RichardMoulton Senior Member Joined: 19 Aug 2010 Posts: 27 Location: Oakland, CA Expertise: I like coffee
Posted Tue Aug 31, 2010, 9:22am Subject: Re: anyone measure pressure on non-solonoid machine?
The test fixture was simple, an elbow on the bottom of the portafilter and a gauge - I didn't put a release valve - so I couldn't adjust the flow that easily.
Using the PF without a basket would make a tight seal so I was reading pressure without any flow. To get some flow, I could either loosen the pipe fittings a little to let them leak - or I could insert the basket with teflon tape around it to limit how much leaks around the basket to PF seat. A small tupperware underneath the PF to capture the leaking water and measure the amount of liquid flowing in 25 seconds. A needle valve would be much more elegant and adjustable.
RichardMoulton Senior Member Joined: 19 Aug 2010 Posts: 27 Location: Oakland, CA Expertise: I like coffee
Posted Tue Aug 31, 2010, 12:42pm Subject: Re: anyone measure pressure on non-solonoid machine?
I tried to vary the amount of flow and I saw that the pressure does drop a bit as you increase the flow.
I noticed that my older machine seems to have a more powerful pump than the newer machine. I tried moving the same group valve from one machine to another and got slightly different pressure readings - but both gave the same sort of pressure drop with the group valve and full pressure without the group valve.
I also tested by unscrewed the bottom of the group valve a few turns to give a little less tension on the spring. (Still enough threads turned in to hold the valve together) And this brought the pressure up a little - screwing it back in tightly showed the pressure drop again.
Posted Mon Nov 29, 2010, 2:28pm Subject: Re: anyone measure pressure on non-solonoid machine?
gime2much Said:
Following quote from a guy that has done much testing on Gaggias.
"I've done tests using Gaggia machines equipped with adjustable OPVs and 2 gauges: one mounted on the boiler, and the other mounted on a portafilter. My tests show that once the pump is turned on, and the group valve is opened, both gauges displayed the same pressure for the duration of the shot. To me, this proved conclusively that the group valve does not drain off any pressure during the shot."
Anyone else actually tested? I have a Carezza stashed back and a portafilter mounted gauge to test with if needed to prove this one way or another.
This thread really interested me. I have a Carezza with the "spring and mushroom" group valve. I had read many posts where people claimed to use softer springs in the group valve because the group valve was restricting the pressure to the brew head. I have read posts from several people in various forums that have tested and found that the spring loaded, mushroom valve reduces pressure to the brew head.
So I was really curious why the Yahoo Gaggia users group claims the opposite is true - like the quote above which I think is from the Gaggia users group. A Google search turns up plenty of blog postings by people taking the advice of the Gaggia group and installing OPVs on their non-solenoid machines and posting pictures of their project.
This has me really curious about these two contradicting beliefs - they can't both be right - which is correct?
So I set up the test exactly as described in this thread. I mounted a portafilter gauge and removed the spring and mushroom valve from the group valve and I measured 16 bars on the PF gauge. I put the spring and mushroom valve back in and measured 9.5 bars.
I also tried not tightening the valve so the spring wasn't compressed as tightly and got higher pressure at the PF (about 10.5 bars). Then I tightened the valve up, compressing the spring tighter, and the pressure dropped back down again.
The quoted text above, about using an OPV and reading the same pressure at the boiler as at the PF, makes sense for a solenoid valve machine (no restriction at the brew head for a solenoid machine - so it makes sense that the pressure would be the same). But in that quote he seems to be claiming that he is doing this test on a machine with a mushroom valve in the brew head and an OPV installed on the boiler. And based on the results I got, following the test outlined in this thread, I don't believe the above quote is accurate. The only way to get those results would be with the spring removed or by using a very soft spring in the valve. If the spring were very soft, the valve would only act as a check valve to prevent brew water from backing up into the boiler - but wouldn't require any pressure to open and consequently wouldn't work very well when steaming unless you used a blind filter basket.
I tried to ask about this on the Gaggia user's forum - hoping to learn how they got their results and why I got the opposite results. My post was not allowed. I was told that because my test results differed from the list owner's test results it would not be posted and I should NEVER attempt to post anything similar again. PERIOD So much for open discussion and the scientific method.
So that may explain why the Gaggia group seems to be in agreement among themselves - apparently posts with differing views are not allowed.
Posted Mon Nov 29, 2010, 3:02pm Subject: Re: anyone measure pressure on non-solonoid machine?
AndyPanda Said:
So I set up the test exactly as described in this thread. I mounted a portafilter gauge and removed the spring and mushroom valve from the group valve and I measured 16 bars on the PF gauge. I put the spring and mushroom valve back in and measured 9.5 bars.
Thanks very much for re-confirming this. It still puzzles me just a bit, but it's good to know how it actually works and this also confirms for me why the shots from my old Gaggia machine were so smooth when some claimed that the pressure would be too high to produce a nice shot.
AndyPanda Said:
I tried to ask about this on the Gaggia user's forum - hoping to learn how they got their results and why I got the opposite results. My post was not allowed. I was told that because my test results differed from the list owner's test results it would not be posted and I should NEVER attempt to post anything similar again. PERIOD
This thread really interested me. I have a Carezza with the "spring and mushroom" group valve. I had read many posts where people claimed to use softer springs in the group valve because the group valve was restricting the pressure to the brew head. I have read posts from several people in various forums that have tested and found that the spring loaded, mushroom valve reduces pressure to the brew head.
So I was really curious why the Yahoo Gaggia users group claims the opposite is true - like the quote above which I think is from the Gaggia users group. A Google search turns up plenty of blog postings by people taking the advice of the Gaggia group and installing OPVs on their non-solenoid machines and posting pictures of their project.
This has me really curious about these two contradicting beliefs - they can't both be right - which is correct?
So I set up the test exactly as described in this thread. I mounted a portafilter gauge and removed the spring and mushroom valve from the group valve and I measured 16 bars on the PF gauge. I put the spring and mushroom valve back in and measured 9.5 bars.
I also tried not tightening the valve so the spring wasn't compressed as tightly and got higher pressure at the PF (about 10.5 bars). Then I tightened the valve up, compressing the spring tighter, and the pressure dropped back down again.
The quoted text above, about using an OPV and reading the same pressure at the boiler as at the PF, makes sense for a solenoid valve machine (no restriction at the brew head for a solenoid machine - so it makes sense that the pressure would be the same). But in that quote he seems to be claiming that he is doing this test on a machine with a mushroom valve in the brew head and an OPV installed on the boiler. And based on the results I got, following the test outlined in this thread, I don't believe the above quote is accurate. The only way to get those results would be with the spring removed or by using a very soft spring in the valve. If the spring were very soft, the valve would only act as a check valve to prevent brew water from backing up into the boiler - but wouldn't require any pressure to open and consequently wouldn't work very well when steaming unless you used a blind filter basket.
I tried to ask about this on the Gaggia user's forum - hoping to learn how they got their results and why I got the opposite results. My post was not allowed. I was told that because my test results differed from the list owner's test results it would not be posted and I should NEVER attempt to post anything similar again. PERIOD So much for open discussion and the scientific method.
So that may explain why the Gaggia group seems to be in agreement among themselves - apparently posts with differing views are not allowed.
Funny how I am attracted by same topics, in fact I wanted to post before actually reading the thread and realize that this is an old thread still alive..... You are right, the above quote is WRONG, which is worse than not beeing accurate, and it is not a matter of open discussion or contributing personal experience. It is pure maths : if you have 5.5bar spring loaded valve, 15bar E5 Ulka pump and OPV set ,say, at 9.5bar = gage on boiler will read 9.5bar and gage on portafilter will read 4 bar, while if machine was equipped with three way solenoid both gages would read 9.5bar:, and anybody having experience with pressure reducing devices can confirm. Still, if I badly wanted to sell an OPV to a non solenoid machine owner, I would also supply a very soft spring for the mushroom to act ONLY as one way valve, to prove that the two gages read the same..... I would need to make a lot of money on that OPV, in order to justify such a silly operation....... Ciao, Pietro
Well it surprised me - was always friendly before and I figured they would welcome discussion. I must have touched a really hot topic without knowing it.
Bitches_Brew Senior Member Joined: 4 Feb 2009 Posts: 764 Location: indiana Expertise: I like coffee
Espresso: yes Grinder: yes Vac Pot: no Drip: no Roaster: yes
Posted Mon Nov 29, 2010, 4:01pm Subject: Re: anyone measure pressure on non-solonoid machine?
AndyPanda Said:
I tried to ask about this on the Gaggia user's forum - hoping to learn how they got their results and why I got the opposite results. My post was not allowed. I was told that because my test results differed from the list owner's test results it would not be posted and I should NEVER attempt to post anything similar again. PERIOD So much for open discussion and the scientific method.
sounds like a fun place......... heil gaggia users group! ;)
"You can write down how to make the perfect cup of coffee. But to make it really good, you have to play something fictional, you have to dress up, you have to think, This is the most important thing."
JR Senior Member Joined: 31 Mar 2003 Posts: 1,807 Location: Germantown, TN (right next to Elvistown) Expertise: I love coffee
Espresso: Old Coffee Gaggia (x2.5) Grinder: Cunill Tranquilo Drip: the late Melitta Clarity... Roaster: GG/UFO
Posted Mon Nov 29, 2010, 8:56pm Subject: Re: anyone measure pressure on non-solonoid machine?
The Gaggia group is actually quite helpful for most Gaggia owners.
Folks, surely you're aware you only have one side of the story here, since the other party was "banned from CG years ago" (and I have no issue with that, BTW). At least consider that this might not be the WHOLE reason the post was rejected in the Gaggia group.
I don't know both sides, nor do I have an ax to grind. But let's be fair.
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