Trouble adjusting pressurestat of Nuova Simonelli Oscar - Page 2

#11: Post by **cafeIKE** » February 15th, 2008, 2:25 pm

He could get a ballpark idea of the pressure by measuring the temperature of the flush water in a styrofoam cup.

Wait 15min between adjustment and measurement.

#12: Post by **jesawdy** » February 16th, 2008, 6:44 am

Here is a solution on an Expobar.... no comment on safety, so use caution and common sense.

Worldman wrote:VS,

Hello! The "wand mounted" pressure gauge is pretty simple and an idea I got on-line. It is an inexpensive tire pressure gauge + a 8" long piece of (IIRC) 1/8" rubber tubing + 2 hose clamps...all bought from a local NAPA auto parts store.

The whole cost me ~$10.

You simply open the steam valve and read the pressure with an HX machine. With a single boiler machine (such as Silvia) you will need to assure that the machine is up to steam pressure by switching the high temp element on and waiting as long as you would to start steaming.

Len

#13: Post by **caeffe** » February 16th, 2008, 1:29 pm

I have an Oscar also. However, my Oscar has the Sirai p-stat which takes multiple revolutions of the adjustment screw to change the boiler pressure.

I've also put together the 2 gauge setup similar to the expobar's linked by jesawdy.

One problem with the tire pressure gauge solution is that most tire pressure gauges available are 0-150 psig. You are trying to check for around 1.3 bar (~19 psig, 1 bar = 14.5 psig) which means with a cheap tire pressure gauge you'll be meausuring at the bottom of the range. You could be off quite a bit at that range of the gauge, especially since you are looking for .1 bar changes.

I used a gauge that is 0-160 psig and I have not gotten a lower range gauge. I think Grainger or McMaster Carr should have some that are in the 0-30 psig range if you want to go that route. The tire pressure gauge soln however will get you in the ball park. You can then use the styrofoam cup and thermometer to check the temp and repeat any adjustments as necessary. For temp measurement I use an Extech MN35 multimeter which has a Type K TC and is ~$20 IIRC.

Once you get the P-stat adjusted you should check your brew pressure and adjust the OPV. My Oscar's brew pressure was at >180 psi so I had to turn down the OPV valve some to get it around 130 psi / 9 bar. You'll need to get yourself a brew gauge setup. Get one of those water pressure gauges at Home Depot (0-200 psi range) along with a couple fittings that'll allow it to attach to your portafilter. You'll need to remove the PF spout. There's a thread here about making a brew gauge, I'll have to link to it unless someone else here finds it 1st.

Good luck - Oscar is a very capable machine and once you resolve your p-stat issue you'll be caffeinated soon enough!

#14: Post by **bobcraige** » February 18th, 2008, 8:59 am

espressoheadyvr wrote:First off when I first adjusted it (because my brew was not hot enough) - it "felt" like it had a stop lock in the thread. ( A point where I could not screw down anymore) - but I seem to made that stop lock disappear; possibly just old plastic or grime build up - I don't know if it's really relevant - but the screw is now totally "screwable" all the way down to the brass steam pressure release part and all the way out.

And is it "normal" for a little bit of steam to be hissing/dripping from the brass pressure stat valve?

No, it is not normal for a little bit of steam to be hissing/dripping from the brass pressurestat. From your description, you have broken the pressurestat when you forced it past the end of its travel. This is why it is leaking and needs to be replaced and then properly adjusted.

#15: Post by **nixter** » June 12th, 2008, 12:24 pm

Hey guys, I've just finished dialing in my brew pressure on my Oscar. It's now down to 145 blind psi, down from over 200! I'd now like to start adjusting my brew temp. I'm in the process of looking for a low psi gauge to attach to my steam wand. Once I have my gauge built though what bar am I aiming for? How does bar translate to temp? ie; 1.0 bar=x deg.

thanks,

nik

edit: ok found info.. https://www.coffeegeek.com/forums/espre ... ines/67205

#16: Post by **nixter** » June 13th, 2008, 1:43 am

So I bought a 0-150psi gauge, (smallest I could find), and I managed to take a pressure reading off the steam wand. I originally used a hose which was rated for the pressure but I guess it wasn't rated for the heat as it blew a hole with a loud BANG and scared the bejezuz out of me! Anyhow it looks as though my pressure cycles between 19-21psi or 1.31-1.44 bar. Normally I hit the brew button when the element light goes out which is when the temp is the highest so now I'm thinking I need a new plan. Either I can try and guess when my element is at the bottom of the cycle and brew then, or I can adjust the Pstat so that the top of my heating cycle is closer to 1.3bar.

Thoughts?

nik

#17: Post by **caeffe** » June 13th, 2008, 8:13 am

At that pressure range with your 0-150 psi gauge the reading will be likely inaccurate. Most gauges are meant to be used in the middle 3rd of its range. In other words, to 19 psig could possibly mean 15-25 psig.

#18: Post by **nixter** » June 13th, 2008, 11:15 am

I having trouble finding a lower psi gauge. Can anyone suggest where online i might find one?

cheers,

nik

#19: Post by **cafeIKE** » June 13th, 2008, 2:08 pm

The machine is a HEAT EXCHANGER. Here's Oscar's innards

The brew water is not the same temperature as the boiler. Typically the inlet on an e61 is about 20°F lower than the boiler and the group exit is another 10-20°F below that. When you pull a shot the brew water is a mixture of the inlet and exit water.

If you want to run the boiler so the brew water is at a usable temperature without flushing, the boiler pressure will be in the 0.5 to 0.75bar [ about 228° to 236°F ] range. Steaming is almost non-existant at that pressure.

Omega, Dwyer Instruments, Ashcroft and a bazillion other vendors sell "low pressure gauge".

#20: Post by **nixter** » June 13th, 2008, 3:37 pm

Good lord. So chances are I'm brewing way too hot? I don't understand why a "consumer" machine would ship with defaults so out of whack. I read and read about these machines and i think I know something, then I don't. Frustrating.

So there's no point lowering my Sirai to where I'll have decent brew temps (after the heater turns off, no flush) because I'll have no steam power, correct? I should be doing a flush of X duration to achieve the proper temp, yes?

I appreciate the help cafeIKE

n

I'm now re-reading the HX love and managing HX brew temps threads. I must have had info overload and forgotten them.