Valentina brew pressure adjustment - Page 4

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HB
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#31: Post by HB »

Bradley Allen wrote:Again. I'm confused. The pressure runoff is the rubber tube that's connected to the OPV, and normally goes into the rear reservoir, right? Okay. Fine. I pulled that out and put a cup underneath it. I opened the lever, let it run for 30 seconds after pre-infusion and no water came out of it. Weird.
Sorry, I have to ask. Did you have the blind basket in place? The OPV will only open if the pressure exceeds its current setting. If no water comes out of the OPV with the pump running at its maximum, the valve is either set very high, clogged, or otherwise stuck shut.
Dan Kehn

Bradley Allen
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#32: Post by Bradley Allen »

Yes. I had the blind basket in place. Is this desired? Should I just pack a double basket with grounds instead?

I ran it again a few times since my last post. The OPV is now loosened so far counter-clockwise that the rubber tube is beginning to twist. Not too much to cut off flow, but still, this can't be right.

I get consistent approx. 1.5 oz of waste water no matter what I do. And just little drips maybe from the tube connected to the OPV (which always has water in it, though it doesn't come out. I guess a vaccuum has formed in the line). Geez, should I start siphoning and measure the contents I spit out or something? :wink:

Not enough when combined to add up to 2 oz. It's the 'no matter what I do' part that has me worried. Obviously, I'm doing something very wrong.

Complete and utter idiot-proof details, please. Like, step 1: Turn machine on. :)

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shadowfax
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#33: Post by shadowfax »

1.5 oz from where? If you're putting the cup under the backflush runoff, that will get you absolutely nowhere. that's spitting out the volume of the water between where the lever cuts off and the shower screen. basically, the volume of the preinfusion chamber and some tubing in the grouphead. This volume probably is 1.5 oz, and you'd have to re-cast your E61 to get that flush volume to change.

you need to be measuring what comes out of your overflow tube, which is the shorter tube feeding back into the tank. If you aren't getting anything from this with a backflush disk, then you've got a problem. If the pump is still going (it bogs down but continues turning), then you have overflow occurring SOMEWHERE. if it's not out of the overflow tube, then it sounds like your pump is broken or you have a leak somewhere else along the line.

Anyway, I don't have the time or inclination to take my machine apart and run through this again myself. Since you have your machine in pieces, why don't you tell us in your desired level of detail what you are doing, what your results are at each point, and perhaps we can help from there.

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HB
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#34: Post by HB »

We definitely have a failure to communicate. Jim Schulman's Adjusting vibe pump pressure on HX machines explains the mechanics, including the diagram below:

Image
(reproduced with permission)

You should be measuring the water exiting the over-pressure valve, which you've clearly identified. The tubing at the end of the OPV may twist when you adjust, but it's easy to remove, untwist, and replace.
Dan Kehn

Bradley Allen
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#35: Post by Bradley Allen »

shadowfax wrote:1.5 oz from where? If you're putting the cup under the backflush runoff, that will get you absolutely nowhere. that's spitting out the volume of the water between where the lever cuts off and the shower screen. basically, the volume of the preinfusion chamber and some tubing in the grouphead. This volume probably is 1.5 oz, and you'd have to re-cast your E61 to get that flush volume to change.
Well. That settles that, then. Whoopsie. :oops:
shadowfax wrote:you need to be measuring what comes out of your overflow tube, which is the shorter tube feeding back into the tank. If you aren't getting anything from this with a backflush disk, then you've got a problem. If the pump is still going (it bogs down but continues turning), then you have overflow occurring SOMEWHERE. if it's not out of the overflow tube, then it sounds like your pump is broken or you have a leak somewhere else along the line.
Forging ahead... and re-casting myself in a new light, here's a pic of what I think is the overflow tube, which is connected to the OPV adjustment valve:



You can kinda see a bit of water trapped inside the tube. When I pull a shot a little bit of water dribbles out of it. But nowhere near 1-2 ounces.

I don't think the pump is broken. It doesn't run constantly or not at all. It turns on (I think) during pre-infusion and then turns off during extraction. And I don't see a leak. I've handled the machine with kid gloves. Or at least with clean hands.

Now, before I took the hood off the machine, I was making espresso just fine. Okay. It came out too hot/bitter, and looking back, I was viewing the boiler pressure gauge and freaking out over the 1.2 BAR readings. I thought anything over 9 BAR on the meter had to be too hot. But obviously, I didn't understand HX machines. So based on what I've read here, I thought that if I lowered the brew pressure, controlled by the OPV valve (no gauge for that), it wouldn't come out as hot, and I'd have a better extraction.

I'm explaining all of this to make sure I'm on the same page with you guys.

Should I just go out and buy a fancy pressure gauge? If so, sign me up. I want to do this right.

But right now, I'm not sure where to go from here. I can guess at where I had the OPV adjustment valve cranked, put everything back and pretend I didn't touch a thing. Everything will still work. And I'll still be able to extract espresso. It'll just be too hot/bitter. And I feel that would be a waste of what I imagine to be a fine machine. :?

Bradley Allen
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#36: Post by Bradley Allen »

HB wrote:You should be measuring the water exiting the over-pressure valve, which you've clearly identified. The tubing at the end of the OPV may twist when you adjust, but it's easy to remove, untwist, and replace.
The failure to communicate has been all mine. So none of this "we" stuff. :) You guys have been amazing. Thank you.

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HB
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#37: Post by HB »

Bradley Allen wrote:But right now, I'm not sure where to go from here. I can guess at where I had the OPV adjustment valve cranked, put everything back and pretend I didn't touch a thing. Everything will still work. And I'll still be able to extract espresso. It'll just be too hot/bitter.
I'm not sure where you are either. :?

Keep in mind that the OPV determines the maximum pressure during the extraction; the puck determines the minimum. So the OPV not opening isn't an issue for double espressos since the pump flow rate works out to around 9 bar anyway (as explained earlier in the thread). If you're pulling ristrettos (or "accidental ristrettos" as Jim sometimes calls them), it's another story. Then the OPV determines the maximum pressure by venting excess water back to the tank, thereby reducing the overall pressure.

If you don't see a full flow of water coming out of the tubing leading from the OPV when a blind basket is in place, then something's not right. Either the adjustment nut is torqued in way too tight (which compresses the spring), or there's some obstruction.
Should I just go out and buy a fancy pressure gauge? If so, sign me up. I want to do this right.
Although the "runoff method" is a decent estimate, I prefer to measure with a pressure portafilter or install a gauge. Understandably many home baristas don't want to shell out money for an infrequently used tool, but that's what I'd do. Bob explained how you can build your own with standard hardware, quoted below:
bobroseman wrote:It seems to me that if your going to measure brew pressure and make adjustments, then you need to know the exact pressure that you have while pulling a shot. Most portafilter gauges measure only the static pressure at the brew head when the by-pass valve has opened. That is not the pressure you are getting when you are brewing espresso. The attached photo is a simple mod I made to the gauge I bought from Chris Coffee. I can adjust the needle valve to allow precisly 2 oz of water to flow in 25 seconds while reading the pressure. On my machine, the resulting pressure is 8 bar, as seen in the inset.

Bob

Image

here it is in use:

Image
PS: If your espresso is too hot, check your flushing routine as described in How I Stopped Worrying and Learned to Love HXs.
Dan Kehn

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Bradley Allen
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#38: Post by Bradley Allen »

After giving it another try (now that I learned the error of my ways) the OPV was cranked way too far to the right. I don't recall being that aggressive with it. I think it just shipped that way. But either way, I was able to get the runoff tube to expell 2 oz. of water at 30 seconds.

I put everything back and now I'm a happy camper. Thank you. Yay!

Gee, after all was said and done, that was... pretty easy. :lol:

bubba_p
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#39: Post by bubba_p »

Yours is not the only one that was cranked down way too tight. Thanks to this thread, I was able to adjust my Valentina also. Mine also did not have ANY water coming out of the OPV. Thanks to everyone who contributed and thanks for initiating this thread. Too bad I was 1.5 years late in reading it! :shock:

bubba_p
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#40: Post by bubba_p »

Ok, now I've got a new problem. In pulling some test shots with the new OPV setting (drawing 2oz out of the rear tube with a blind filter in) I am getting almost 4oz of espresso out of a shot within 30 seconds. Is this simply a grind and tamp problem (finer grind, heavier tamp) or could I have increased the flow (pressure) instead of decreased it? I remind you that when I started my adjustment of the OPV, I was getting NOTHING out of the tube with a blind filter in. I used a 12mm wrench and turned the adjustment to the left. Anybody have an idea about what gives?