Hello,

we have a problem with our Nouva Simonelli Oscar II, it seems so that the temperature is too high, coffee burns and has no crema.
Do you have any idea what should be set on the machine to solve the problem?

You would need to measure your group temperature with something like a Scace thermofilter. That is a heat exchange so you adjust temperature based on the cooling flush before you lock your portafilter in and brew. Crema is also a function of coffee freshness. You may have two issues, inadequate cooling flush and stale coffee.

Try reading HX Love - Managing the Brew Temperature as a good primer.

Our coffee is fresh so this can't cause the problem.
We tried the steps in the article but it doesn't help.
The pouring water is still very hot.

Sorry to bump this.. but I am interested to know the conclusion of your problem as I am considering buying the Oscar II myself.

This is not a good machine, not reliable in time... But there's a pressurestat you can set to lower the temperature. Unless you prefer to waste water with cooling flush stuff...

Unless you have two boilers, a cooling or heating flush (depending on the type of machine) is required to bring brew water to the desired temp on most SB machines. Even with a PID, a SBDU machine would take a very long time to come down from steam to brew temp without flushing (or purging water through the steam wand).

Oscar's an excellent machine that's both thermally stable / controllable and very reliable. Diagnosing problems requires information. In this case, you need to know the actual brew temperature, the beans & roast level in question, etc. Calling the coffee "burned" is also subjective - that term may be a language problem, but we have no idea what it means. Bitter? That does suggest too high a brew temp. But unless the machine is malfunctioning, a longer flush should fix the problem. It can also be that the shot isn't pulled immediately after the flush, letting the HX water content heat up again.

When it's too hot at home in winter I do not open the window until it gets better, I lower the thermostat...

There is a thermal delta between the steam boiler and the coffee circuit. Simply lower the temperature of the steam to proportionally lower the temperature in the coffee circuit. It must be understood that if the group is hot it is because it dissipates calories from the big boiler. The water in the heat exchanger never reaches the temperature of the steam because the cooling is constant, maintained by the circulation in the thermosiphon.

The original plastic pressure switch (if it is this one, not the Sirai) is set to 1.5b. That's way too much for most cafes, it's a setting for Italian-style dark roasted coffee.

Nahal wrote:...I am interested to know the conclusion of your problem as I am considering buying the Oscar II myself.

I've never used the Oscar, but based on what I've read in the forums, it's a price performer among HX espresso machines.

The "HX vs. double boiler" debate comes up frequently. The video in Heat Exchanger vs. Double Boiler Espresso Machines summarizes my viewpoint. I've owned several HX espresso machines and tested many more; I don't mind the extra steps, but I fully appreciate why some might find them tedious. The debate reminds me of the automatic vs. manual transmission debates on car forums; there is no "right" answer, just well-informed opinions.

zeb wrote:That's way too much for most cafes, it's a setting for Italian-style dark roasted coffee.

My rule of thumb is the darker the coffee, the lower the brew temperature, assuming it's an Arabica. I don't have a lot of experience with Rubustas, but I've read reports of using higher brew temperatures for them (e.g., 203.5°F for Espresso Vivace Dolce). For really bright coffees, I use higher temperatures to reduce acidity (e.g., Ethiopian single origins).