Ceridan Senior Member Joined: 10 Dec 2012 Posts: 31 Location: Prague Expertise: Just starting
Espresso: Rowenta Opio Grinder: Hario Slim
Posted Wed Jan 30, 2013, 8:39am Subject: Gaggia Classic Priming
Hi!
Please would someone explain to me what is the concept of priming and what good it is? I have rather new GC and the manual says it has an "auto-priming" function.
I do it every time before I prepare an espresso, just as the machine manual says thinking it is to clean the head and let the most hot steam/water pour out. But maybe I'm mistaken :)
Priming the machine is to get water into the pipes from the pump to the boiler and to fill the boiler. The auto priming feature on the newer Classics vents air from the pipes leading to the boiler so that the pump can prime, and then closes once pressure builds up in those pipes. This valve is known to fail fairly often and so some users remove it when this happens.
You should only need to prime if the boiler has been emptied or the pipes leading to the boiler vented somehow - either by deliberately draining it, letting the pump run on an empty tank or by steaming until the boiler runs dry. Leaving the boiler heater on (i.e. machine on) on a dry boiler isn't completely fatal to a Gaggia Classic (the element and thermostat is on the outside of the boiler, and is thus designed not to fail with a dry boiler - unlike other machines e.g. Silvia), but you should still avoid running the boiler dry as it will speed up the deposition of scale in the boiler.
After steaming, you should refill the boiler by pressing the brew switch with the steam switch on and the steam valve open - run it until water comes out of the wand, then switch off the pump, switch off the steam switch and close the steam valve to let the machine return to the state where it's ready to brew coffee. This method is also the way to get hot water from the steam wand for making americano.
Cleaning the group head should be done by either running a little water through the group without the portafilter in the place (flushing) between each shot, and by backflushing - running some water into the group with the portafilter in place with either a blind basket or a backflushing disk (something that sits in the basket to block the flow through the basket). You can backflush fairly often with plain water - say after every session of pulling drinks, or weekly if you only pull one drink in a session, and use an (aluminum safe) espresso cleaner in basket for backflushing every month or so (dependent on amount of use).
the manual says it has an "auto-priming" function.
I do it every time before I prepare an espresso, just as the machine manual says thinking it is to clean the head and let the most hot steam/water pour out.
Sorry to ask for clarification/verification of the self priming valve, but could you take the top off of the machine and look for the steam valve assembly and confirm the self priming valve. I have not heard of this in the Classic, and show it here for you to verify. It should look like part 12 and tube 11 on this "Deluxe" diagram.
I am trying to confirm that they have really changed. Before long, you will likely want to put a plug in place of the priming valve as they develop leaks.
If you prime "every time before I prepare an espresso" do you mean just before brewing the espresso, or as you are warming the machine? Are you manually priming with a self prime valve? Are you opening the steam valve and turning on the pump with the brew switch? No need to hit the steam switch unless you do not want water out the group. I prime after steaming by leaving the wand open, turning off the steam switch and thus not further heating, and turning on the pump. Water will go out the wand until the boiler is full and then come out the wand and group.
If you do any priming shortly before the brew, how are you maintaining temperature? The boiler is small and you would be putting in cold water and dropping the temperature. You can learn to surf the temperature by causing the heater to turn back on this way, if that is what you are trying.
What I usually do is that I switch the machine on, wait for 15-20 minutes, flush some water into a cup (and thus heating it, later I empty it) and put the portafilter in (to heat it). Then I grind coffee in my hand grinder, take out the portafilter, put the basket in, fill the basket, tamp it, put it all on asna start brewing coffee.
Good or bad? :)
@D4F There is nothing on my Classic as you describe.
Btw, can I unplug the wire used to heat up the place used to heat cups? (I know, very cumbersome description.)
Umm, there isn't a specific cup warmer heater in the Classic - the heat from the boiler does that. So there's no wire that can be removed.
Your procedure sounds right, although I'd put the PF in at the start to get it properly up to temperature. I'm not sure what the question about priming is now though.
Sorry to ask for clarification/verification of the self priming valve, but could you take the top off of the machine and look for the steam valve assembly and confirm the self priming valve. I have not heard of this in the Classic, and show it here for you to verify. It should look like part 12 and tube 11 on this "Deluxe" diagram.
The Classic has no self-prime valve... only the lower-end Coffee. I have plugged it on mine as it started to slowly bubble when the machine was at temp. The problem is that it uses a rubber ball to seat and seal the "valve" and heat bakes the rubber until it is no longer soft enough to seal. Extremely cheap short-lifespan design, and unnecessary to boot.
Ceridan, thanks for clarifying that the auto-prime in the manual does not mean self prime. I was fairly sure of that unless they changed the feature on your new machine, the reason to clarify that for the thread. Now you have gotten to look inside familiarize yourself somewhat :)
Your priming and warm up procedure seem fine, though as mentioned, the PF and basket can be kept on the machine while warming, and removed only for loading the ground coffee.
I believe your extra wire may be a ground wire. You are in Prague and I am not sure of wiring there, but some Classics have had 3 wires input, one being a ground wire. If so, there was a ground to the lid/warmer. In the above Classic diagram, part 4, the metal portion of the lid has a bent down leg at the back where it attaches to the plastic portion. The down leg is for a ground wire in 3 wire systems. In the US, we have 2 wire and that leg is not used. So, do not unplug.
OK, thanks. We have wires with groundind here, so I will not unplug the wire :) So far I plan to adjust the pressure to ~9 bars, but I don't have the right tools at the moment.
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