Switch off delay time before brew on Nuova Simonelli Oscar II

Need help with equipment usage or want to share your latest discovery?
cleofide

#1: Post by cleofide »

Hello,

I have just discovered that you could switch off the 3-4 second delay time before the brew pressure starts to kick in on the Oscar II, despite everything I had read before.

One has to turn off the machine, press and maintain the 2-cup button, turn the machine on again, wait for the red light to flash a couple times, release the button and you're good to go. The water starts dripping as soon as you press the button.

Now... what is the purpose of this x second delay? Is it safe to get rid of it or does it serve a definite purpose?

Silly as it may sound, I feel like I am more able to control my shot without it.

Thanks,

toferabc

#2: Post by toferabc »

Where did you read about this? are there any other not well knowns tips about the oscar 2? I just recently got mine.

I am guessing that the 3 sec delay is when a brew button is pressed. The pump runs and tries to fill the main boiler, when it senses that it is filled, a solenoid is activated and the water instead flows to the heat exchanger to the grouphead.

keys115

#3: Post by keys115 »

The solenoid delay is for priming the heat exchanger system. It's safe to turn it off.

toferabc

#4: Post by toferabc » replying to keys115 »

but is it okay to do this? If say you disabled it and flush 3 sec before a shot. wouldn't there be less water on the heat exchanger? a possibility to run out of water during a shot and maybe higher temps?

keys115

#5: Post by keys115 » replying to toferabc »

Yes, there would be some air in the heat exchanger after a flush and the possibility to flash boil the incoming water if you didn't pull your shot fast enough. It's an advanced setting and in my experience it's still totally safe. I actually manually prime my heat exchanger.

toferabc

#6: Post by toferabc » replying to keys115 »

How do you manually prime your musica? asuming you disabled the 3-4 delay after button press

Santi

#7: Post by Santi »

keys115 wrote:Yes, there would be some air in the heat exchanger after a flush and the possibility to flash boil the incoming water if you didn't pull your shot fast enough. It's an advanced setting and in my experience it's still totally safe. I actually manually prime my heat exchanger.
First off, good find, cleofide. The 3 second dead time is...annoying. Before I do it, I assume this is reversible? :lol:

But, keys115, what is it about a cooling flush that allows air to be introduced to the HX? Does the air enter up through the shower screen as water simultaneously flows down?

Santi

#8: Post by Santi »

Air in the HX explains why it takes ~10 sec to build pressure into a blind basket following a cooling flush, but only ~4 sec following a backflush. However, that's with the 3 sec solenoid delay, so I'm not sure it accomplishes much. With no solenoid open the air can't escape though, right? The vibe certainly doesn't sound like it's pushing water. I guess I don't understand the purpose of the solenoid delay unless it's just supposed to compress the air.

keys115

#9: Post by keys115 »

toferabc wrote:How do you manually prime your musica? asuming you disabled the 3-4 delay after button press
I like to do a water backflush with a blind filter to "wash" the screen before pulling a shot. This primes the HX at the same time.

Santi wrote:First off, good find, cleofide. The 3 second dead time is...annoying. Before I do it, I assume this is reversible? :lol:

But, keys115, what is it about a cooling flush that allows air to be introduced to the HX? Does the air enter up through the shower screen as water simultaneously flows down?

It is reversible, just repeat the same process you did to turn it off to turn it back on. When you do a cooling flush, there is superheated pressurized water that is instantly vaporizing. This vapor comes out the grouphead quickly and then soon enough water does. Now, whether there is air entering the grouphead or just vaporized water, I have no idea how to prove either hypothesis.

toferabc

#10: Post by toferabc »

Santi wrote:First off, good find, cleofide. The 3 second dead time is...annoying. Before I do it, I assume this is reversible? :lol:

But, keys115, what is it about a cooling flush that allows air to be introduced to the HX? Does the air enter up through the shower screen as water simultaneously flows down?
The reason why air can be introduced to the heat exchanger is because there is a flow restrictor or gigleur/giggler just before the heat exchanger. The purpose of this is to ,well, restrict the flow of water through the heat exchanger to achieve stable temperature throughout the extraction. When you do a cooling flush the water maybe under a bit of pressure so when it exits the showerscreen, the supply from the pump through the flow restrictor cannot match the flow of water out the shower screen thus creating a cavity in the HX.

I found that I dont need to do a cooling flush with my Oscar 2. I've checked the temps with a DIY Scace thermofilter and, with no cooling flush, my extraction temp rises to about 93-95c then a slow decline as the shot ends.

I've since disabled the 3-4s delay and find this better with the workflow.