I have a Wega Lyra (aka: Wega Mini Nova) single group HX machine. Mine has the built in water reservoir with a vibration pump.

My question: If I want to reduce the pressure out-put there seems to be two places to do that. Which valve do I use?

There is a pressure reducing valve located at the discharge end of the vibration pump. It "dumps" to a clear tube that ultimately leads to the drain pan. There is also a reducing valve located on the copper tubing leading into the boiler. This line feeds the heat exchanger and ultimately out through the portafilter. The "dump" from this this valve feeds back to the intake side of the vibration pump.

Which valve should I adjust first? only? partially?....

When I loosen the valve at the discharge of the vibe-pump the "dump" or diversion of water to the drain is obvious. When I adjust the valve on the copper tubing the effect is not so clear.

If ultimately I want more water volume but less pressure which valve should I be fiddling with?

thanks

Page 23 of this link shows the basic water system for a Wega Mininova even though it shows direct connect whereas you said you were drawing from the tank. Does this represent your machine?

http://www.coffeeworksexpress.com.au/We ... 0parts.pdf

I really wouldn't make any changes to the relief/regulating valves WITHOUT knowing where you currently stand. I can readily explain the drawing I referenced but your description is not tracking too well with that illustration. There's probably upmteen different ways to measure "brew pressure" but the BEST way to do it is by means of a portafilter pressure gage (use a gage that is oil filled) and a bleed valve or fine orifice to simulate the actual flow YOU desire - say 1.75 ounces in 25 seconds for discussion purposes.

Do a search on this site for "measuring brew pressure" and various systems will be revealed.

Hello Medic One,
I had a similar question that I posted less than a day before you did. I wanted to know why two pressure regulators on the Wega.

See my post: Pressure regulators: Why two pressure regulators on E61?
(for details regarding which pressure relief valve I am referring to in the following...)

Another_jim confirmed my conclusion that the lower pressure relief valve [PR2] is a safety relief valve in event of an over pressure condition in the thermal siphon circuit while the upper pressure relief valve [PR1] is used to set the working shot pressure. I agree with Erics in that I think care should be taken to adjust [PR1] so that you have an appropriate shot pressure AND flow rate since vibe-pump flow rates are pressure dependent. Also note that Another_jim suggested that [PR2] should be set to something like 11bar. Can someone confirm this setting for [PR2]?

trzynkaa

Andrew -

I would think your PR2 should be set to around 12-13 bar as it is designed (as you say) to release any excess pressure in the thermosyphon system, primarily due to thermal expansion of the water. All that would take is a dribble or two. The manufacturer, Wega, should be a good and willing source for this setting as it is safety related. PR1 couldn't do this because the check valve CV1 prevents it from seeing the excess pressure.

PR1 is the typical OPV designed to limit the maximum pressure during espresso production. Note that the pump shown in your pic is a Fluid-O-Tech 1106 which has a different (read better IMO) capacity curve than the usual Ulka. See below:



Keep in mind that my "curves" are based on mfg data and this data represents production averages and as measured AT THE PUMP DISCHARGE fitting.

Wow! It looks like the Vibe pump puts out significantly less volume at the normal pressure point. Does that throw off the whole rule of thumb about 2oz. of espresso at approx. 25sec?

The reason I started making adjustments was that I was getting a large volume of (unpleasant) espresso for the given 25 seconds. I like the tast and color of what I'm getting now, but it's not 2 oz.

I'm assuming that "PR2" is the upper valve. Here is a picture from my machine. Is the valve in the circle "PR2"? Please note the white discharge hose leading downward on the left of the PR.


Here you can see where the white discharge line feeds back into the intake side of the pump. ("From the pressure relief")


Here is a photograph of the other "PR" that I was referring to. You can see it's immediately after the vibe pump. Obviously the silver reinforced water line is under pressure, but also note the clear tube leading off to the right with the blue zip tie. This is the "dump" from the relief valve. It leads to, and taps into, the drain line ending in the drip tray.


So which valve should I be tweeking?
Thanks

Zachary -

Your machine is DIFFERENT. Are you the original owner? Do you know whether the vibe pump has been replaced at any time?

The vibe pump configuration you have has the typical OPV "factory mounted" to the pumps output. Under any other circumstances, you (reluctantly) should be adjusting what you show to be PR2. Note that Andrew designated this valve as PR1 in his sketch (in his referenced link).

If you like the taste and "color" of what you're getting now, time to take a break and figure out a way to measure the actual pressure before you make any other adjustments.

After the technical pressure (about 9 bar) at flow rate (about 2 oz in 30 seconds) is set for your Lyra, adjust your extraction volume by tweeking your grind and tamp.....
Andrew

Thanks Eric,

I am not the original owner. Yes the pump was replaced by Espresso Parts NW. In fact I was able to speak with Terry Z. who informed me that he was involved in the design of this machine. I tried to re-contact regarding the issue we are discussing but I never received a reply.

In looking at all the photos invovled in this post I notice that I actually have three pressure valves:
(1) The upper most valve I mistakenly referred to as "PR2", which Andrew called "PR1"
(2) The lower valve which is located at the bottom of the boiler, is the same type as valve #1 and named "PR2" in Andrew's post
(3) The pump mounted valve which I will call the "pump PR" and does not exist on Andrew's machine.

I have never touched what Andrew calls "PR2". I have adjusted the upper most "PR1" (Andrew's label). I have also adjusted the "pump PR".

I appreciate that using a pressure-portafilter would be ideal, but I'm just not willing to fork out the money for that devise. So can anyone tell me what adjusting each should accomplish?

It seems like the upper most "PR1" and the "pump PR" are redundant. If I really open up the "pump PR" then the "PR1" never receives the required pressure regardless of its setting. Conversely, if I tighten down the "pump PR" and direct the full pressure of the pump to "PR1" then its valve is regulating all the pressure.

So does it really matter which one I adjust?
Should I just stick with the "PR1" for my tweeking?
Will either affect volume more than the other?

Thanks

I have never touched what Andrew calls "PR2"

That's good - lets just assume that valve is set correctly. There's a correct way to do it but that would require a pressure gage assembly.

Conversely, if I tighten down the "pump PR" and direct the full pressure of the pump to "PR1" then its valve is regulating all the pressure.

That seems like a good plan because it then takes a pressure relief valve out of the system that was not in there in the first place.

Should I just stick with the "PR1" for my tweeking?

Yes

There are a few threads about this over on coffeegeek so a search over there may be helpful. I happen to have adjusted the pressure on my Mininova just last week and agree with Eric about always adjusting the valve up by the top of the boiler.

I highly suggest a gauge, you can get the parts to make one at Lowes for under $10. You'll need the gauge they sell (which reads PSI) and an adapter to make it fit the PF. I know the thread pitch is different on the Wega PF than the adapter they sell, just use a bunch of teflon tape and thread it on enough to seal but not to destroy the threads. I can lookup the exact fitting tonight when I get home if you're interested.

~Michael