Hi Garbage,Originally Posted by garbage link=1222763750/0#0 date=1222763749
I can email you a more comprehensive manual if youd like to make contact.
Id like to adjust the brew pressure setting on my VBM Domobar Super. Im a bit confused by the seriously deficient instruction manual that comes with the machine. It talks about adjusting the "pump pressure setting" - I assume this means the brew pressure. To increase the pump pressure, it says to turn it clockwise and to decrease pump pressure, to turn it anti-clockwise. Now, Im looking at what Im guessing is the pump pressure valve just under the lid near where the right hand gauge is, and the indicators next to it suggest it is the complete opposite - anti-clockwise to increase / clockwise to decrease. Can someone please clear my confusion on this one? Am I looking at the right valve to set the brew pressure at ~10.5 on the built-in gauge? This gauge came shipped at about 1 oclock.
Hi Garbage,Originally Posted by garbage link=1222763750/0#0 date=1222763749
I can email you a more comprehensive manual if youd like to make contact.
Thanks for that! Its just what I was after!
Could also get a copy of your more comprehensive manual Chris? Ive only seen RandyGs before.
garbage, another option is to download the manual that Randy G. wrote for it for 1st line, link in this thread http://coffeesnobs.com.au/YaBB.pl?num=1207665514/4 - it is also quite comprehensive.
Hi Sammus,Originally Posted by Sammus link=1222763750/0#3 date=1223084388
There is no more comprehensive manual that the 1st line one....grab it ;)
Thank you, Chris. Very kind of you to say that.Originally Posted by 2muchcoffeeman link=1222763750/0#4 date=1223084764
The direct link to the manual is:
I wrote it, cover to cover, 1st Line now owns it, and Jim at 1st Line has been very kind to post it for use by anyone who desires to read through it. I think it works as a sales carrot as well as an operators guide. After owning my VBM DS for about 16 months now, I could not imagine going back to Silvia... I really think that I would rather just use the Aeropress! When paired with a good grinder the DS is an amazing machine.
As I have previously said, its built nearly as tough as my 240 Volvo! ;)
I am quite proud of that manual, and I do feel that it is a very comprehensive guide to using that machine. I feel that writing manuals is NOT the same as show business- you should leave your audience wanting nothing.
You have probably already worked it out from the 1st Line manual but, no, the valve you are looking at is the boiler pressure valve. This is associated with the gauge on the left. Getting the boiler pressure right is an indirect way of getting the right boiler temperature and in turn, the right brew temperature.Originally Posted by garbage link=1222763750/0#0 date=1222763749
The brew pressure is set by an adjustable pressure relieving valve awkwardly located at the back of the machine. For some reason the term over pressure valve (OPV) has crept into coffee terminology. Perhaps itís an Americanism. You are best to turn the machine around. Take off the SS cover by removing the 3 screws on each side. The OPV can be accessed through the square hole towards the bottom left. The valve and access hole are very poorly aligned. Itís not something you want to do too often. Youíll need a very broad headed screwdriver or risk damaging the slot on the adjusting screw. The adjustment is not very sensitive. You may have to turn the screw a full turn. Try a quarter of a turn at a time. As I recall, anti-clockwise reduces pressure.
The conventional wisdom seem to be that 9 bar at the group is optimum. I got myself a group pressure gauge but Iím not sure Iíd recommend that considering the cost. With the vibrating pump, the gauge jumps around like a mad womanísÖ. I set the valve to give an average of around 9 bar on the group gauge. This translated to exactly 10 bar on the right hand gauge of the Domobar using a blank basket. It drops a bit during an actual brew and varies slightly during the day. Iím sticking with that for the time being until I get the myriad of other brewing variables reasonably consistent.
Damn, so I guess Im not the first person whos coffee machine is as expensive and bulletproof as the car they drive! ;)Originally Posted by Randy G. link=1222763750/0#5 date=1223098697
This may be a silly/obvious question, but I take it that if I pull a shot and my brew pressure needle, after sitting at around 6bar for a while, then shoots up to 13.5bar and tops out, Im using too high a pressure and need a coarser grind?
I need to get a handle on how to do the whole grind adjustment thing, as its not really clicked with me yet..
It sounds like either the gauge is inaccurate or the OPV needs to be adjusted or the spring needs updating. A choked shot should read about the same as when you use the blind basket to backflush. There is virtually no difference in this context. The pressure should really not go over about 9.8 during a pull, and certainly never over 10. The grind is not the problem.
Access the OPV and unscrew the adjustment screw and remove the spring and piston and examine them. Go here:
and compare the spring you removed with the image there. You may have the old spring.. if you find the pressure varies- tat is, sometimes it seems OK and other times it is high, even when using the same grind, this is a symptom of a machine which has the wrong spring in it.
While you have the spring out, examine the bore for crud and check the piston for damage. *If it looks abit dirty, put a bowl under the valve (or slide the machine over the sink, and CAREFULLY run the pump for about 1 or 2 seconds to flush the valve out.
WARNING: electricity and water mix quite well and can kill you! :o
If all is well, reassemble. Install the blind basket (as if you are backflushing) and when pressure settles, adjust the OPV to get a reading of about 9.6 to 9.8. At that point I think you will be a much happier home barista.
I did the adjustment this afternoon and its reading 10 on the gauge now. Still needs to be turned down a smidge, but already the results are much better, with almost no bitterness and more consistent shots!
I wonder why it would have been adjusted so high - had to wind it back over half a turn... Surely they would pay more attention to this at the factory?
BTW, everyone that says the cutout is a pain in the a$$ because it doesnt line up with the adjustment screw is right! It should be cut about 10mm lower so the screwdriver can line up properly. :P
Two flathead screwdrivers side by side gives reasonable leverage.
Very cool to hear that! Sometimes there are simple solutions to big problems! If you find it wandering you should remove the spring and piston and check as I recommended earlier.I did the adjustment this afternoon and its reading 10 on the gauge now. ... the results are much better, with almost no bitterness *and more consistent shots!
I was one of the first. I did loosen the fittings on the valve and rotate it just a bit to put it at a better angle, but still... *How cool would it have been to place it up top where it would be accessible under the drip tray like the pressurestat...? Or at least behind its OWN access opening instead of using the hole formed by the cut-and-bend made to form the mount for the water level switch...BTW, everyone that says the cutout is a pain in the a$$ because it doesnt line up with the adjustment screw is right! It should be cut about 10mm lower so the screwdriver can line up properly. *:P
Oh, well.. a small price to pay for the six weeks (and counting) of daily great espressi without a single bad pull! From my own experience, pairing this machine with a quality grinder makes an awesome setup.
I need some technical advice.
I reduced the OPV pressure yesterday to 10 bar (from supplier-released 12 bar) with a blind basket, which according to Randys work means it should be at 9 bar at the group.
The first shot today with a slightly coarsened grind was a magic shot - perfect taste, length to blonding, and time 8-); and every other shot following was sour. My dose/distribute/tamp technique is consistent. Ive only once had sour shots before since Ive owned the VBM and could directly attribute it to too much flushing prior to the shot. Can someone please explain the physics of reducing the OPV pressure?
On the basis that the first shot was fab, and my repeatable consistency in pulling shots, I assume that it has to do with temperature - is it best to work with the boiler pressure and up it from its current 1.1bar to 1.2 bar to get that extra degree celsius constant, or to change the OPV back up a little?
I was pretty astounded at the change in crema from a 12 bar to a 10 bar setting: its surface viscosity was more homogenised, particularly evident when pouring latte art. With the setting at 12 bar the crema surface was slightly tougher - perhaps a few more fine oils collecting on top more rapidly, with it at 10 bar the crema surface was more silky and gorgeous to pour into. Even with the sour shots.
I also am thinking that temperature is an issue. My Pstat setting turns on the element at about 0.85, and OFF at about .955, and when the Pstat clicks to OFF the gauge snaps the short distance and reads just a tiny bit over 1.0.
I have Erics thermometer adapter and it is really a big plus to be able to flush to exactly the same point every time. I always flush to about 203.5 F. for the first pull when the machine has been idling. If it has been idling for an extended period I will flush to about 203 F., grind, dose, tamp and before locking the PF in place I flush again to 203.5 F. For consecutive shots I just flush a tiny bit before the pull to be sure the machine is up to temp and to clean the screen.
All I can say is that on my machine with my grinder and water and the coffee I use, my settings work.. I would recommend that you try the same thing again tomorrow and see if the first shot is good again and the subsequent pulls are again sour. If that is the case then it sounds like the temperature is too low. Set the Pstat a bit hotter, but be aware that you will need a longer flush for the first shot because the machine will be running hotter. Without the brewhead thermometer it is going to be a guessing game as to the actual temperature and the flush time needed.
Remember that the OPV setting is merely the adjust to limit the maximum allowed brew pressure. Anything below the set pressure is still possible by adjusting the grind. The valve is not binary, so it can go from dribble to a flow. If you have any doubt as to w it is working, you can remove the return hose from the reservoir and place it in (or over) an external vessel during a few extractions to watch its function.
At no time should the machine need to be running that high of a pressure. Adjust the OPV. Use a blind filter, run the machine, and set the OPV to allow no more that about 9.8-10 BAR (assuming you have a VBM DS). This will make it easier to find the correct grind as well as will be subjecting the machine (particularly the pump) to less stress. Now if you grind too fine the flow will be barely a dribble or to get a double it will take 35 or more seconds.
Thanks Randy for the quick response.
At 10 bar I did a 60ml flush for the first (magic) shot after 1.5hrs of preheating, and none for the subsequent (sour) shots.
At 12 bar I was able to do back to back milk-based shots without flushing in between, so perhaps my machine does run a little cooler.
I thought the OPV valve only affected the brew pressure, and therefore wouldnt have had anything to do with the temperature dropping which I thought was regulated by the pressurestat, but as its the only change Ive made its obvious it does in some way.
EDIT: Actually I thought the brew temperature would increase as the brew pressure line going through the heat exchanger is running at a slower pace?
EDIT2: My first shot this morning was sour after a 60ml initial flush as usual.
Youre making me dizzy.. ;)
Just to clarify for all newbies (not necessarily you at all):
PRESURESTAT: a thermostat that reads pressure in the main boiler to control water temperature. Since water, heated in a sealed chamber, will be at predictable temperatures for any given pressure, this is a dependable and inexpensive way to judge temperature. This Boyles Law iirc, but dont go by me- I was an art major. if you are on a private well, that little gray box on the well head works as a pressurestat to control the pumps on and off cycles to maintain pressure in the holding tank.
Pressure Relief Valve (Overpressure Relief Valve or OPV): a pressure regulator that control brewing force. Usually located between the pup and the brewhead. Spring pressure against a piston is the mechanical method- when pressure rises and pushes against the piston, the spring is compressed a bit and water is allowed to bypass the piston, usually going back to the reservoir.
Water is pumped into the heat exchanger and the incoming cold water displaces the hot water in the HX. For the most part, the speed of this movement will have only a small effect on the brew temperature if any at all. This is particularly true of the massive E-61 on the VBM DS machines. This is also controlled by the volume of the HX as well as the design of the water injector inside the HX. Its part of what you pay extra for- one of the hidden bonuses... at least when it works correctly.
Without a way to accurately measure the brew temperature on your machine we are going to have to engage in a guessing game. I guess that your pressure gauge is not accurate. Just a guess. Best tool to check is a Scace device... very expensive for a home barista. Next best is probably Erics adapter and the digital thermometer option. if you have a DMM with a thermocouple, or any sort of thermometer, you might try to rig in a way to check the brew temp using the EPS takeaway cup method as I describe on my website. Not accurate, but it should give you an idea as to what is going on....
But... the bottom line is that whatever tastes best to you is what is best, so the palate is the final arbitrator in this debate. You may need a higher boiler pressure setting and a longer initial flush....
Further experiments. More dizziness.
I tried racking up the OPV by about a bar and ended up with bitter and sour shots.
I tried reducing the OPV back to just under 10 bar (read "just under 9 bar") and have sour shots.
I tried upping the pressurestat to just under 1.4 bar and have sour shots.
The pressurestat at just under 1.4 bar is producing water temperature coming out of the group and naked PF/basket at 95-96*C, measured with the tip of a DMM flexible probe. When I pull a shot with the same naked PF/basket, its producing coffee at max of 84*C.
I measured the temp inside the grouphead near the gasket seal right in front of the 3-way valve tube and its at 93*C when idling. Obviously, this isnt right inside the grouphead, but the only way I can get some kind of measurement without Erics probe.
The machine is about 4-5 months old and on average has pulled 6-8 double shots a day, is supplied with filtered water with a Brita on-tap.
EDIT: After idling for 2 hours, group temp is at 95*C when idling. 60ml flush = 99*C. next 60ml flush = 98*C. Shot 1 was 97*C by end of shot. Shot 2 96*C by end of shot. Seems all too hot.
Will reduce temp back to 1.2 bar, increase pressure to 10.5 bar (equiv 9.5ish), allow to settle for an hour or so and see what happens.
Well, I am wearing out a keyboard at this end! * ;)Further experiments. More dizziness.
You have got so much going on and are working against so many variables that I just dont know what to tell you.. I think that you need to become more familiar with the machine. As Samuel Clemens said, "First get your facts straight.. Then distort them all you like."
When I had my VBM DS for about 10 months or so I switched from Rocky to a Mazzer Kony. it took me a few weeks to get things working right. I actually had to adjust my blend a bit and roasting style to match my new set up. the grinder was bringing out flavors from my older blend that i didnt like. A small change in blend made a difference.
Applying this to your situation, the first thing is to become consistent with what is happening. Set the OPV and pressurestat to some given known values that work 9based on the recommendations of others) and then see if you can make the coffee extract the same and taste the same, time after time. Then change one thing, a little at a time, until you begin to close in on what works. That means, change the pressurestat by .1 bar and leave it there for a day or three, then change it about that much again and see how that affects your coffee.
As far off as your brew pressure settings and pressurestat settings seem to be, and a wide as the taste results seem to be, I would say that you are having difficulties in other areas: grind, distribution, dose, or even the coffee itself. i dont know.. *
After all that, my first proposal would be to try another coffee.
My next would be to get a barista with skills to drop by and see what they can do.
Additionally- what grinder and what beans are you using? Espresso is water and coffee, and most of the taste comes from coffee. The VBM responds to a quality grinder. The "low end" espresso grinders like the Rancilio Rocky will give inconsistent results. I really like my Mazzer because of the stout upper burr mount that holds the burrs in precise and solid alignment. Being stepless is also very cool.
So the bottom line is that there are lot of things that all have to work together to make good espresso, so you need to look at all of them. trying to adjust one or two things while thee are problems elsewhere is an exercise in futility and frustration.
And to make you feel even worse, I have gone over five weeks, a minimum of two doubles a day, with excellent results every pull. With my home blend and home roast I can get well over two full ounces of crema before espresso starts to settle out.
But to make you feel better, I had a Silvia and Rocky for some 6.5 years and struggled with that day in and day out trying to get consistent results, and I have had the VBM for 15 months and the Mazzer for *about 8 months or so. A home barista generally just does not make enough espresso on a daily basis to get good in a hurry. if you had this equipment and were working in a coffee shop, you would probably pull 50 or more doubles a day, and you could get things tuned in quickly.
So patience will rule out if you allow it to. Get back to basics and work from there. Thats my advice.
I give up for today. >:(
Grinder: Macap M4. Same age as VBM. New.
Beans: Espresso Wow - Andys. Been using them consistently for 4 months, purchased weekly. This weeks is a slightly lighter roast. Prior roasts tasted great at 12 (11) bar, ristretto.
DDT: Refined method, worked at 12 bar (11). Figure it should work at 10 (9)? Updosed, 17g double, NSEW dist, level firm tamp, custom-fitted Pullman tamper.
Tiger-striping: beautiful in each shot. Figure the DDT is ok?
Grinder: refining grind for each OPV pressure change to get double poured in 30 secs.
Thanks Randy. ;) Appreciate you wearing out your keyboard.
Dug out a month-old batch of of the same blend, roasted about 1-1.5 CS darker. Roughly adjusted the grind for the older beans. Flushed the machine to 93*C temp out of the group. Ran the shot straight away. Quicker shot to blonding. Tasted great. Slight acidity, no sourness, lovely sweetness, but less complexity than in its prime. My machine obviously doesnt like the lighter roast of this blend for espresso. * :( Off to work it goes. <EDIT: I have no idea how the magic shot happened. I had a sip and my husband drank the rest, so perhaps I didnt assess it correctly.>
My favourite roast level of this blend at 11 bar was between the two roast levels Ive had today. Seems like itll be true at this 9.5 bar level too.
Im going to drop the pressurestat down a little more again as the water temp coming out of the group is too high, needing too long a flush. Back to the original Di Bartoli setting *;).
Tenacity. Not to be confused with patience. ;D
The roaster advised the batch was roasted within its usual tolerances, however has kindly replaced the beans :) :) :) Great service yet again.
Does this apply for rotary VBM DS?
fraid not.Originally Posted by 6A687E79776864790D0 link=1222763750/23#23 date=1288476610
Rotary pump VBM machines dont come to Australia.
Rotary pumps have an inbuilt bypass adjustable via screw.
Reviving this thread as I have recently bought a used version of this machine.
I've read through the posts, and I wanted to confirm I'm understanding the details correctly - before adjusting my machine.
Current operation / status:
When I pull a shot the right gauge (brew pressure) shoots up to 13 and stays there
When I place a blind filter in, same behavior - the brew pressure gauge shoots up to 13
I get more volume than targeted. I dose 18g and I'm aiming for a 30g shot in 30s
Grinding done with a Mazzer Mini (running it around 6-9 notches up from locked, notches = the little grooves on the adjuster, NOT the numbers)
I usually get close to 40-45 grams of espresso in 30 seconds.
I can't remember the exact reading on the left gauge (boiler pressure), but I recall it being around 1.2-1.3 (will check when I switch her on tonight)
What I've been done:
- Ground finer and finer - Starting to get some "grittiness" in the cup
- Taste comparison - Have been using Talk-Coffee's P2 blend. Chris made me a shot last weekend which tasted "almost" the same, but with no grittiness in his cup
- Backflushed the machine a lot (definitely clear water coming out now)
- Checked mushroom for scale (not much)
What I think I need to do now:
- Adjust the OPV to reduce the pressure (anti-clockwise turn) down to 10 bar at the dial (to get 9 bar at the group), when doing a blind flush
Does that sound right?
Do I need to adjust the boiler pressure? (Will confirm reading in a few hours)
Should I be adjusting anything else before messing with (what I assume are) factory settings?
Edit: Found answer to question here: https://www.espressocare.com/assets/...leteManual.pdf
Can adjust OPV whilst machine is in operation it seems.
Thanks in advance
Last edited by davidxcoffee; 5th October 2016 at 03:02 PM. Reason: Answered one of my questions by finding the answer on Google
I'd suggest 10.5Bar at the gauge (assuming it's working correctly)
Just fixed it up tonight. Thanks Chris and randy g. Shots coming through nicely now and crema is much more golden brown than dark like before.