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Oscar PSTAT adjustment needed?
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Discussions > Espresso > Machines > Oscar PSTAT...  
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Markarian
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Markarian
Joined: 27 Jun 2012
Posts: 658
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 Sat Jan 26, 2013, 3:21pm
Subject: Oscar PSTAT adjustment needed?
 

Okay, my brain isn't built for logic today so forgive a possibly obvious question.

My Oscar stays on 24/7 and has been working fine lately. It has a very predictable flush, steam pressure, etc. This morning I noticed the hissing coming out of the group was much shorter than usual. When I brewed, there was hardly any ramp-up of pressure behind the puck as there usually is and the coffee just started coming right out much earlier. It wasn't a particularly bad shot, but it wasn't as good as usual either. Throughout my session of making one latte, the autofill kicked in no less than three times, when usually it barely kicks on once during making two lattes. So my question is, does the Pstat need adjusting and does the pressure need to come up or down? Thanks!
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germantownrob
Senior Member
germantownrob
Joined: 2 Dec 2007
Posts: 2,153
Location: Philadelphia
Expertise: I love coffee

Espresso: Duetto 3, A Dead Oscar
Grinder: Vario-W, Preciso w/Esatto,...
Drip: Brazen
Roaster: Diedrich IR-1, HT B
Posted Sat Jan 26, 2013, 5:07pm
Subject: Re: Oscar PSTAT adjustment needed?
 

So turning your Pstat up will create more pressure in the boiler and raise the temperature in the boiler which will increase the temp of your group which will require a longer flush. I would normally need two Pstat adjustments in between de scales to maintain the same flush.

The boiler pressure in an HX system has nothing to do with brew pressure, it does effect steam pressure. The pump is what creates your brew pressure and a channeled shot can explain what happened on your one shot it is not enough to worry about IMO.

Through the 3.5 years of my Oscar I found using 6-7 gpm water I needed to descale every 6-8 months to avoid a 3rd Pstat adjustment, I never felt my machine was ever in desperate need of descale at 6-8 months and probably could have gone a full year with 1-2 more adjustments.
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Markarian
Senior Member
Markarian
Joined: 27 Jun 2012
Posts: 658
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 Sat Jan 26, 2013, 5:17pm
Subject: Re: Oscar PSTAT adjustment needed?
 

Thanks, Rob. The machine was completely descaled, with the boiler actually opened and hosed out afterward about four or five months ago. Since then, I've ben using Pur-filtered water exclusively for filling the tank and haven't noticed any odors or blockages, etc. I do a detergent backflush about once a month, and a regular backflush every day.

Someone said on here, I seem to recall, that if there's ANY hissing steam when you first run the brew head, then the temperature is hot enough, and it just depends on how long you flush after that which determines your brew temp. Like I said, my machine just seemed a little...off today and it's hard to explain. I don't know if there's been a reduction in steam pressure or not, to tell the truth. Would the machine refilling itself more frequently indicate that the pressure is too low?
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germantownrob
Senior Member
germantownrob
Joined: 2 Dec 2007
Posts: 2,153
Location: Philadelphia
Expertise: I love coffee

Espresso: Duetto 3, A Dead Oscar
Grinder: Vario-W, Preciso w/Esatto,...
Drip: Brazen
Roaster: Diedrich IR-1, HT B
Posted Sat Jan 26, 2013, 10:04pm
Subject: Re: Oscar PSTAT adjustment needed?
 

Refilling often means water has left and needs replacing, other then steaming the boiler has no other loss unless there is a leak, so if it filling more and your steaming routine is the same look for leaks.

Pur water is filtered water, it does not change the hardness of water.  If water is below 3gpm it will not make a scale problem, over that and the scale will need to be delt with. Zero water is a system that does reduce hardness, from what I gather it gets expensive over time with filter replacements. I sprung a leak with my last descale of Oscar and now I am done with descale, water softening her I come.

Edit: it dawned on me that there was a time I thought the boiler was all that needed descaling, the HX system is where scale built up that 1.5 years while the boiler was darn clean. My boiler was spic and span but all the HX tubing and pump where slowing down with scale, that was fun to clean. After that I knew what I was doing.

I created a leak in my Oscar because I knew exactly how to descale from many years and times of practice. I overfilled my boiler to get the solution up to the place where  scale is, above the waterline , and left it to heat up. I forgot to turn it off, normally the safety release on the boiler would blow, it didn't and with pressure and the aid of citric acid a new release was made.
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Markarian
Senior Member
Markarian
Joined: 27 Jun 2012
Posts: 658
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 Sun Jan 27, 2013, 2:05am
Subject: Re: Oscar PSTAT adjustment needed?
 

Damn, that's rough :(

In my case, I'm noticing that after being left for a few hours, the water doesn't immediately come out of the group when flushing. Instead, there's a hissing and one or two seconds later, steamy water comes out. Also, I sometimes don't get a smooth flow, with the flow stopping for a split second before resuming. Not sure what to make of it. I opened the machine and spotted no leaks, or heard anything unusual.
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Markarian
Senior Member
Markarian
Joined: 27 Jun 2012
Posts: 658
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 Sun Jan 27, 2013, 6:02am
Subject: Re: Oscar PSTAT adjustment needed?
 

Here's a video I took of a flush. Check out 0:19

http://dl.dropbox.com/u/2433619/OscarPump1.MOV

While we're at it, does my pump sound normal?

Also, what do you think, Helen? Thanks again, everyone!
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germantownrob
Senior Member
germantownrob
Joined: 2 Dec 2007
Posts: 2,153
Location: Philadelphia
Expertise: I love coffee

Espresso: Duetto 3, A Dead Oscar
Grinder: Vario-W, Preciso w/Esatto,...
Drip: Brazen
Roaster: Diedrich IR-1, HT B
Posted Sun Jan 27, 2013, 7:49am
Subject: Re: Oscar PSTAT adjustment needed?
 

Markarian Said:

Here's a video I took of a flush. Check out 0:19

http://dl.dropbox.com/u/2433619/OscarPump1.MOV

While we're at it, does my pump sound normal?

Also, what do you think, Helen? Thanks again, everyone!

Posted January 27, 2013 link

Interesting, the pump sounds normal to me but Helen is the Oscar whisperer. How much volume of water are you getting? I couldn't tell if flow was restricted.
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Coffeenoobie
Senior Member
Coffeenoobie
Joined: 11 Dec 2011
Posts: 3,036
Location: PNW
Expertise: I like coffee

Espresso: N S Oscar
Grinder: K30 & Vario W
Posted Sun Jan 27, 2013, 12:47pm
Subject: Re: Oscar PSTAT adjustment needed?
 

That is really strange. The pump was a bit loud and did not get quiet when the flow stopped.  The flow stopping looks bad to me.  Makes me wonder if you don't have a slow leak in your HX in the boiler.  But then you said the boiler seemed low to you and filling more.  Open the drip tray and do it again and see if water is coming out down there when the water pulses.  

Also, when my safety valve went out it caused pulsing and steaming at the group head.  It could be the beginning of that.

 
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: 658
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 Sun Jan 27, 2013, 2:18pm
Subject: Re: Oscar PSTAT adjustment needed?
 

I've been watching the neplax like a hawk and its been bone dry since I installed it, thankfully. The machine HAS done this before, and I can't remember what I did--if anything--to resolve it. Before I replaced it, I do know the neplax was opening during brewing and backflushing and eventually causing there to be an excessive amount of air in the HX, but this seems a lot more subtle than that. I'm really curious if the 3-way valve could have anything to do with this too? I have the sneaking suspicion it doesn't open as often as it should (though does during backflushing). Could this also have to do with the valve that directs flow between the boiler and brewing?

I'm going to go try to pull a shot and remove the tray like you suggested, Helen. I'll run the water by itself and see if anything happens when there's pulsing.
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Coffeenoobie
Senior Member
Coffeenoobie
Joined: 11 Dec 2011
Posts: 3,036
Location: PNW
Expertise: I like coffee

Espresso: N S Oscar
Grinder: K30 & Vario W
Posted Sun Jan 27, 2013, 2:23pm
Subject: Re: Oscar PSTAT adjustment needed?
 

I am thinking just run water and when it pulses look at the tray and see if there is any water coming out during the no water at the top time. If the 3 way is doing something you should see water coming out the bottom on the other side- I would think.

 
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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