Valentina brew pressure adjustment

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James

#1: Post by James »

Today I got a pressure gauge to measure my brew pressure on my La Valentina, and I concluded that my pressure was to high (12 bar) and I would like to reduce the pressure to approx. 9 bar. The problem is i can't figure out how to lower the pressure, I have open the Valentina but I don't think it is so simple to figure out. I have taken a couple of photos and thought that some of might where able to describe it for me, the pictures are on my website:

http://www.james.dk/side1.jpg
http://www.james.dk/side2.jpg

Hope someone can help me ;-))

Brgds
James

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malachi

#2: Post by malachi »

From Dan's excellent "Buyer's Guide to the La Valentina"...

"The expansion valve, which determines the maximum brew pressure, was initially set at 12 bar (this valve is also called an over-pressure valve or "OPV"). If the pump is unregulated, it can produce an overextracted, bitter shot. Adjusting it down to nine bar helped the consistency of my shots immensely, especially when pulling ristrettos. You'll need a portafilter pressure gauge to adjust it because there is no brew pressure gauge. I recommend asking 1st-line to do the adjustment before shipping.

Valentina's expansion valve is an industrial-grade fluid control valve, rated for two years of continuous use. That translates into forever in a home environment. The expansion valve allows for very fine adjustments. The one-bar adjustment of some non-commercial expansion valves corresponds to a slight turn of a small screw; Valentina's is finely adjustable and is done simply by turning the end of expansion valve itself. This means that you have a lot of control without fear of overshooting the desired maximum pressure by a slip of the pliers."
"Taste is the only morality." -- John Ruskin

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HB
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#3: Post by HB »

The Andreja Premium has the same expansion valve as Valentina. FAQ #13 at http://www.chriscoffee.com/faq has a good picture of it:

Image

(image courtesy of Chris' Coffee Service)
Dan Kehn

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shadowfax

#4: Post by shadowfax »

Dan, I brought mine down a bunch the other day. I have it flushing out 2 oz of fluid in 37 seconds (incl. the "preinfusion" ramp up...). That is, it's flushing out 2 oz in 30 seconds after the pump bogs from being at full pressure. Is that the right measurement as Jim describes to get the 8.5-9.5 bars, or should I be getting 2-2.5 oz within 30 seconds of the beastie turning on?

By the way, the pump on Levetta is the EX5, the same as the one Jim refers to from the Isomacs and others... I understand yours is the EP5, with a plastic barrel thingy? but they are otherwise the same pump, I assume?

I am too cheap to buy a special PF for this, and I don't feel like tinkering to the point of installing my own brew pressure gauge just yet. I like the pressure runoff measurement idea for getting in the ballpark, though.

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HB
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#5: Post by HB »

Jim's "runoff method" assumes the system is fully pressurized, so you'll need to wait until the expansion valve (OPV) overflow tube is running steadily. Then you can indirectly calculate the effective brew pressure:

Image
(image courtesy of Ulka S.p.A.)

So 100cc / 30 seconds ~ 10 bar, 150cc / 30 seconds ~ 8 bar. According to the Ulka website, the EX5 pump is one minute on / one minute rest. Keep that in mind when testing the brew pressure.

Your Levetta has the EX5? Mine has the EP5, which like you said means the barrel is plastic. Oh well, must have been out of stock the week I ordered. :?
Dan Kehn

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shadowfax

#6: Post by shadowfax »

yeah, has the pretty brass thingy. It is $100 more than the one you have, so maybe that's one place they spruced it up, other than the full E61 group.

I'll shoot for 125 cc in 30, I guess. I understand that having the OPV set right at 9 bar makes your shots tend to brew a little bit lower (like 1/2 bar less), though, so I don't want to shoot any lower.

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shadowfax

#7: Post by shadowfax »

just in case the original poster is interested, here's a shot of where it is on my valentina... Just beside the Gicar flowmeter thingy.

Image

Thanks, Dan. I've got it all up and running at about 2.2 oz/30 seconds. I think that should put my shots around the high 8/low 9 bars for brewing. Maybe someday I'll check for real.

and just for kicks:

Image

as Chris would say, she's getting all bauhaus on me!

James

#8: Post by James »

Thank you for the reply, I have now managed to reduced the brew-pressure, although it seems the European model is a bit different from the US-models.

James

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shadowfax

#9: Post by shadowfax »

Well, I would guess. I think they can put much higher-wattage toys in European espresso machines because you guys have 220 V connectors. What's different about yours?

James

#10: Post by James »

The things I have noticed so far is that my boiler is copper or something that looks like copper, and my "Gicar flowmeter" and my OPV is not on the same side of the boiler.

James