HAL9000 Senior Member Joined: 11 Jan 2004 Posts: 294 Location: Connecticut
Posted Tue Dec 28, 2004, 1:55pm Subject: Re: NS Oscar Questions (repost from wrong forum)
I am finding the Oscar cannot push through a tripple, is that normal?
Andy,
Funny you should say that. I just started using a triple and have had to coarsen up my grind considerably. Also, this seems to have caused a new pump noise, which I have not been able to clear in the way I explained. It is unnerving.
I have heard others suggest using the triple in this machine, so I wonder if the problem is a matter of making adjustments.
Have you tried to adjust your temperature? I learned this weekend that mine was very low, and some research turns up that this is common with Oscars due to NS's factory settings and questionable opinion of what is the right temperature. Boosting the temperature made a huge difference in shot quality.
hifi_guy Senior Member Joined: 4 Apr 2004 Posts: 266 Location: Germany Expertise: I love coffee
Espresso: Simonelli Oscar & Personal V Grinder: Simonelli MDE, Ranc.MD50,... Vac Pot: none Drip: Melitta Cone, now unused
Posted Wed Dec 29, 2004, 5:16am Subject: Re: NS Oscar Questions (repost from wrong forum)
Hi, my PF pressure gauge arrived yesterday. Since you asked, Paul...do get one! It takes the guesswork out of one important parameter, so you can concentrate better on the countless others that remain unknown;-)
As described in an earlier thread, I had already adjusted the pressure limiting valve based on an approximation of the volume of drained water when running against a blind filter. This method was complicated by the fact that my Oscar seems to have an uncommonly strong pump that has a water debit higher than the values published on all Ulka pumps. So I didn't have the pressure/volume curve for "my" pump and had to make a guess. Anyway, the results weren't that bad: Measured now with the gauge, it had been running at 10 bar. I dropped it to 9 yesterday. If you're making ristretto-ish shots now, you can sometimes hear the valve opening after the initial pressure ramp-up. You didn't need a gauge to see that the factory setting on my machine was too high, though: Originally the adjustment nut was simply closed all the way and the valve wouldn't even open with a blind filter. Strange. I wonder how yours is set.
I also played around with temperature/pressurestat settings, and am continuing to do so. Had to stop yesterday night after I nearly ran out of coffee (had to save two doubles for breakfast). By that time I was close to a heart attack anyway.
Got a fresh pound o'beans now. And with the gauge, I also received new burrs for the old Rancilio MD50 monster grinder that's lying on the workbench disassembled. So where should I start?
Ciordia9 Senior Member Joined: 22 Oct 2004 Posts: 103 Location: Charlotte, NC Expertise: I live coffee
Espresso: Nuova Simonelli Oscar Grinder: Eureka MDE Grinder Vac Pot: Bodum Santos Drip: French Press Roaster: Heat Gun!
Posted Wed Dec 29, 2004, 11:38am Subject: Re: NS Oscar Questions (repost from wrong forum)
HAL9000 Said:
Andy,
Funny you should say that. I just started using a triple and have had to coarsen up my grind considerably. Also, this seems to have caused a new pump noise, which I have not been able to clear in the way I explained. It is unnerving.
Ah you too eh? :) I have to go way coarse for it to pull anything, and once it decides to flow its too fast.. and its waay off my normal grind so something has to change for it to work for me.
I have heard others suggest using the triple in this machine, so I wonder if the problem is a matter of making adjustments.
Have you tried to adjust your temperature? I learned this weekend that mine was very low, and some research turns up that this is common with Oscars due to NS's factory settings and questionable opinion of what is the right temperature. Boosting the temperature made a huge difference in shot quality.
What were you using to test temperature? I'll gladly dial up some better settings with a little gear. I never got the pressure gauge, what version are people picking up for our unit? a PF modification?
I feel on a great day I pull things that are beauty unmatched, but for the most part lately my ratio has been a bit off. Through this process though I am learning a wonderful amount of details that will most certainly be of use in the future.
-a
http://andy.ciordia.info "Life is all about strategy, mathematics and psychological perceptiveness."
HAL9000 Senior Member Joined: 11 Jan 2004 Posts: 294 Location: Connecticut
Posted Wed Dec 29, 2004, 12:42pm Subject: Re: NS Oscar Questions (repost from wrong forum)
Bernhard,
My pressure valve was in the same state as yours. I am convinced to get a gauge. Could you tell me what a "water debit" is, and where I might find the Ulka info?
You should check your life insurance policy to make sure it covers in the case of death by espresso. The coroner WILL find the crema residue, you know...
Andy,
I am using a $20 or $30 Craftsman (sears) multimeter that came with a thermocouple. I shove the thermocouple tip under the insulation in contact with the boiler skin. For good measure I put a blob of axle grease that is rated to 350F on the tip before pushing it into place. Works very well. This has told me that the boiler temperature range (with the old-style pstat) is approx. 12 degrees and sometimes as much as 14!
I have also tried using the thermocouple in the puck by drilling a small hole in a rarely used filter basket and inserting the thermocouple before adding the coffee. Am not happy with these results yet but will keep trying. And I think that axle grease may be imparting some off flavors. Just kidding - no grease in the basket.
You mention your shots are off lately. It is funny, the more I learn the worse my coffee gets! But I do expect it will be better in the end.
hifi_guy Senior Member Joined: 4 Apr 2004 Posts: 266 Location: Germany Expertise: I love coffee
Espresso: Simonelli Oscar & Personal V Grinder: Simonelli MDE, Ranc.MD50,... Vac Pot: none Drip: Melitta Cone, now unused
Posted Wed Dec 29, 2004, 4:13pm Subject: Re: NS Oscar Questions (repost from wrong forum)
The coroner WILL find the crema residue, you know...
LOL... I dont think he will find much in the way of crema. It dissipates much too quickly. Used to be better, I swear...
It is funny, the more I learn the worse my coffee gets!
same here, absolutely. and now even my crema disappears...
Could you tell me what a "water debit" is, and where I might find the Ulka info
I had the info (and the whole idea for the gauge-less adjustment technique) from another_jim's post "Adjusting vibe pump pressure on HX machines". You may have seen it. The pressure vs. volume curves can be found here. Ulka has a bunch of different models for espresso use, so ideally, you know what pump you have exactly. There's a link to the "performance curve" for each pump model. About that "water debit"...uhmm...the term sounded strange to me, too. I've encountered it several times in posts on CG (not the quoted one, though) to describe the water output of a machine against atmospheric pressure i.e. with no PF attached. In the Ulka tables, this is found as "Max. Flow Rate (cc/min)"; the dimension cc/min is identical to ml/min. This is easy to measure with just a watch and a calibrated container or a kitchen scale. Usually you seem to get around 600ml per minute. But I got over 1000ml/min. No wonder this pump is LOUD. But I'm not sure if this has any real significance. My Oscar has always been noisy, by the way. But when it runs out of water, I get noisy, too. Especially when it dies right in the middle of a shot and/or refuses to return to work after refilling. Adjusting the pump pressure down to 9 bar may have been good for my peace of mind, but didn't significantly improve my shots. Well, maybe it did, a bit. But I'm still fighting bitterness and lack of sweetness and body. Interestingly, the better shots have suspicious amounts of grounds at the bottom of the cup. I'm not sure how much is acceptable but I would like to see less. Tomorrow I'll try to get my MD50 up and running, if only to rule out the (admittedly remote) possibility that the MDE is causing the problem.
HAL9000 Senior Member Joined: 11 Jan 2004 Posts: 294 Location: Connecticut
Posted Wed Dec 29, 2004, 4:40pm Subject: Re: NS Oscar Questions (repost from wrong forum)
Bernhard, thank you for all of that information. I have some reading to do...
I actually had read part of that "how to adjust" thread, and made the same adjustment you did to the OPV. When I was getting approx. 2.25 oz. in 25 seconds I figured I was in fat city.
But that adjustment completely destroyed my crema. A little knowledge in the wrong hands...
So I cranked it back up most of the way and my crema returned. Now I am really looking forward to setting up a gauge to find out what the heck is going on.
For what it is worth, I adjusted the pstat to the point just below where it causes the safety valve to hiss (as Jack Denver has recommended on alt.coffee) and that raised my boiler skin high/low temps to 240-252F or so. Before making this adjustment the temp was generally in the 230s. Not sure yet what the brew temp range is, but this did result in a big improvement in flavor.
By the way, do you see any bubbling in the hose that drains the OPV into the drip pan during a shot? I do, but think I should not.
hifi_guy Senior Member Joined: 4 Apr 2004 Posts: 266 Location: Germany Expertise: I love coffee
Espresso: Simonelli Oscar & Personal V Grinder: Simonelli MDE, Ranc.MD50,... Vac Pot: none Drip: Melitta Cone, now unused
Posted Thu Dec 30, 2004, 4:32am Subject: Re: NS Oscar Questions (repost from wrong forum)
Hi,
lowering the pressure does affect the crema. I wonder how the big commercial machines that make wonderful, smooth shots and loads of crema are set. But with Oscar I get the feeling I have to decide for one or the other. Cranking the pressurestat all the way up seems a strange measure to take. Normally you would expect this to lead to burnt, bitter tasting espresso. But in combination with a pressure-adjusted Oscar, I have a different theory: As you and I experienced, the units seem to come from the factory with the overpressure valve practically deactivated. So every single drop of water that is pumped through the HX ends up in the coffee. With the OPV set to a lower value, such as 9 bar, you split the water stream: You have your espresso (now guaranteed to be extracted at the correct pressure) and an additional volume of water that's drained to the drip tray. Especially with a strong pump like the one in my Oscar, this may lead to an increased total flow rate. Problem is, the valve is downstream of the HX, not upstream as in many other machines. So the increase in flow goes through the HX. I guess every heat exchanger has its limit. Maybe this is reached with an Oscar when you open the OPV too far, and the temperature drops dramatically during the shot. So you pay for the correct pressure – with an instable temp profile. Increasing pstat setting may reduce the temperature drop, but will increase overheating during idle and make the whole system even more critical.
That's only theory, and I have no means to check it. Anybody know how critical the HX reacts to increased flow?
Paul, do you use a cooling flush? How big? I cannot see any bubbling in the hose that connects the OPV to the drip tray. But then, that hose is made of red, non-transparent rubber in my Oscar. So I don't see anything;-)
About the variance in boiler skin temp: this is defined by the deadband of your pressurestat (the pressure difference between "on" and "off" condition). The deadband seems to increase with pressurestat age, ultimately leading to the pressurestat having to be exchanged/repaired. I don't know how old yours is, and how long it has been running. But maybe the variation in Boiler temp could be lowered with a new pstat? Cheers,
HAL9000 Senior Member Joined: 11 Jan 2004 Posts: 294 Location: Connecticut
Posted Thu Dec 30, 2004, 3:52pm Subject: Re: NS Oscar Questions (repost from wrong forum)
Interesting thought on the placement of the OPV. I agree with your idea, and wonder why it is located where it is. I called NS the other day and was told (1) that the valve is not adjustable, (2) that it is only there for safety reasons, and (3) that it is set at 15 bar by the factory. 15 bar! I'm not sure I believe this. And obviously it is adjustable. But if NS sees this as only a safety feature and does not encourage adjustment I can see why they would not worry too much about its placement.
I cranked the heat up because my crema, though pretty thick, was very pale. Schomer's book and other sources indicate that this is often caused by low brew temperature, and I have read that in NS's opinion a lower brew temp than what is recommended on these boards is ideal. Now the crema is much darker and flavor is more pronounced. I hope soon to pin down the range of the brew temperature to fine tune this adjustment.
I have tried cooling flushes from 2 to 8 ounces and it never seemed to make much difference. But with my new higher temp I will revisit this.
Regarding the pstat range, I am in the process of acquiring the parts necessary to PID the machine, either very cheap or FREE! That should really cut down the cycle.
hifi_guy Senior Member Joined: 4 Apr 2004 Posts: 266 Location: Germany Expertise: I love coffee
Espresso: Simonelli Oscar & Personal V Grinder: Simonelli MDE, Ranc.MD50,... Vac Pot: none Drip: Melitta Cone, now unused
Posted Sun Jan 2, 2005, 5:08pm Subject: Re: NS Oscar Questions (repost from wrong forum)
Happy New Year first of all...
The adjustability (or lack thereof) of the Oscar's OPV has been discussed earlier, and I've read a lot of times that it isn't adjustable. Judging from the OPV's placement, I would tend to agree that the designer has only thought of this as a safety feature, not a way of controlling brew pressure.
The factory setting on mine was 15bar – at least! There was never a single drop of water coming from there, even when backflushing with a blind filter.
I think, IF everything is perfect – freshness, grind, distribution, tamp, temp – you should be fine with just about any OPV setting. In another, more recent thread this is pointed out nicely. But when you're just a little bit off to the ristretto side, you will get agressive taste and a tendency toward channeling and overexctraction, while with regulated brew pressure you might simply end up with a perfectly acceptable, nice cup of ristretto.
But maybe NS are right: maybe opening the OPV (It definitely IS adjustable and works consistently...I've just checked it this morning) also opens a new set of problems. For what it's worth, my shots have changed in character, but haven't improved in overall quality. But hey, I'm still workin' on it.
Bernhard
Oh, and yes, I use the stock double basket. Haven't used the single in a while, as to my understanding it should be impossible to adhere to the "golden rule" when using a single on an non-brew-pressure-regulated machine.
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