I recently bought a barely used (but in storage for 2 years) Nuova Simonelli Oscar and I have a Mazzer Super Jolly that I have had for about year with Starbucks Sirena. At first I was impressed with Oscar's power and the espresso seemed decent, at least as good as the Sirena could pull, plus much more steam power. After two weeks I realized that the shots should taste better and took the temperature of the water at the brew head (with a Rattleware milk steaming thermometer in a styrofoam cup without the portafilter in place). To my shock the brew temp of the water was only 160F!

I opened Oscar up last night and adjusted the Sirai pressurestat counter-clockwise six full turns, until it would not turn anymore. The brew temp increased to 180F, but not 201-203F. What should I do now to get the water to the proper brew temperature?

I should mention that I am venting the steam wand after a 5-10 minute warm up. I read that I only need to vent the steam for about 5 seconds until the heater comes on. Could this be the problem? Do I need to vent steam until it runs out?

Thank you for any help or advice!

Marc

Some reference material for you to read:

How I Stopped Worrying and Learned to Love HXs
Seeking low tech way to measure brew temperature
How to adjust an espresso machine pressurestat (boiler temperature)
Proper Adjustment for Oscar's Pressurestat

The styrofoam cup and thermometer temperature test isn't accurate, but it should confirm you're in the ballpark. Given it's used and your low readings, the heat exchanger could be coated with scale. Or the pressurestat setting could be wrong. Or you're flushing too much / too fast, preventing the heat exchanger from properly recovering.

I'd start by verifying the pressurestat setting by hooking up a pressure gauge to the steam arm. Turning up the boiler pressure up without knowing what the current setting is potentially dangerous. Sure, the safety pressure release and/or boiler gasket failure should prevent the boiler from rupturing, but why risk it?


From Elektra Espresso Machine Explodes in Sainsbury's

Hey Marc. In general when working on things that include pressure vessels, it is never a good idea to make extreme adjustments. Sure, the logic may go like this: A smart person designed this machine, a well designed machine wouldn't have an adjustment that could lead to it blowing up, therefore I can adjust this as far as it would go. But that isn't quite accurate, especially since you are not sure of the functionality of all of the other parts. The overpressure valve may not be perfectly functioning and can even have scale caught up in it (if the machine was stored on its side previously, etc) and may not work correctly, I have seen it.

The temp you are measuring, as HB mentioned, isn't accurate. The response time of the thermometer, the speed at which the water cools, etc. I just did the test on my machine, the brew water was 201 and I measured only 180ish out of 3 tests. Depending on your budget, get an eric thermocouple adator, or a scace and then measure. I can hardly believe that the espresso tasted good at anything below 180 btw. So I am gonna trust your palate and guess it wasn't 160. That being said, the pressure of the boiler doesn't really even relate to the temp of your brew water unless you keep all other things (warm up time, flush time, etc). You can hit 200 at .8 bar or 200 at 1.8 bar boiler pressure. All you have changed is the final steady state temp of your HX loop. Do you notice any "steamy" water coming out of the group head after you have let it warm up for about 40 minutes? Have you been letting it warm up for at least 40 min?

Thanks HB and karl_a_hall!

I did not turn the Sirai up all at once. I did one full turn, measured temp, another turn, take temp, etc., until I had done 6 full turns and the screw did not want to turn anymore. I did not consider the danger of the pressure though, so thank you for letting me know.

My brother-in-law has a nice digital instant scientific thermometer and I will borrow that and measure the temperature again tonight. I have a feeling that my thermometer is not accurate. I am no expert, but I have enough of a palate and experience to know that the espresso I've been brewing in the last two weeks is not awful. It has a nice thick crema, however it is a bit sour and lacking a rich/deep body/flavor. I will let you guys know what I find out tonight with the better thermometer. I suppose I should look into making a gauge for the steam pressure as well.

In terms of a cooling flush. I measured the temperature without doing a flush, although when I brew a shot I do a very short flush. I notice boiling/steaming water just for the first 3 seconds or so of a flush and then the water runs smoothly and I stop the flush, grind, distribute, tamp, and pull the shot. I have had to make the grind much finer (than on the Sirena) to get a 25 second shot. Perhaps this is do to the cooler water. And, yes, I do let the machine warm up for about 40 minutes before use.

Thanks for the reference material! I had already read all of that stuff before posting.

Do you think there is something wrong with the Sirai? I haven't descaled or backflushed yet. Could this be an issue?

Thank you both again! I'll let you know what temperatures I read tonight. Please let me know if you have any other thoughts or suggestions.

So long as you are hearing some hissing (flash boiling) during your flush I'd guess your temp is fine. Water boils (in general) at 212 so it's just a matter of how much to flush in order to get down to your desired temp.

Regarding the steam purge, it's only necessary to crack the knob for a fraction of a second. And this only needs to be done when the machine is warmed up from cold. Check that the boiler light is out, purge a tiny bit of steam (the boiler light should immediately turn on) and you're good! The boiler does not have to be out when you do this, it just gives some verification that the purge worked. You can purge the steam at any point in the warm up so long as steam comes out.

If you get steamy hissing at the start of your flush, you are def getting warm enough water (not that Nixter's advice needs reaffirmed, he is almost always on point). Your temp measurement method is def the problem. Obviously the pstat changes have not guaranteed that your brew temperature would increase. It guarantees only that if you wait long enough, your steady state temperature is higher. Even with the boiler at 2 bars of pressure, you can flush it long enough that you will can pull 190 degree water if you want. Turn your boiler back down, give your machine plenty of time to warm up, and get an EricS thermocouple adapter or something similar so that you have a decent idea of the water temp of the water with which you are brewing. There is always a time, at least once every few weeks, where I am totally surprised at the temp my brew water is *actually* at, despite using it regularly for a few years, and paying very close attention to the machine's habits. At the end of the day, nothing made my espresso better than measuring the temp of my brew water.

BTW, how fresh are your beans?

Definitely recommend dialing that Pressurestat back. Nuova Simonelli technicians advise no more than 2 full turns to increase the pressure when flying blind and from factory default settings. You are both flying blind and have no idea if this has previously been adjusted. Purchase a kit with a gauge to find out where you really are with steam pressure, and a descale is called for as well. In addition to making sure to clear the false boiler pressure on startup, this should solve your issues.

Another thing I have discovered with the Oscar is that measuring temp without any properly ground coffee in the basket tends to yield inaccurate results. Maybe the Oscar is more susceptible to it, but the thermal stability design for an espresso machine is based in part or whole with regards to the flow of water. The slower the water flows (i.e. at proper rate for brewing), the longer it is in the boiler, and the hotter it will stay. When measuring with no coffee or flow restriction, you only get an accurate measurement at the onset of the pump starting. After that, the temp plummets.

jlhsupport wrote:Nuova Simonelli technicians advise no more than 2 full turns to increase the pressure when flying blind and from factory default settings

That is probably advice related to the Matter pstats which are very sensitive to adjustment. The Oscar's of recent years (like the OP's), came with Sirai pstats. They are much less sensitive to adjustment.

That may be, but I'm going back to a conversation I had in the 1st half of 2010. I think it was Ben over there, and he may have been thinking of the old Pstat given that Oscar is not exactly their highest priority. Keep in mind that manufacturers have to be much more conservative when offering tweaking advice so as not to get themselves into a liability problem.

IIRC my Oscar with Sirai required 2 or 3 turns just to make 0.1 bar adjustment.