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The Oscar Saga Continues: Backflush Explosion
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Discussions > Espresso > Machines > The Oscar Saga...  
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GVDub
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Joined: 25 Jan 2008
Posts: 849
Location: Los Angeles, CA
Expertise: I live coffee

Espresso: Londinium I, Arrarex...
Grinder: Gaggia MD85, Dienes Mokka,...
Drip: Behmor Brazen, Abid Clever
Roaster: Behmor 1600
Posted Mon Sep 24, 2012, 6:28pm
Subject: Re: The Oscar Saga Continues: Backflush Explosion
 

As a heat exchanger machine, what comes out of the group is coming directly out of the reservoir tank, not from the boiler.  There are several tutorials around the web on how to descale an HX, but most of them rely on the machine having a hot water tap, There's a YouTube video on descaling an Oscar that should point the way.
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Markarian
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Markarian
Joined: 27 Jun 2012
Posts: 656
Location: Seattle Area
Expertise: I love coffee

Espresso: ECM Technika IV Profi WT-WC
Grinder: Baratza Forte AP, HG One
Vac Pot: Bunn Trifecta MB
Drip: Moka, Aeropress, Hario V60
Roaster: Behmor 1600
Posted Tue Sep 25, 2012, 4:04am
Subject: Re: The Oscar Saga Continues: Backflush Explosion
 

I just descaled the Oscar. Tons of green copper oxide came out and I flushed the boiler out several times until the hosewater smell went away. I also ran descaler through the brew group and got lots of calcium deposits. So I flushed the entire system with at least three or four tanks of water.

Now the machine is useless. No matter what grind setting I'm at--even the one I had finally dialed in for consistently good extraction--each shot comes gushing out in ten seconds or less, blonding at about seven seconds. I have the $600 grinder. I have the (admittedly used) $1000 machine. I spent the entire evening trying to make a working machine work better and now I'm back to square one. I am really starting to get frustrated and discouraged.

To top it all off, the awful rattling noise never went away and I couldn't identify it, even with the cover off.
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GVDub
Senior Member


Joined: 25 Jan 2008
Posts: 849
Location: Los Angeles, CA
Expertise: I live coffee

Espresso: Londinium I, Arrarex...
Grinder: Gaggia MD85, Dienes Mokka,...
Drip: Behmor Brazen, Abid Clever
Roaster: Behmor 1600
Posted Tue Sep 25, 2012, 7:53am
Subject: Re: The Oscar Saga Continues: Backflush Explosion
 

First, don't panic. Almost everything in an Oscar is fixable.

Pull the shower screen and dispersion block and check that the scale coming out of the heat exchanger didn't clog one or two of the ports in the dispersion block. One or two blocked apertures in the dispersion block will drastically increase the pressure coming through the others and cause channeling. Check your puck for signs (like pencil lead sized holes in the top of the puck) of that sort of channeling.
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NobbyR
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NobbyR
Joined: 10 Jul 2011
Posts: 2,023
Location: Germany
Expertise: I love coffee

Espresso: Poccino Opus One, Ariete
Grinder: Eureka Mignon Istantaneo
Vac Pot: N/A
Drip: Melitta Linea Unica de Luxe
Roaster: N/A
Posted Tue Sep 25, 2012, 7:59am
Subject: Re: The Oscar Saga Continues: Backflush Explosion
 

GVDub Said:

First, don't panic ...

Posted September 25, 2012 link

I must get that as a cover for my Kindle. LOL

NobbyR: Don't Panic.jpg
(Click for larger image)

 
***
"This drink of the Satan is so delicious that it would be a shame to leave it to the infidels." (Pope Clement VIII on coffee, when he was urged to ban the beverage)
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GVDub
Senior Member


Joined: 25 Jan 2008
Posts: 849
Location: Los Angeles, CA
Expertise: I live coffee

Espresso: Londinium I, Arrarex...
Grinder: Gaggia MD85, Dienes Mokka,...
Drip: Behmor Brazen, Abid Clever
Roaster: Behmor 1600
Posted Tue Sep 25, 2012, 8:09am
Subject: Re: The Oscar Saga Continues: Backflush Explosion
 

NobbyR Said:

I must get that as a cover for my Kindle. LOL

Posted September 25, 2012 link

Personally, I tend more towards the Bene Gesserit litany from Dune "Fear is the mind-killer. Fear is the little death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past, I will turn the inner eye to see its path. Where the fear has gone, there will be nothing. Only I will remain."

A little bit long for a bumper sticker, though. :-)
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NobbyR
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NobbyR
Joined: 10 Jul 2011
Posts: 2,023
Location: Germany
Expertise: I love coffee

Espresso: Poccino Opus One, Ariete
Grinder: Eureka Mignon Istantaneo
Vac Pot: N/A
Drip: Melitta Linea Unica de Luxe
Roaster: N/A
Posted Tue Sep 25, 2012, 8:24am
Subject: Re: The Oscar Saga Continues: Backflush Explosion
 

"Would it save you a lot of time if I just gave up and went mad now?"
- Douglas Adams, The Hitchhiker's Guide to the Galaxy

That would fit onto a bumper sticker.  ;-)

 
***
"This drink of the Satan is so delicious that it would be a shame to leave it to the infidels." (Pope Clement VIII on coffee, when he was urged to ban the beverage)
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frcn
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frcn
Joined: 23 Dec 2001
Posts: 3,351
Location: Northern California
Expertise: Professional

Espresso: Vibiemme Domobar Double
Grinder: Mazzer Kony, Baratza...
Vac Pot: Hario, 2 Cory pots, 1 Cory...
Drip: Behmor Brazen, Bunn A10 mod...
Roaster: computer controlled Hottop,...
Posted Tue Sep 25, 2012, 9:12am
Subject: Re: The Oscar Saga Continues: Backflush Explosion
 

Markarian Said:

Now the machine is useless. No matter what grind setting I'm at--even the one I had finally dialed in for consistently good extraction--each shot comes gushing out in ten seconds or less, blonding at about seven seconds..

Posted September 25, 2012 link

Sounds like loose scale has clogged the pressure relief valve and so the brew pressure is exceedingly high. Because the Oscar has no pressure gauge, that is difficult to deal with unless you get (or build) a portafilter-mounted gauge.

In hindsight, proper maintenance on a regular basis is highly recommended for everyone. Additionally, knowing the quality of your water helps in creating a maintenance schedule. Using the Aquarium Pharmaceuticals GH+KH test kit. For about $10. Alkalinity and general hardness both have to be present to form scale. This test will measure those two things.  It can also be used to check the effectiveness of your treatment regime, such as deciding when the softener cartridge needs to be replaced or recharged.

 
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Coffeenoobie
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Coffeenoobie
Joined: 11 Dec 2011
Posts: 3,014
Location: PNW
Expertise: I like coffee

Espresso: N S Oscar
Grinder: K30 & Vario W
Posted Tue Sep 25, 2012, 10:34am
Subject: Re: The Oscar Saga Continues: Backflush Explosion
 

I agree with them, don't panic everything can be fixed.  I know it is hard when you are first learning the machine and you have issues like this.  I was there not that long ago.  It probably is a clog of scale that got loose in descaling. This is a risk on any machine when you descale. Kinda like opening up a wall on a 100 year old house.... no telling what you will find.   After rinsing the group and screen and stuff if your pressure is not better then I would start checking the valves.  This issue is why the pros take the machine apart for deep cleaning, the gunk goes in a bucket and not your hoses. Something I plan to do in the next few months.

And when I do, I will document it for everyone to see.  I plan to add the vacuum breaker and maybe a hole in the case and a hose to drain my boiler without removing it.  I don't want to take it apart again till I can do all that work at the same time.

 
Coffeenoobie

Buying advice: GRINDER GRINDER GRINDER. Don't cheap out on the grinder.

My coffee treasure map...
Click Here (maps.google.com)

Oscar trick out: http://s156.photobucket.com/user/GandBteam/story/14231
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Markarian
Senior Member
Markarian
Joined: 27 Jun 2012
Posts: 656
Location: Seattle Area
Expertise: I love coffee

Espresso: ECM Technika IV Profi WT-WC
Grinder: Baratza Forte AP, HG One
Vac Pot: Bunn Trifecta MB
Drip: Moka, Aeropress, Hario V60
Roaster: Behmor 1600
Posted Tue Sep 25, 2012, 1:14pm
Subject: Re: The Oscar Saga Continues: Backflush Explosion
 

I had taken out the diffuser block and shower screen and cleaned them both thoroughly before putting the machine back into commission. I am noticing a LOT of channeling around the sides of the puck. I tried dosing a bit higher (21.5g) and I got a slightly better shot, but I can't get past 20 seconds before it blonds heavily and I have to cut it off. At this point, most of my shots are turning to water within ten seconds. I tried dosing down to 18.5 (since it's supposed to be an 18g basket) and it didn't help. I got channeling in the center. I hate speculating, but it does feel like the brew pressure has changed dramatically, and I can't seem to dial in my grind or technique to compensate for it.

I really appreciate all the encouragement, I really do. But there's a point where I don't have time to mess with this stuff anymore. I'm a full-time student and I also chair a non-profit so that's keeping me pretty busy. During the summer, I got into espresso, but during the schoolyear, I need a machine that just works. I don't want a superauto, and I had gotten comfortable in grinding and tamping my own shots and I was doing fine until I decided to do this big descale last night. Learning how to drive took me months of practice as a teenager but I mastered it and can get from point A to point B, but I still don't expect to tear my engine apart when something goes wrong. I feel like I got sold a lemon and that I'm paying for the sins and neglect of the former owners (who obviously had no idea how to take care of this machine), and I'm starting to lean toward putting this one back on CL and getting a new Oscar that I KNOW will be well-maintained. Either that, or bringing it into NS downtown and telling them "Just make the damn thing work right." Maybe I am missing something obvious, but it's hard to believe that after getting cleaned up this machine would perform far worse than before I decided to give it some love.
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Coffeenoobie
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Coffeenoobie
Joined: 11 Dec 2011
Posts: 3,014
Location: PNW
Expertise: I like coffee

Espresso: N S Oscar
Grinder: K30 & Vario W
Posted Tue Sep 25, 2012, 1:42pm
Subject: Re: The Oscar Saga Continues: Backflush Explosion
 

Once you get past this I believe you will be pleased with your machine. I really don't believe it is a lemon, I believe there is a tiny grain of scale blocking something.  

That is why they recommend pipe sealant goo over pipe tape, because a small thing like a broken off bit of tape can clog up the works.  I really think you can work through this.  Just start at one end and check everything.  Maybe, wait till a day you have time, or the weekend to take it apart. Take lots of photos to help when you put it back together.  I wished you lived closer I would be happy to help you. I have pretty much dismantled mine all the way in the last 10 months.  Oscar is a tank.  It has a blocked something that probably just needs cleaning.  Once you get that fixed you should be fine.  Can you make a video and post so we can hear it?  The main thing is once this thing is humming along it will be very reliable.  Don't get discouraged, you can do this, I did.  I am not a handy guy, or even a guy.

You have it fixed for you, you will not learn anything like you will fixing it yourself.  The costs will be high.

 
Coffeenoobie

Buying advice: GRINDER GRINDER GRINDER. Don't cheap out on the grinder.

My coffee treasure map...
Click Here (maps.google.com)

Oscar trick out: http://s156.photobucket.com/user/GandBteam/story/14231
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