Buyer's Guide to the Vibiemme Domobar Super - Page 2

Behind the scenes of the site's upcoming equipment reviews.
User avatar
cannonfodder
Team HB

#11: Post by cannonfodder »

Once you have the water reservoir filled and power hooked up it is time to power it on and pull some shots.

The Domobar Super is outfitted with a three position power switch. You normally only find these in commercial machines. In the first (I) position, the system is powered on but the heating element is not yet energized. The pump will prime and start filling the boiler. You can also run water through the heat exchanger and group without engaging the heating element. Given the larger boiler on the Super, the three position switch makes perfect sense. You would not want your heater kicking on before the pump got enough water into the boiler to submerge the heating element.

Once the boiler has filled and you have filled the heat exchanger, you rotate the switch to its final position (II). Once there the heater will kick on and the amber 'element energized' light beside the boiler pressure gauge will illuminate. Now would be a good time to wash out your portafilters and get everything ready. The large boiler and group head take some time to heat. A minimum of 45 minutes is required and an hour is even better.

Image Image Image
Off (0), pump on (I), pump and heating element on (II)

As with all heat exchanger machines, temperature is controlled via the cooling flush. For more information on flushing techniques please read How I Stopped Worrying and Learned to Love HXs. Once heated, I noticed that the machine took less flushing than I anticipated. Both for the initial cooling flush as well as intra shot cooling. A quick email to Jim at 1st-Line answered the question. The Super has a flow restrictor in the upper thermosyphon line. That keeps the group temperature in check even during extended idle periods. My machines idle group temperature stabilizes at 200F give or take a degree. Even with idle periods in excess of four hours the group never got over 202F according to the thermometer fitted into the grouphead.

Image
Group temperature after 4 hours of idle time

Once everything is heated, it is time to pull some shots. I opened up my fresh bag of Ambrosia from Caffe Fresco and dumped it into the LaCimabli Jr grinder. Set my initial grind point, ground and dosed, pulled my cooling flush, tamped locked in and pulled my first shot. The shot was fast, blond, hot and went down the sink. Now the work begins.

As anyone that owns an espresso machine knows, getting the grind/dose/temperature right takes a few tries. The first challenge is getting the cooling flush correct. While the Super's group holds at a nice 200F thanks to the thermosyphon restrictor, the heat exchanger still need to be flushed. One thing I noticed very quickly was how short the flash boil lasted. My Isomac takes around 10 seconds of flow just to get past the flash boil, the Super only required around 3 seconds to reach the end of the flash boil thanks to the cooler group.

I tried several iterations of the cooling flush, flush and go, flush and recover, short flush short recovery short flush and go. Even with the larger boiler, the Vibiemme required some recovery time according to my taste tests. I settled on an initial 10 second flush post flash boil followed by a 10 second recovery for the Ambrosia blend. I find Ambrosia works best for me at around 201F and my tongue is telling me I am hitting the mark. My boiler is set at 1.1 bar at the top of cycle. I learned very quickly (thanks to my grouphead thermometer) that the Domobar Super requires a very short inter shot cooling flush. If you are fast enough on the grind/dose/tamp you can even forgo the intra shot flush. My thermofilter has not arrived yet so I do not have any temperature profiles to post at this time.

Grind and dose; my brew pressure was running a little high so I was grinding finer than usual. I started with a low dose, around 15 grams. I had mixed results at the lower doses. I incrementally increased my dose until I found what works best for Super and my personal taste. I ended up at 16-17 gram depending on the blend I was using.

So far so good, the shots are still developing as I tune the machine and work out what works best for the Super.

Image Image
Tight double ristretto
Dave Stephens

User avatar
cannonfodder
Team HB

#12: Post by cannonfodder »

My brew pressure was running a little on the high side, over 10 bar. I pulled the covers off this evening and made a small pressure change. It is just under 9 bar now. When you change one variable, you have to compensate by changing several others. Reducing the brew pressure required a revisit on the grind and dose settings.

Previously, I was having extraction issues with the higher pressure. I had to grind much finer than normal and was dosing up. I was getting uneven extractions and pitting (channeling) on the puck. I have also changed coffee, which is another major variable change. Right now I am feeding the Super some Black Cat from Intelligentsia Coffee Roasters. I have lowered my dose and coarsened up the grind. With Black Cat, I am dosing 15 grams in the stock double basket and hitting the sweet spot.

Image Image
Ristretto cappuccino bound

I have noted a drop in pressure when the heating element energizes while pulling a shot. An important note to keep in mind, the Vibiemme Domobar Super was designed as a 220 volt machine and then retrofitted to work on 110 volts. The higher 220 voltage requires less amperage than our 110 volte supply. Although the wiring meets UL standards for the required voltage and amperage, the Super suffers the common side effect of a slight dip in the brew pressure when the heating element kicks in. To counter this, I make sure I start my shots at the top of the boiler cycle. I can usually pull a double shot without the heater turning on.
Dave Stephens

User avatar
Randy G.

#13: Post by Randy G. »

cannonfodder wrote:Once you have the water reservoir filled and power hooked up it is time to power it on and pull some shots.

As with all heat exchanger machines, temperature is controlled via the cooling flush. For more information on flushing techniques please read How I Stopped Worrying and Learned to Love HXs. Once heated, I noticed that the machine took less flushing than I anticipated. Both for the initial cooling flush as well as intra shot cooling. A quick email to Jim at 1st-Line answered the question. The Super has a flow restrictor in the upper thermosyphon line. That keeps the group temperature in check even during extended idle periods. My machines idle group temperature stabilizes at 200F give or take a degree. Even with idle periods in excess of four hours the group never got over 202F according to the thermometer fitted into the grouphead.
IIRC, about a year or two ago I read that someone was working on a thermosyphon E-61 with a physical thermostat in the line (bimetallic or?) that would allow or limit the thermosyphon flow based on group temperature. Is this the case here? When originally mentioned it sounded like an elegant and easy solution for the overheating situation. I never heard much about it after that.

User avatar
another_jim
Team HB

#14: Post by another_jim » replying to Randy G. »

The GS3 has a thermoplastic valve to control how the water gets preheated. There's a rumor the same style valve (2 way instead of three) is being used on some thermosyphons, in particular the new Expobars. However, I've heard nothing to confirm this. The Domobar apparently has a built in restrictor that keeps the head from overheating, and the flushes much briefer than on other E61s.
Jim Schulman

User avatar
cafeIKE

#15: Post by cafeIKE »

another_jim wrote:The Domobar apparently has a built in restrictor that keeps the head from overheating, and the flushes much briefer than on other E61s.
Nos 61 and 62 No idea what the difference is between 61 and 62.

I'd be curious to try a Thermoplastic valve on another machine.
My limited experience with them is they have a rather leisurely response.

User avatar
erics
Supporter ◈

#16: Post by erics »

The size of the restriction orifice, located at the boiler end of the upper thermosyphon pipe, is 0.110" (2.8 mm) for this Vibiemme as reported here:

Size of Vibiemme Domobar Super E61 restrictor?

As a matter of interest, the size of a similar restriction orifice optionally(?) fitted to Australian Expobar prosumer machines is 2.5 mm as discussed here:

Installing thermosyphon restrictor on expobar office pulser

I would almost be willing to wager that there exists other prosumer machines with restriction orifices fitted as the above but the only way you would know (for sure) is to do a little disassembly that few of us have undertaken. There are probably a lot of E-61 style machines that don't have them but should have them.

The idea of putting a solenoid valve in the lower thermosyphon line originated here:

An idea for simple temperature control in E61 machines

The only problem I have found here is finding a "proper" solenoid valve that could be fitted and, more importantly, retrofitted to a whole bunch of machines. The idea being to end this cooling flush business for good and at a reasonable cost - say ~ $300. Any help in finding a "proper" solenoid valve would be appreciated.

edit: changed the location of Mr. V's restriction orifice as a result of a PM.
Skål,

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

User avatar
cannonfodder
Team HB

#17: Post by cannonfodder »

I have been thinking about adding a flow restrictor to my Elektra to help control the group temperature. You still need to do a cooling flush because the heat exchanger water is the same temperature as the boiler. However, you are not cooling down a 230F group head which makes the flush shorter.

Think of a washer for a bolt, a plug with a smaller hole in the middle. You essentially have a plug that fits into the thermosyphen at the point the pipe attaches to the grouphead but has a smaller orifice to restrict the flow out of the group, which slows the water into the group, but does not effect the heat exchanger flow during an extraction.
Dave Stephens

User avatar
erics
Supporter ◈

#18: Post by erics »

Maybe these guys can help:

http://superior.thomasnet.com:80/viewit ... &forward=1

MAYBE you could use metal but it better be soft stuff to effect a seal.

Now lets get back to that review, CF :)
Skål,

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

User avatar
cannonfodder
Team HB

#19: Post by cannonfodder »

OK
Dave Stephens

User avatar
cannonfodder
Team HB

#20: Post by cannonfodder »

The Vibiemme Domobar Super really shines as a steamer. One of the defining points about the Super is that Vibiemme has pushed the standard 1.5 liter boiler to 1.8 liters. That may not sound like much, but sometimes big things come in little packages. That extra 0.3 liters must be packed with steam.

The steam wand is affixed to the left side of the machine via a ball joint. That allows you to move the steam wand in any direction needed. The wand itself appears to be slightly larger than most in diameter. I would have to take my calipers to it to compare it with my Isomac. The wand has a small rubber grip point for moving while hot. Just don't miss, or you will be reminded when you sizzle a couple fingers.

Image

The steam is hot and high velocity, though a little moist compared to the Elektra A3.

«missing video»

The steam tip is larger than most and will NOT fit other wand tips. I have an Isomac tip and a Gold Pro two hole tip. The threads on the Super are of a different pitch. While the other tips will start to thread, they bind up after one turn. Personally, I would not recommend changing the tip. It is well matched to the steaming capacity of the machine. It may be a bit fast for a novice user but it creates pitchers of microfoam with next to no effort.

«missing video»

The water tap is a shorter version of the steam wand. It uses the same ball joint, same valve but uses a much shorter wand. The end of the water tap is outfitted with an aerator. I can easily dispense 16oz of water and the flow is still going strong. I dumped 16oz of water into a preheated thermal cup to check the temperature. I measured a solid 208F even with that large draw of water. You will have to watch your hands; she is a fire breathing dragon.

When dispensing water from your boiler you need to make sure you do not dispense too much water. If you flush too much water, you could expose your heating element. An energized heater and no water can lead to a blown heating element. The Domobar Super has a 1.8 Liter boiler, which is 60.883 Fluid Ounces; however the boiler is not filled 100% with water. Assume that no more than half the boiler is full of water giving you .9 Liters. That translates to 30.442 Fluid Ounces. I feel confident that dispensing 16oz of water will not lower the water level below the heating element. Keep in mind that while dispensing water, the pump is replenishing the supply.

Image

If milk based drinks are you preference, the Domobar Super will not disappoint.

Image
Dave Stephens