The idea would be that the by opening the brew valve without starting the pump, the pressure coming from the heating boiler would hopefully be enough to pre-infuse the puck. So we would put a ON/OFF switch between the solenoid and the pump to activate the pump independently from the solenoid.
Our only concern is that we wonder if the water would go back in the entry hose or would it go to the grouphead...
calblacksmith Moderator Joined: 25 Nov 2007 Posts: 7,312 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 Fri Jan 17, 2014, 5:02am Subject: Re: PLEASE HELP ! 3way solenoid pre infusion mod concept (gaggia classic)
Most machines that passively pre infuse use line pressure or around 40 PSI, I don't think you will get enough pressure from the boiler alone. Give i a try though and if you like the results so much the better and if not, you only lost a little time. Oh, BTW, I would not cut holes to mount switches etc until you try it and decide to keep the mod.
In real life, my name is Wayne P. Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!
Feed the newbs, starve the trolls and above all enjoy what you drink!
dwRK Senior Member Joined: 14 Sep 2013 Posts: 78 Location: Houston Expertise: Just starting
Posted Fri Jan 17, 2014, 10:57pm Subject: Re: PLEASE HELP ! 3way solenoid pre infusion mod concept (gaggia classic)
there is an internal stand pipe in the boiler where water goes out to the group...
without the pump...say boiler pressure pushes the water out to the puck...pre-infusion yes...but will have created a steam space between top of the boiler and the pipe...
when you restart the pump...not sure what will happen to this space...will the steam gets push out to the puck...or the pressure collapses the space and you get a shockwave slaming the puck?
it will be an interesting experiment to try...
i would also try the following...same concept with an independent solenoid...activate solenoid/start pump for 4~5s to soak the puck...stop pump for preinfusion...start pump for extraction...stop pump/deactivate solenoid to depressure...
i ended up using a light dimmer mod to the pump...manual pressure profiling including preinfusion :) but I must say I seldom use this doing milk drinks...and only on some beans for espresso...
After reading a tons of topic about the dimer mod, i will choose this one. I will pick a 600w dimer because a lot of people tell the higher is the better to have a perfect control (1bar to 9bar) like this video
DwRK can you take a picture of the internal of your machine and post it, not sure where the dimer is supposed to be wired. Everything I read about this mod was nice, but i never saw the connection..
It would be nice if you can help me with this one ! My machine is a Gaggia classic by the way ;)
Posted Sat Jan 18, 2014, 11:07pm Subject: Re: PLEASE HELP ! 3way solenoid pre infusion mod concept (gaggia classic)
The dimmer is your best option, though I've never tried it. My Classic was plumbed in and it took street pressure to get the puck saturated in about 5 seconds. Ambient pressure from the boiler would not work. Maybe with steam, but you want to avoid that or you'll get channeling.
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