group pressure

Did you have a bad "out-of-box" experience with your Mini? Describe it here and report back with the final resolution.
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wru
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group pressure

Post by wru » Sun Dec 25, 2011 3:19 pm

hi all, message into Chris but impatience getting the best of me with the new toy... pump primed and getting continuous flow without any restriction in place (espresso, backflush disc, etc). will not push a shot, pressure builds to 4-5 bar then opv blows. same with espresso and backflush disc; pressure never climbs above 4-5 bar before opv blows.

where to start?

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chas
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Re: group pressure

Post by chas » Sun Dec 25, 2011 4:44 pm

Can you explain what you mean by "OPV Blows" in more detail? The VII "Maxi" does have such a valve that opens into the drip ray if the pressure exceeds 12 bar (unless of course it is not properly set). However, the same device on the Mini does not drain into the drip tray. Rather there is a clear plastic tube that routes the flow back to the input of the pump when the pressure exceeds 9 bar. So in the Mini this device is actually what sets the output pressure to 9 bar. There is no sense of it "blowing".

Since this should have been set to 9bar by CCS before shipping it to you and there is a very strong spring inside, it is hard to believe it could have vibrated enough in transit to get that far off. However, even if it is set to 4-5bar, there is still nothing to blow in this case, the group pressure would just be low.
Chas
LM GS/3 & LaSpaziale Dream v 1.23 (US 120V)
Mazzer Kony E, Customized Rocky
Hottop P/B

wru
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Re: group pressure

Post by wru » Sun Dec 25, 2011 6:04 pm

ok, then i'm totally confused. thanks for the quick response, let me walk through what i'm doing;

primed pump and have steady flow.
set temp to 93
set dose for single and double 1oz and 2oz respectively
heat portafilter with a double run through
grind, dose, tamp

lock portafilter, confirm temp at 93 and hit the double button - at this point, the group pressure gauge is reading 1-2 bar. pressure rises to 4-5 bar, then i get full pressure drop and a strong burst of liquid back into the drip tray from below (right side, rear). i assumed this was OPV. I'm coming from a silvia and would get that if grind was too fine and the silvia would choke.

by the way, i did have the progressive p/i installed by Chris' coffee, if that matters. haven't taken anything apart yet, but i guess that's next... let me know thoughts, please!

thanks in advance.

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chas
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Re: group pressure

Post by chas » Sun Dec 25, 2011 6:19 pm

That sounds like the programmable volumetric flow is set to such a low value that it stops and dumps out the 3-way valve before the group pressure even gets to 9bar. To get started, assume that you need about 3 ounces of water through the group with no coffee in the PF since about an ounce or a little more soaks into the coffee. Just follow the instructions in the manual to set the flow to about 3 ounces for both the 1 cup and 2 cup buttons. Once you get both buttons programmed for enough flow to not have this problem any longer, you can fine tune the flow later.

I think you're going to luck out on this one. Before you even try the above, you might try the 1 cup button since you say you are seeing this on the two cup button to see if the same thing happens with the 1 cup button. It's possible that only one of them is set wrong.
Chas
LM GS/3 & LaSpaziale Dream v 1.23 (US 120V)
Mazzer Kony E, Customized Rocky
Hottop P/B

wru
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Re: group pressure

Post by wru » Sun Dec 25, 2011 6:24 pm

ok, let me check it and back shortly - really appreciate your patience and quick responses!

wru
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Re: group pressure

Post by wru » Sun Dec 25, 2011 6:52 pm

user error... fixed! turns out that puck holds quite a bit - i had to put over 4 oz. through it to get a full double. my mistake was in setting the volumetric without coffee in the portafilter.
thanks again for your quick help and have a great holiday!

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