Markarian Senior Member Joined: 27 Jun 2012 Posts: 474 Location: Seattle Area Expertise: I love coffee
Espresso: Modded Nuova Simonelli Oscar Grinder: Vario-W, Mazzer Super Jolly Drip: Moka, Aeropress, Melitta 102 Roaster: Wear-Ever Popcorn Pumper
Posted Mon Dec 10, 2012, 11:41pm Subject: Re: Oscar Pump Problems (again)
Interesting theory. Can I remove this thing safely when the machine is idling and heated up? Here are the main issues, just stepping back for a moment:
-Brew pressure seems incredibly high, like gushing through each shot, spraying little streamers more than usual and now leaking at the gasket when it wasn't before yesterday (this includes when backflushing). I can pull a 30 second shot, but it's not a very pretty one.
-I NEVER hear the boiler fill click on like I used to. I used to hear it top off at least once every time I would steam more than two lattes. Now I can leave the valve open for a few minutes and it never seems to fill. If I disconnect the probe, I do hear it kick in, so the brain still knows to do it. It's as if the boiler is overfull, but I don't know how to diagnose that, nor why it would be doing it. Nudging the machine sometimes would be enough to get the boiler fill kicking in for a few seconds. Now it doesn't do it.
-There's something else I'm suddenly forgetting
Here's what I have done to try and fix it:
-Adding a diode to the pump, assuming the one inside blew (no change)
-Backed Pstat off by half a turn (Sirai), because I noticed it was WAY too hot as well. Does the boiler temp significantly affect brew pressure?
-Full detergent backflush
-Tightened down fill solenoid housing, which was coming loose
-Adjusted grind, tamp, and roast. Choked the machine, but leaked a lot more around the gasket than it should have.
Here's some additional points to consider:
-Steam comes out strong, but normally with not much excess water, which leads me to believe the boiler isn't overfilled as badly as I thought it was (if at all).
-Pump is brand new, and sounds strong and consistent, especially when backflushing. It was bought new precisely to solve this problem, which seems to have returned.
-NS Tech said there might be some sort of intermittent blockage in the HX, but I have no idea how to test for that or fix it.
I'm kind of lost here, and hoping it's an easy fix to get me back to my 3" crema cones and smooth pulls.
mthedude Senior Member Joined: 28 Jan 2008 Posts: 313 Location: VA Expertise: I live coffee
Espresso: Nuova Simonelli Oscar Grinder: La Spaziale Junior Vac Pot: n/a Drip: Cuisinart Grind & Brew Roaster: n/a
Posted Tue Dec 11, 2012, 1:33pm Subject: Re: Oscar Pump Problems (again)
I'm still thinking the expansion valve is suspect. If you're backflushing and nothing is coming out of that "OPV" and the 3 way doesn't open until you stop brewing, where does all that water go? When I backflush, the basket fills until pressure is high enough to open the "OPV" or expansion valve and water is sent down the red tube. When I stop pumping, the 3 way valve opens and dumps all of the pressurized water into the drip tray.
When you backflush, is any water going into the drip tray while the pump is running?
Markarian Senior Member Joined: 27 Jun 2012 Posts: 474 Location: Seattle Area Expertise: I love coffee
Espresso: Modded Nuova Simonelli Oscar Grinder: Vario-W, Mazzer Super Jolly Drip: Moka, Aeropress, Melitta 102 Roaster: Wear-Ever Popcorn Pumper
Posted Tue Dec 11, 2012, 3:01pm Subject: Re: Oscar Pump Problems (again)
TheDude,
When backflushing, no water comes out the expansion valve tube at all, and water only spurts out of the 3-way valve tube when the brew button is turned off. On the Oscar as I understand it, it's not a real OPV but rather a "Neplax valve" that's designed to open if the pressure exceeds 14-16bar. Some of these valves were adjustable, but some were fixed. There was a big thread of people over on HB adjusting the neplax valves on their Oscars to try and control the unruly brew pressure but did so at the expense of thermal stability because it was on the hot side of the HX. The only way people were able to properly control the brew pressure in that regard was to mod in a real OPV and send a return hose back into the reservoir. When I brew, I do see water moving in the neplax valve tube while brewing, but it seems to be moving TOWARD the group head, not away from it. Either way, I do think you may be on to something and I'll see what happens in the drip tray when I backflush. Can I remove the neplax valve when the machine is on and sitting idle without hurting myself?
Noobie,
Can I just descale the HX by running JoeGlo or KafeKleen through the reservoir and turn on the pump? I don't want to deal with descaling the boiler, and it was fully rinsed and descaled not four months ago anyways.
you COULD(TURN OFF THE MACHINE FIRST). just go really slow and watch out for hot steam. When you unscrew it with the machine hot, the pressure is going to want to release from the opening. Unscrew slowly, let it hiss and let the pressure drop then unscrew the rest of it. Beware, it will be hot.
or, just turn off the machine, wait an hour and do it.
*edit: i added to turn off the machine first because i wonder if the pstat will recognize the drop in temp/pressure and then kick the heater on. Turn the thing off before doing any work.
Coffeenoobie Senior Member Joined: 11 Dec 2011 Posts: 2,317 Location: PNW Expertise: I like coffee
Espresso: N S Oscar Grinder: Vario W
Posted Tue Dec 11, 2012, 4:35pm Subject: Re: Oscar Pump Problems (again)
My understanding is yes, putting it in the tank will run it through the HX but you risk it filling the boiler with it and then you need to flush it out.
Coffeenoobie
Buying advice: GRINDER GRINDER GRINDER. Don't cheap out on the grinder. My coffee treasure map... Click Here (maps.google.com)
Markarian Senior Member Joined: 27 Jun 2012 Posts: 474 Location: Seattle Area Expertise: I love coffee
Espresso: Modded Nuova Simonelli Oscar Grinder: Vario-W, Mazzer Super Jolly Drip: Moka, Aeropress, Melitta 102 Roaster: Wear-Ever Popcorn Pumper
Posted Sat Dec 15, 2012, 7:17pm Subject: Re: Oscar Pump Problems (again)
Okay, so after some testing I think the issue does, in fact, lie with my Neplax valve. I can see water moving slowly in it during brew cycles, and sometimes when I go to flush I can see the water moving quickly and the group sputters and spits hot steam for a few seconds before the water flows, indicating air in the HX. I think this would also explain the inconsistent brew pressure as well.
So I'd like to remove it to inspect it, but it really seems like it's on the group tightly, with a tiny bit of corrosion around the edges where it meets the group. I tried to get it off with a crescent wrench, but it wouldn't budge and I didn't want to force it. Any tips for removing it safely? Frank, I'm worried it will suddenly give and spew hot steam everywhere.
Right now I'm brewing decent shots with good extraction, but I'm not getting that long, flowing cone of crema I was getting before this crap started last week. I want to buy the new 16-bar Neplax I've read about, but NS is closed on the weekends, so I haven't been able to ask about it. It looks like the easiest part in the world to change out if I could just get it unscrewed :(
Posted Sun Dec 16, 2012, 1:11am Subject: Re: Oscar Pump Problems (again)
Markarian Said:
So I'd like to remove it to inspect it, but it really seems like it's on the group tightly, with a tiny bit of corrosion around the edges where it meets the group. I tried to get it off with a crescent wrench, but it wouldn't budge and I didn't want to force it. Any tips for removing it safely? Frank, I'm worried it will suddenly give and spew hot steam everywhere.
Markarian Senior Member Joined: 27 Jun 2012 Posts: 474 Location: Seattle Area Expertise: I love coffee
Espresso: Modded Nuova Simonelli Oscar Grinder: Vario-W, Mazzer Super Jolly Drip: Moka, Aeropress, Melitta 102 Roaster: Wear-Ever Popcorn Pumper
Posted Sun Dec 16, 2012, 5:53am Subject: Re: Oscar Pump Problems (again)
Okay, so got the Neplax valve off. I was able to take it off while the machine was at temperature, but as suggested needed to wait for the steam inside the HX to blow off before I could finish removing it. Once I got it off, I immediately noticed a big, fat piece of scale blocking the socket like a butterfly valve! I removed it and some stray bits of scale here and there.
As for the valve itself, the inside was caked with scale. After a thorough cleaning, inside and out (spring and silicone stopper appear to look fine), I replaced it. I have't tried brewing yet since I need to roast a fresh batch of coffee and I'm still waiting for the machine to heat up, but I did notice that during backflushing I am getting a steady, slow flow through the neplax hose into the drip tray. Is this a good sign?
I also turned my Pstat back up to closer to where it was before all this started. Even with this theoretical valve problem, I have been pulling decent shots with good extraction. The problem is that I'm missing the long, oozing cones I was getting on the pull. Where does the cone come from? Is it brew temp? Pressure? Does it even matter?
Noobie, if this doesn't solve the problem, I'm making another run down to NS this week. Let me know what it was again you wanted. Something for the Musica, IIRC?
Markarian Senior Member Joined: 27 Jun 2012 Posts: 474 Location: Seattle Area Expertise: I love coffee
Espresso: Modded Nuova Simonelli Oscar Grinder: Vario-W, Mazzer Super Jolly Drip: Moka, Aeropress, Melitta 102 Roaster: Wear-Ever Popcorn Pumper
Posted Sun Dec 16, 2012, 8:41am Subject: Re: Oscar Pump Problems (again)
After reinstalling the neplax, I noticed it was leaking during backflushing. I took it out and added more plumber's tape. It was leaking again, so I was worried I might not have tightened it. After trying to get it tighter (it was on there pretty good initially, with a small buildup of scale around it) I stripped the threads on the valve and possibly the group head itself.
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