Question hydraulic path in Oscar Nuova Simonelli

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by smartalek »

Hi all,

I am looking at the schematic of a Nuova Simonelli and I have some questions:

Why (10) is a three way solenoid valve and (3) is a two way valve? For me it is the same symbole, both have two ports so they are both two-way valve?

Also don't understand why the check valve (4) is pointing up and not down? It means the water from the tank cannot pass thought the heat exchanger?

In brew mode, the valve (10) is ON, the pump is ON, the water is coming from both ports of the GH? so there is water coming from two paths:
the heat exchanger but also from the colder pipe? I am assuming there is a small difference in temperature between those ports?

Thank you

Team HB

#2: Post by JRising »

Amusingly enough, in that diagram there are only the 2 ports shown, but in reality it's one of those "lucifer valves" with a square base and 2 ports sealed by o-rings, while the end of the shaft around which the coil resides has a hole in it, a third port...
Thus, when the coil is not energised, the moving slug is held by spring against the port that comes from the heat exchanger, keeping it closed... That leaves the port going to the brewhead open to the drain port at the far end of the valve, so if any residual pressure is in the portafilter, it will drain through the three-way valve... think back-flushing. Then, when the coil is energised, the slug is magnetically held at the far end of the shaft, closing off the port to drain, leaving brewhead connected to heat exchanger, and the sweet espresso is brewed.

So... Pretty good diagram, but it should show the drain from the three-way.

And, check valve pointing up not down... It's not a directional arrow. Imagine it as a funnel with a ball in it, even when the ball isn't shown...
No matter how hard the pressure pushes the ball into the funnel, nothing will flow, the ball is in the way... But going the other way, the ball easily un-seats from the check valve and flow is easy...

And now you can say "But in number 2, the arrow points the other way"... In a circle it's a pump, and one triangle means unidirectional...
It's not a valve if it's not in a rectangle. I don't make the rules, I just look forward to a good coffee.

smartalek (original poster)

#3: Post by smartalek (original poster) »

Thank you so much JRising,
So it means when we fill the boiler, valve (3) and pump are ON, there is also water going to the heat exchanger?

Team HB

#4: Post by JRising »

If the heat exchanger were empty, a small amount of water would flow into the brew circuit until the air/steam in there were compressed to 1.2 Bar, but the heat exchanger is always full of liquid water in a properly working HX machine, so there's really nowhere for water to flow that direction, the brew valve is closed and the liquid is nearly incompressible. The water can easily flow against the 1.2 Bar of the steam boiler so it flows in that direction, the check valve prevents the brew circuit from losing pressure to the steam circuit when the boiler-fill valve is open.

smartalek (original poster)

#5: Post by smartalek (original poster) »

So the pump is only used to fill the boiler? It is not used at all to create the pressure for brewing?

Team HB

#6: Post by JRising »

No, sorry... When brewing, the pump is running but the brew valve is also open, so the pump is providing all of the flow for the brew process. The resistance to that flow, by the puck of coffee grounds, is providing the pressure.
I was just stating that during the boiler-fill routine, the pump isn't filling the heat exchanger because it's already full and there's nowhere for the water to go.

smartalek (original poster)

#7: Post by smartalek (original poster) »

Alright now it make sense thank you very much.

And last question:
During the heating of the GH, the water is circulating like this:

But then when we brew, what is preventing the water to take the path 2, meaning it does not go through the HX, its goes directly from water tank (room temperature) to GH?

Team HB

#8: Post by JRising »

Again, the oversimplification of the diagram you're looking at is confusing you. The actual inlet side of the heat exchanger is an injector pipe inside the large fitting of the thermosiphon circuit.

The cool water is pumped in through that small elbow and is contained inside the copper pipe until the end of the copper pipe deep inside the HX...
The thermosiphon flow flows in through the side of that tee-fitting and up into the HX via convection, outside the injection tube. The tube is tightly sealed inside the small-diameter elbow fitting. (This is assuming that the machine is injecting at the bottom of the HX, Biancas and some Maras do it the other way)

Additionally, there will be a restrictor somewhere in the circuit. It limits the speed at which the thermosiphon flows and also ensures that the water flows faster through one port than the other when brewing... Engineers test various sizes of orifice at various locations to get a good rebound speed and limit the cooling flush time.
★ Helpful

smartalek (original poster)

#9: Post by smartalek (original poster) »

Alright thank you very for those info ;)