dman777 Senior Member Joined: 26 Dec 2011 Posts: 236 Location: austin Expertise: I like coffee
Espresso: Silvia- No PID Grinder: Compak k3 touch Drip: french press
Posted Wed Jan 11, 2012, 7:18am Subject: Opinions about this Gauge kit for the Silvia?
It sux that the Silvia's come out of the factory at 11 bar pressure for their epod kits. I would like it to be 9 bar pressure, so I might as well do the gauge mod.
1) The gauge seems good quality. It states it is oil filled so virbations will not influence it. Any opinions on this? 2) Is the copper wire safe for my food and water? I know copper is best for the heat going through, so not sure if the trade off is good enough. 3) Looks like a pretty simple install.
calblacksmith Moderator Joined: 25 Nov 2007 Posts: 5,642 Location: Riverside, Ca, U.S.A. Expertise: I live coffee
Espresso: ECM Veneziano A1 Grinder: Many different commercial Vac Pot: 40s era Silex Drip: Milita, Bunn&Curtis... Roaster: Cast iron pan, gas burner
Posted Wed Jan 11, 2012, 8:01am Subject: Re: Opinions about this Gauge kit for the Silvia?
Copper will not hurt your coffee or machine. Oil filled gauges are better at displaying information when the pressure is not steady, IE a vibe pump, the oil tends to dampen the pulses. I don't know anything about the seller or the quality of the kit. You can tap into the brew system anyplace but if you tap into it before the OPV (like in this kit) you will read the pressure of the pump, not what is going into the brew head.
To read the brew pressure, you would need to put a T in between the boiler and the OPV, which is screwed directly to the boiler which is attached to the brew group.
Short of adding in this T, you can move the location of the OPV like I did in my rebuild of Silvia or you could use a gauge that mounts to your Porta Filter but locating the gauge at the pump only shows the pump pressure, this is not what you are wanting to see when trying to adjust the brew pressure. Link to my Silvia thread. http://coffeegeek.com/forums/espresso/machinemods/547829
In real life, my name is Wayne P.
Feed the newbs, starve the trolls and above all enjoy what you drink!
Posted Thu Jan 12, 2012, 8:36am Subject: Re: Opinions about this Gauge kit for the Silvia?
I've been thinking about this after doing some pressure testing on a few of my machines. But I did not have an inline gauge installed - just a portafilter gauge - so I couldn't test during an actual pull - only a simulated one.
For a machine like the Silvia (or the Gaggia Classic) where you have an OPV and a 3-way solenoid, it seems to me, that with the OPV valve set to 9 bars then as long as the puck has enough resistance that you see water returning to the reservoir (from the OPV) while pulling a shot then you will be seeing exactly 9 bars at the coffee puck (or whatever pressure the OPV is set to).
I mean ... if the coffee puck ever saw less than 9 bars of pressure then the OPV would not be bleeding anything off. So I would expect that if the coffee were ground coarse enough (or packed loosely enough) that your pull was a gusher - then you might not see 9 bars - and if that were the case you also shouldn't see/hear any water being bled off by the OPV. But I would expect anything between a perfect grind/dose/tamp and a total lockup would have the OPV bleeding off water and you would see exactly 9 bars on your gauge (or whatever pressure the OPV is adjusted to).
Calblacksmith ... (or anyone else who has a pressure gauge installed), Is this what you see? Or does the pressure change during the pull depending on the grind/tamp -- or does it stay at the pressure you have the OPV regulated to?
calblacksmith Moderator Joined: 25 Nov 2007 Posts: 5,642 Location: Riverside, Ca, U.S.A. Expertise: I live coffee
Espresso: ECM Veneziano A1 Grinder: Many different commercial Vac Pot: 40s era Silex Drip: Milita, Bunn&Curtis... Roaster: Cast iron pan, gas burner
Posted Thu Jan 12, 2012, 12:27pm Subject: Re: Opinions about this Gauge kit for the Silvia?
it really depends on the design of the machine, if opv valve is before the boiler then the most you could ever see in the system would be 9 bars, and anything over that from the pump would be diverted back tp the tank regardless of hpw much resistance os offered by the coffee. If the opv valve is located at the boiler like on the sylvia then if the coffee offers more resistance then 9 bars, you will see the excess pressure diverted back to your tank.
however with either system you will still be supplying up to 9 bars of pressure to the coffee depending on how the coffee was ground and how much resistance it is offering to the water and you would need to grind your coffee to achieve the 25 approximate seconds for your pull to complete.
In real life, my name is Wayne P.
Feed the newbs, starve the trolls and above all enjoy what you drink!
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