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How should I use the pressure gauges

Posted: Mon Feb 07, 2011 5:23 pm
by richardcoffee
So, I got my new mini - it's making good shots and in just a few days, after reading the CoffeeGeek review on milk and foaming and getting some positive reinforcement from the folks at Chris', I am getting close to making good foamed milk - there's a lot more steam there than I've been used to on my Gaggia Baby Twin. So, now I realize I've got 2 pressure gauges - 1 for the steam boiler and one for the pump. How should I use these? What should I be looking for and when? I see plenty of discussion about pressure on this and other sites - but it seems a little complicated for me. Can you give it to me simply? I'll appreciate it.

Re: How should I use the pressure gauges

Posted: Mon Feb 07, 2011 6:37 pm
by oton
Use the pressure gauge to steam milk? :shock:

I only take a look sometimes to know that the boiler works right and got the normal pressure...

Re: How should I use the pressure gauges

Posted: Mon Feb 07, 2011 8:01 pm
by Endo
You don't use the gauges to make espresso. They are there to make you think you are doing something very complicated (like driving a steam locomotive). :lol:

The designers originally installed only the steam boiler gauge. (That's the way the machines are still shipped from LaSpaziale). Chris Coffee added the dual gauge (Americans love gauges I guess). :lol:

The brew pressure is "set and forget". So a brew gauge is only useful if you are trouble-shooting (or if you plan on entering the next WBC and like to experiment with pressure... in which case you'd buy the portafilter gauge or make one for $10 like I did). On the Mini, all the extra gauge does is flap around from the vibe pump pressure fluctuations (and eventually fail I assume).

The steam boiler gauge is even more useless, since there is no way to adjust the steam pressure ! (They could have easily replaced it with another LED light saying "full steam pressure").

But they are here to stay. I'm sure people would go mental if they were removed. :roll: I guess it adds to the "steam-punk" look we've gotten used to on all espresso machines.

Ohhhh....I forgot..... back to your original question: Steam 1.3 bar, Brew 9 bar.

Re: How should I use the pressure gauges

Posted: Mon Feb 07, 2011 9:59 pm
by richardcoffee
Now that I understand.
Thanks

Re: How should I use the pressure gauges

Posted: Thu Feb 10, 2011 1:22 pm
by jpt
Endo wrote: The designers originally installed only the steam boiler gauge. (That's the way the machines are still shipped from LaSpaziale).
The latter part is not true anymore. I got my Vivaldi from Italy with dual gauges. I've seen several non-US www-pages with the mention of dual manometers.

Re: How should I use the pressure gauges

Posted: Thu Feb 10, 2011 5:38 pm
by Endo
jpt wrote:The latter part is not true anymore. I got my Vivaldi from Italy with dual gauges. I've seen several non-US www-pages with the mention of dual manometers.
Is this the case with the Mini as well? I wouldn't think they would allow it becuase of the vibrating needle.

Does yours say Vivaldi II on the front? Just curious.

Re: How should I use the pressure gauges

Posted: Fri Feb 11, 2011 3:28 am
by jpt
Endo wrote:
jpt wrote:The latter part is not true anymore. I got my Vivaldi from Italy with dual gauges. I've seen several non-US www-pages with the mention of dual manometers.
Is this the case with the Mini as well? I wouldn't think they would allow it becuase of the vibrating needle.
I've seen mentions of dual manometers on Mini adds both on UK and Italy based www-pages. However, I haven't been able to verify it from the pictures (they might be using old pictures?). As I don't own a Mini, I cannot be sure.
Endo wrote:Does yours say Vivaldi II on the front? Just curious.
Yes.

Re: How should I use the pressure gauges

Posted: Fri Feb 11, 2011 9:58 am
by Endo
jpt wrote:
Endo wrote:Does yours say Vivaldi II on the front? Just curious.
Yes.
Interesting. The name Vivaldi 2 used to be an exclusive Chris Coffee thing. I thought they made some kind of agreement they he would be the exclusive seller of the V2 in North America since he worked with LaSpaziale to make the little mods. These mods were never available (or maybe never wanted) in Europe.

I noticed lately that some of these mods have been making there way back into the LaSpaziale Vivaldi V1 sold outside North America. Like my Mini, which has the 1 deg C, new sides, etc. The ony difference on my machine was that it was set by default to 5 deg C (and had the 5 deg C sticker as well). I easily switched it to 1C and swapped the sticker when I got it. It also has the single gauge (which annoyed me at first, but I soon realized was not important).

So if they are now selling what they call the V2 in Europe, then either Chris is now allowed to sell V2's outside North America, or LaSpaziale is now allowed to sell the V2 name. Either way, I guess the original agreement expired.

brew pressure gauge bounces

Posted: Fri Feb 11, 2011 11:40 am
by richardcoffee
So, I finally paid attention to the brew pressure gauge during a shot ---- and, I looked at some older threads here and here's what I found. With my backflush disc in, my brew pressure gauge goes up pretty quickly to 9 bars and stays there till I stop the pump. When making a double or triple shot, the gauge bounces around 7.5. An old thread suggests the bouncing point should be at 9 and so I should increase my pump pressure. But here's what I wonder - before increasing the pump pressure, should I first try a finer grind to increase the back pressure? Isn't the 9 reading with the backflush disc in place and indication that the pressure is set properly? Or, is it really true that this gauge is too unreliable to pay attention to at all? I'm using good fresh coffee with a professional 63mm burr flat grinder. The shots taste pretty good and have plenty of crema.
Thanks for your help.

Re: How should I use the pressure gauges

Posted: Fri Feb 11, 2011 11:45 am
by GDK
Do not touch the pump pressure setting - your machine is calibrated properly to not exceed the 9 bars when choked. What you should play with is grind (try finer) and tamp pressure. Try tamping with 30lb and keep that a constant while playing with grind level. Also pay attention to the extraction time as it may grow in the process beyond what you want.

Re: How should I use the pressure gauges

Posted: Fri Feb 11, 2011 9:07 pm
by Endo
Most people think the gauge measures your pump pressure. Wrong. It measures the resistance to the pump.

Think of it this way, if you put no coffee in the portfilter, it will measure 0 psi (no resistance).

If you put in a blind basket the pressure will go up to the max pump pressure (about 15 psi), but since there is an OPV in place (Over pressure Valve), it will open up and let water out if it goes beyond 9 psi (its max setting usually).

If you put in coffee that has less resistance than 9 psi, it will simply read somewhere between 0 and 9 psi (depending on the coffee resistance factors, like how fine your grind and tamp pressure).

Re: How should I use the pressure gauges

Posted: Fri Feb 11, 2011 11:07 pm
by GDK
Correct, the gauge is properly called "group pressure gauge", as described in the S1 owner manual.

When it comes to rotary pumps (not the case with the Mini), when you have a blind basket to choke the flow, then the gauge indeed measures the max set pump pressure. There is still OPV valve present but it is set at something like 12psi, above the preset pump pressure, for protection only. It is why I suspect some may mix the terminology sometimes. This is where I found the info: http://coffeetime.wikidot.com/rotary-pu ... adjustment. In either case, the gauge should be called group pressure, not pump pressure gauge.

Re: How should I use the pressure gauges

Posted: Sat Feb 12, 2011 5:19 am
by jpt
Endo wrote:Most people think the gauge measures your pump pressure. Wrong. It measures the resistance to the pump.
You are kind of thinking along the right lines, but you are wrong. A pressure gauge measures exactly what the name says; pressure. To be more exact it measures pressure difference. In this case it measures the pressure difference between outside air and the water (at the point where it is attached to the system).

The brew pump moves water from the inlet to the brew system. As there is flow resistance for the water to flow there is also pressure buildup. This flow resistance comes from all the tubing and other things (including coffee) that the water has to go through. If you remove the coffee there is still significant amount of resistance.
Endo wrote:Think of it this way, if you put no coffee in the portfilter, it will measure 0 psi (no resistance).
Have you actually tried this? On my machine the gauge shows about 8 bars without any coffee (after the preinfusion time). During a brew I get a reading of 9 bars. The pressure gauge on S1V2 is attached between the flow meter and the pump. So it doesn't show the grouphead pressure. Is the gauge attached differently on the Mini?

Re: How should I use the pressure gauges

Posted: Sat Feb 12, 2011 7:18 am
by Endo
Just to be clear. I'm only talking about my Mini here (and most othervibe pump machines) since that's what the Richard owns. On the rotary S1, there is a type of OPV built into the rotary vane pump. The external OPV is a fail safe valve, usually set at 15 psi.

And yes. There is some internal resistance (as you point out) so it won't be 0 psi. But in my explanation I'm simply trying to explain why you won't see 9 psi, so I'm exaggerating to make a point. If you want a more details, I'll need to pull out my Moody charts and a calculator. :lol:

Re: How should I use the pressure gauges

Posted: Sat Feb 12, 2011 8:36 am
by jpt
Endo wrote: But in my explanation I'm simply trying to explain why you won't see 9 psi, so I'm exaggerating to make a point. If you want a more details, I'll need to pull out my Moody charts and a calculator. :lol:
Having been a theoretical physicist in the past, I'm always glad to see equations and calculations :lol:, however in this case it is so much easier just to push the button.

Re: How should I use the pressure gauges

Posted: Mon Feb 21, 2011 5:12 pm
by richardcoffee
Interestingly enough, I see now that when I get a good tamp on a triple with the naked portafilter, I get a 9 on the brew pressure gauge - and it corresponds to about a 45 second shot that tastes pretty good.