benpiff Senior Member Joined: 5 Feb 2010 Posts: 277 Location: Portland, OR Expertise: I live coffee
Espresso: Rocket R58,Brewtus... Grinder: Vario Roaster: Sonofresco 1lb, Behmor
Posted Sun Apr 7, 2013, 10:12pm Subject: Grimac La Uno low brew pressure, first plumbed in machine
I didn't get to test this machine before I bought it, but when I first got it T'd into my sink's cold water line and turned it on, I was able to get water out of the group and everything heats normally. But before pulling a shot, I used my portafilter gauge with needle valve to check brew pressure. The pressure seems to build very slowly, not get above maybe 2-3 bar, and make the machine get very noisy.
The first thing I experimented with was adjusting the OPV tighter, which made the pump louder, the pressure go up a bit (but never past maybe 3 bar), and noticeably less water come through the 3 way valve.
What else should I check? There is a rubber line that runs to the drip tray from another junction box and never see water flow into it (this person has a good photo of it Click Here (s756.photobucket.com)), do you know if this is an expansion valve for the heat exchanger, or is this an OPV (the OPV after the pump just loops back into the line before the pump)? Is my water line pressure the next culprit? I know calibrating the two pressures could be a unique setup for me, so if anyone can email me directly to explain the process for this machine, you'd be a hero!
Edit: I've read a couple different threads that showed people opening up the expansion/OPV valve, and also discussing scale buildup. I definitely have been more distracted by the plumbing aspect than possible scale, so I took out the of the E61 to check the mushroom and gicleur, both looked really good. I removed the expansion valve and there was some murky water in there, but running the pump for a second cleaned that up. I can't get any water to flow through the expansion valve whether it's loose or tight, and adjusting the OPV by the pump still doesn't result in the pressure getting beyond 4 bar in 30 seconds. How long should it take to fill a 2oz shot glass around 9 bar of brew pressure?
Edit 2: I've now done a Cafiza backflush, fully descaled the machine, opened and checked the OPV. It still takes about 25 seconds to fill my 2oz shotglass. Is it most likely the pump or the path to the group?
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