the pressurestat trips and turns on the heater, the boiler pressure will rise to the pressurestat set point. Once it hits that level, you will hear a 'click' as the points on the pstat open and the heater turns off. Then the cycle repeats.


Pressurestat adjustment


Pressurestat is the large black box marked Parker on the left side of the photo

[jeffg]

Thanks for the info guys. So is back flushing any indication that my pressure stat is ok? When I back flush it hangs at 4 for a few seconds then peaks at 12 or so then i do the flush. When it peaks it stays there and does not fluctuate. Anyway, I have a good barista trainer stopping by the house tomorrow to show me the ropes and I'm sure he'll know if anything is wrong..

[cannonfodder]

That is the brew pressure, not the boiler pressure. Two very different things, and that is normal for a E61 vibe pump brew group. The first raise and dwell is the preinfusion, then it ramps to full brew pressure.

[Randy G.]

A few user observations on the Vibiemme:

The vibration noises come, in a great part, due to a lack of attention to design. The cup-warming tray is the greatest part of it, as has been mentioned in the past in this review. Except for a bit of rubbery weatherstripping [and a "bit" is being kind- there is about a 1" long piece], the entire tray rests metal on metal along its entire front and back edge, and the side edges just sort of float for the most part. Some have recommended electrical tape, but unless they have found some high temperature tape, this is just a stop gap measure. Another unexpected source of vibration is (are) the gauge(s). I will have to open mine again tomorrow, but there seems to be no retainer for the gauge on back of the panel, so the gage sort of floats, and if there is not enough tension holding it in place it will vibrate like crazy, and loud. Louder than the warming tray. More on all that maybe later in the week.

The other annoyance that comes to mind is the very flat bottom of the portafilter body. The Rancilio body drained fairly efficiently after a pull, but the VBM body seems to hold onto a lot more coffee liquid after that shot. it is nearly impossible to remove the portafilter after a pull and get it to the knock box without dripping coffee all over- The bottomless PF works much better in this instance. My bottomless is an old, surplus from a parts box and is not the best fit so I just may pull out the hole saw and bore out one of the two VBM PFs for myself.

[cannonfodder]

I found the cup warmer to be one of the largest vibration culprits (as noted elsewhere in the review). The black PVC electrical tape took care of the issue and has not been a problem since I put it on months ago.

I believe I also noted that part of my vibration noise was coming from a gauge that was not completely seated in the opening as well. The gauges have no mounting bracket, instead they have two (if memory serves) snap in clips. On my machine they were not quite tight and one gauge was vibrating and making noise. I squeezed in the tabs, popped the gauge out and reseated it. It has not been an issue since.

The gauges are chromed plastic not stainless. They are adequate but not high grade. That has been my only complaint with the machine but that is pretty minor of a nit pick. I think it is still an outstanding value given the package you get for a relatively low dollar.

[Randy G.]

I found the cup warmer to be one of the largest vibration culprits (as noted elsewhere in the review). The black PVC electrical tape took care of the issue and has not been a problem since I put it on months ago.

Some of my motivation to make the comments I did was to be fair-- at least to say, to balance out my negative comments made concerning the poor workmanship of the GS3 concerning the grinding of the holes in the frame.

In much the same way, in this case, I think that when someone buys a $1300+ espresso machine, it is somewhat unexpected to have to put electrical tape on a part to keep it from making unacceptable sounds when the machine is operated.

Another possible source of noise is the tray on which the reservoir sits. This can move and come to rest against the case cover. A corner of the tray on mine wore through the paint in one area back in there.

I believe I also noted that part of my vibration noise was coming from a gauge that was not completely seated in the opening as well.

As you did, I removed the gauge by squeezing the clips, pushed the gauge out the front, and used a small screwdriver to spread the clips a bit. It did snap back in more firmly than originally mounted. We shall see how long that lasts. If it repeats the problem I can wedge a bit of closed-cell foam under the clips, and maybe an O-ring under the bezel to isolate the gauge from the face of the front panel.

That has been my only complaint with the machine but that is pretty minor of a nit pick. I think it is still an outstanding value given the package you get for a relatively low dollar.

I do have a fairly long list of other complaints, but they are mainly small ones, and most could have been easily rectified with basic design changes:
- The drip tray that allows water to dribble behind the tray and then under it.
- The flimsy drip tray cover.
- The way the cup warmer scratches the heck out of the painted rear cover.
- The way the face flexes when tightening the portafilter because the brewhead is just mounted to the stainless front panel without reinforcement.
- The overly-difficult access to the OPV
- I even had a thick, dark eyelash behind the lens of one of my gauges (BTW- using a small screwdriver, the lenses can be easily popped out).
- The rear feet placed at the corners making it difficult (if not dangerous) to get to the two screws under the machine holding the inner dividing panel in place.
- We can also add the OPV spring problem that occurred on some machines which I documented previously in this article.
- I had an internal silicone hose come off because it as only secured by one tie wrap. Water sprayed all over inside the machine under pressure. We have all seen tie wraps degrade over time, and so this is not the best of choices for water lines under pressure.

For most of the above, as taken individually, they would seem either nity-picky, or individual incidents not universally found on these machines, but as I mentioned, I think consumers spending this much have a reasonably expectation that they are getting a quality machine that should not have many of those problems.

The works seem to be very well made- boiler, valves, pump, pressurestat, etc, all seem to be of excellent quality. In five or ten years, we shall see how well made it really is. I do not foresee any real problems, and all the parts that really count seem to be of excellent quality.. And the coffee is wonderful as well. Just trying to remain balanced in my comments, and offer a critical (possibly overly-critical..?) point of view for those shopping for machines.

[cannonfodder]

A few I would agree with but have not had issues with many that you list. that is not to say it is not an issue on your machine, just not a problem I encountered.

The drip tray cover is bendable but how stiff does it need to be to hold an 8oz beverage. If you lean on it or place a brick on it, it will bend. However, after several months of heavy usage, it has not been a problem for me. Same for the water behind the drip tray. My drip tray goes completely back against the frame and the 3-way has an extension right to the surface of the expanded steel cover so there is no splashing. Not sure how you are getting water behind it.

On second thought, do you have the drip tray cover on correctly? I noted earlier in the thread that there is a front and back to the cover. If it is on backwards then there would be a gap. I went for a while before I noticed that I had the cover on backwards. There are two notches on the rear portion of the drip tray cover that let it sit flush. Backwards, there will be a gap and the drip tray will not go all the way back leaving a very small gap.

No real issues with the back of the machine getting scratched up. There is a scrape or two on the inside of the cover from pulling the warmer off several hundred times. A little rubber edging on the cup warmer would prevent that, and probably dampen the vibration.

No flexing problems on my unit. You must be yanking that portafilter in pretty hard to do that. People tend to over tighten the portafilters, it does not take much. Twist until the basket contacts the gasket then another 1/16 of an inch on the handle is all that is needed for a seal. My portafilter handle is well left on center when locked in.

Not sure how many machines you have worked on, but the OPV is actually very easy to access. Take off the shell (3 screws on either side) and there it is. Most machine, you take the outer case off, remove the water reservoir, remove the inner housing the reservoir sits on then you can get to the OPV. It takes all of 3 minutes to adjust the VBM OPV.

The OPV spring was an issue but VBM and 1st-Line promptly sent out a replacement spring so a big positive on customer service. Stuff happens.

Gauges, yes a nicer set would be good, but these work just fine.

The feet are not an issue for me. Being on the corners they provide extra stability for the 70+pound heft of the machine. There is no reason a "normal" user would ever need to remove the inner housing since the OPV and pressurestat can be adjusted with it on. I have other machines that are similar in design. Removing that housing is getting into the realm of "qualified technician" not designed to be easily changed by you mere mortal user. But then, how many of us are "normal" users?

The Silicone hose is unfortunate. I have not heard of other issues so hopefully yours was an isolated incident. Wire ties are a very common way of connecting non pressure hoses. It was probably the OPV return line; I think that is the only silicone hose in there that would have any outbound flow. I could have worked loose in shipping or simply not gotten tightened enough at the factory. Again, stuff happens. I have had more than one machine arrive battered by the big brown truck and in need of replacement/repair.

Again, not saying these are null issues, they obviously are on your machine but I have not had similar issues other than those noted.

[1st-line]

I even had a thick, dark eyelash behind the lens of one of my gauges (BTW- using a small screwdriver, the lenses can be easily popped out).

Randy,

This was a personal BONUS for you - many on this fora would have paid extra for this feature!

[kanoyu]

Thanks for the detailed report, questions, and responses. What a project!

BTW, is there any hint of a 'thermosyphon stall' as mentioned here:

http://www.home-barista.com/forum...erature-t3830.html

[cannonfodder]

Neither Dan nor I have had a similar issue, that is not to say it could not happen to someone else but we did not experience it and I tried to replicate it by short flushing my machine long ago just to see if it was a one off instance or an inherent issue.

[Randy G.]

Neither Dan nor I have had a similar issue, that is not to say it could not happen to someone else but we did not experience it and I tried to replicate it by short flushing my machine long ago just to see if it was a one off instance or an inherent issue.

I have seen that once or twice- Since I am new to HX machines it is difficult for me to give any scientific details, but it seemed to happen when the machine was left on for an extended period of time and not used at all-- just idling for four to six hours (since I didn't know it was possible I wasn't timing it). The brewhead temp as reported by Eric's adapter dropped to around 125 or so, and it took a lot of flush- wait- flush to get it back up to temp again. At first I thought the thermometer was bad, but after reading the thermosyphon stall discussion, what happened to me it made more sense.

[HB]

I've not seen this, but I didn't try hard to reproduce it. More to the point, how does a thermosyphon "stall"? Introducing air into the line?

[cannonfodder]

I was thinking something like vapor lock, or airlock. A bubble in the flow restrictor?

[kanoyu]

More to the point, how does a thermosyphon "stall"?

Gosh, I have no idea! I didn't mean to hijack this evaluation, or rehash an old post, I just thought that if it were a design issue (as experienced by another user of the machine in question), then there might be a known, identified fix (for my machine). Clearly it's not a design issue (with the VBM anyway), so I'll drop it. Sorry for the diversion.

[gscace]

I've not seen this, but I didn't try hard to reproduce it. More to the point, how does a thermosyphon "stall"? Introducing air into the line?

A thermosyphon stalls by setting up thermal conditions that prevent it from operating. In normal use the water at the top of the hx is hotter than the water at the bottom of the hx. Water in the group cools and sinks down, being replaced by the less dense, hot water from the top of the hx. It's possible to have a situation in which the water in the hx is cooler than the water in the group. This can occur if the hx volume is small, as in small home machines and if the hx has been overly flushed, with the metal of the group heating the water within the group to a high temperature relative to the hx. Another possible cause is related to the geometry of the hx water inlet. E-61 systems usually have the water returning from the group re-entering the hx at the same point as water from the pump. The plumbing layout is such that flow to the group during brewing gets split between water that never actually enters the hx and water that flows from the top of the hx. Good brew temperature control requires extablishing the correct proportion of water from each source. It's possible to screw this up so that you stall the thermosyphon.

Good e-61 machine setup establishes enough thermosyphon flow to get the group temperature to idle at the desired brew temperature. The proportion of cold and hot hx water mixing must also be adjusted so that the right brew temperature is achieved. If done right you can set up a system that requires little or no flushing at all over a wide variety of duty cycles.

-Greg

I wrote a couple of pieces on this subject a couple of years ago when i was learning how to tune my Astra. They are on Alt.coffee and might be worth a look.

[cannonfodder]

More to the point, how does a thermosyphon "stall"?

Gosh, I have no idea! I didn't mean to hijack this evaluation, or rehash an old post, I just thought that if it were a design issue (as experienced by another user of the machine in question), then there might be a known, identified fix (for my machine). Clearly it's not a design issue (with the VBM anyway), so I'll drop it. Sorry for the diversion.

That is not slight at your question, but rather another question, which Greg answered quite nicely. Don"t take it as an insult.

Thank you for that info Greg.

[Randy G.]

Taken on their own, my previous comments about the Domobar might be interpreted as my not liking the machine. That is not the case. A couple of days ago I did the electrical tape "fix" for the front edge of the cup-warming tray and that really quieted that down a lot. I also remounted the brew pressure gauge to eliminate that rattle as well. While I had the case apart I dropped the brew pressure by adjusting the OPV about .2 bar, down to an indicated 9.6 or so.

This morning my wife walked by as I was pulling a double and she actually stopped and said, "That sure sounds different this morning!" I explained why, and she stated that it really was a lot quieter.

While we were sipping our morning cappas she talked about how much smoother the coffee had been since the VBM arrived, and that the morning drinks were so much more consistent now. "Except for that one morning, they have been really good every time." 'That one morning...' I'll never hear the end of that one....

So, yes, as stated by others, many of the things I was commenting on seemed to be anomalies on my machine for whatever reason, and Jim was really great about the spring replacement for the OPV [and what an amazing difference that made in the machine's performance!]. But on its own merits (since I do not have experience with other HX machine to which I could compare) the performance of the machine is exceptional.

[cannonfodder]

Neither Dan nor I have had a similar issue, that is not to say it could not happen to someone else but we did not experience it and I tried to replicate it by short flushing my machine long ago just to see if it was a one off instance or an inherent issue.

Well, I have to take that back. I drained the boiler Friday so I could take the machine back home for a final set of test and measuring but I left it in my office. So today I powered it back on and let the pump prime up the boiler. It has been on for 6 hours and I am just getting a chance to pull a shot. Luke warm group. I can put my hand on the group for 3 seconds before it get pull your hand off hot. It appears that I have experienced a thermosyphon stall, or failure to prime after dumping the boiler.

I am going to run some back flushes to see if I can prime it and get it hot before I shut down for the work day.