Problems with Nuovo Simonelli Oscar

[miKe mcKoffee]

I'm re-posting the following from Sweet Maria's chat List:

Hi,

this problem should probably be delt with on HB or one of the other espresso sites, but I am currently not subscribed so I will sent it here also.

I have a Nuovo Simonelli Oscar, I have owned for about 18 months, and finally I had to descale the machine. The descaling worked out ok, but after the descaling, it seems as if I get boiling water from the group no mattter how much I flush the machine.

The espresso has lost crema and is of a much poorer quality than before.

Even after 10 seconds of flushing I still get the hissing sound indicating I believe that the water is boiling.

Any ideas on how to solve this problem. My guess is that I should try to change the pressure in the boiler, but how is this done on the Oscar. I am blind so any instructions will need to rely on text no pictures. I understand the basic layout of the machine with the boiler, the autofill sensor and the tubes going from the boiler to the steam wand and to the group, but obviously there are a lot of things inside the machine that I have no ideas on what is there for.

Claus Thogersen

[HB]

I don't have direct experience with Oscar, but what he suggests sound plausible. That is, the HX was badly scaled and thus conducted less heat than it does now. Judging from his commentary, he's never touched the pressurestat, so unless the boiler was badly scaled by a previous owner who continually increased the pressure to compensate, flushing longer and/or allowing less rebound time is the easy answer.

Unfortunately Oscar doesn't have a gauge to check the boiler pressure and it doesn't sound like Claus would be comfortable hooking one to the boiler fittings. While it is a hack, I've heard of Expobar owners using a tire gauge, a length of reinforced rubber brake line, and two hose clamps to connect to the steam wand (no joke). That would give us more information to go on. Of course, another prudent option is to take the machine in for diagnosis and repairs by a certified professional.

PS: Chris' Coffee shows Oscar's Sirai pressurestat on the new model and his FAQ outlines how to adjust the CEME pressurestat (same as Andreja Premium / Anita's). Of course, adjusting requires a boiler pressure gauge...

[HAL9000]

I wonder whether the boiler was descaled as well. If yes, could some scale be interfering with the operation of the p-stat? Could result in overheated water, with the hissing coming from the safety valve? Maybe the pstat can be removed and cleaned? I don't really know how the pstat works, so this is just a swag. Good luck.

[HB]

A mechanical pressurestat is pretty simple; the boiler's steam pushes against a diaphragm that in turn controls a set of contacts. I don't see how scale would foul it, but I'm not a repair technician. A boiler pressure gauge would confirm the pressurestat's proper operation.

[barry]

scale can accumulate on the diaphragm itself, rendering it less flexible.

scale can also accumulate at the connection (more likely), causing an occlusion which delays the transmission of pressure. this will cause large swings in pressure, often putting the boiler in an overpressure condition.

[Woofy]

I suspect there may also be residual scale buildup obstructing valves within the brewgroup plumbing. Low water flow through the brew group may also be contributing the the Oscar's inability to adequately cool its brewgroup during flushing. While we have pretty soft water, Western Washingtonians get plenty of limescale buildup from our water. It would be advisable to descale the Oscar several times, including the brew group plumbing. If that doesn't improve things, I strongly suggest Claus contact the distributor for Nuovo Simonelli in Ferndale, Washington. They have a tech who knows the Oscar quite well and has been quite helpful in my experience. Their phone number is 360-366-2226.