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SyracuseCoffee
Senior Member


Joined: 5 Mar 2014
Posts: 28
Location: Syracuse
Expertise: I like coffee

Espresso: NS Oscar
Grinder: Compak K3
Posted Fri May 2, 2014, 5:01pm
Subject: Plumbed Espresso Machine Question
 

I'm modifying a Simonelli Oscar and am troubleshooting a few ongoing leaks and other issues.  Hopefully the owners of other plumbed HX (or DB?) machines may be able to help.

The Oscar has a 2-way solenoid that directs water flow to the HX or boiler.  I installed a T-fitting on the line between the HX and solenoid.  I know the fitting leaks and am fixing that.  But here's my question....

When I open the water shutoff valve (on my counter)  to allow water to flow into my Oscar, I expect it to flow through the pump but I thought water would stop at the 2-way solenoid.  However, water flowed through the solenoid to the HX (and of course dripped from my leaky fitting).  The machine was plugged in but I didn't turn it on.

Maybe I misunderstand how the 2-way solenoid works.  I thought the solenoid directs water into the boiler based on the water level sensor.  Or the solenoid directs water to the HX when there is a "call" for coffee when the brew button is pressed.  When neither the water sensor or brew button require water, then the solenoid stops flow to the boiler and HX.  My incoming line pressure is only 25-30 psi and well below the 70 psi maximum pressure as stated in the Oscar manual.

Am I missing something here?  Is it possible that the solenoid may need a few operating cycles to get "in sync" since I've had the machine apart?
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SyracuseCoffee
Senior Member


Joined: 5 Mar 2014
Posts: 28
Location: Syracuse
Expertise: I like coffee

Espresso: NS Oscar
Grinder: Compak K3
Posted Fri May 2, 2014, 8:52pm
Subject: Re: Plumbed Espresso Machine Question
 

Could this "leak" through the 2-way actually be necessary to allow the group head thermosyphon to work?  Any Coffee Geek technicians out there?
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CoffeeRon
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Joined: 26 Apr 2009
Posts: 753
Location: Eatonville, Wa
Expertise: I love coffee

Espresso: Wega Lyra, Europiccola(still...
Grinder: Macap M7D, Pharos, Vario W,...
Vac Pot: Sunbeam CoffeeMaster
Drip: Melita BCM-4
Roaster: FR SR500,B-1600, SC/TO
Posted Fri May 2, 2014, 9:03pm
Subject: Re: Plumbed Espresso Machine Question
 

Hi Jeff,
Sorry I don't have an answer for you but wanted to say there are a few around here that should be able to help. It is Friday night though, may take a bit of time for  someone to give you an answer. Good luck with it :)
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plindy
Senior Member
plindy
Joined: 27 Nov 2002
Posts: 74
Location: Seattle
Expertise: Just starting

Espresso: NS Oscar
Grinder: SJ Pharos Lido HG-One
Posted Sat May 3, 2014, 3:57am
Subject: Re: Plumbed Espresso Machine Question
 

Direct connect Oscar
My understanding of the Spec / set-up sheet
3/8 water line with shut off
pump to be supplied with a minimum flow rate of 35 GPH , at no more than 70 psi / 4.8 bar

I bothered to calculate GPH 43 ml/sec , 1 fitting away from pump
Water Pressure Regulator , diameter of feed line , adjustment of Over Pressure Valve , = group head  static pressure .
my setup : WPR 25 psi / 1.7 bar , water line Dia 1/4 " , OPV adjusted , = 145 psi / 10 bar static at portafilter with pump engaged

25 psi flows thru the pump , thru the OPV , thru the double union past the normally closed 2way , that would fill the boiler given signal from boiler level probe , down to the HX intake , thru the 1 way valve that separates the intake of the HX from the thermosyphon return , thru the HX into the group head body and normally closed 3way .

a partial press of the brew button opens the 3way to the brew path , a full press will do all of the same and engage the pump .

the 2way only opens a path to fill the boiler with the pump


Howzat
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SyracuseCoffee
Senior Member


Joined: 5 Mar 2014
Posts: 28
Location: Syracuse
Expertise: I like coffee

Espresso: NS Oscar
Grinder: Compak K3
Posted Sat May 3, 2014, 7:39am
Subject: Re: Plumbed Espresso Machine Question
 

Thanks Plindy

So basically the water path to the HX and grouphead is normally open and the boiler fill is normally closed.  This would allow the thermosyphon to operate passively when coffee is not being brewed.   When the water level sensor calls for water, the 2-way diverts water from the HX to the boiler.  That makes sense to me now so my 2-way appears to be acting normally.

On a plumbed system like mine, the entire HX/grouphead water path will be under line pressure, which in my case, is 30 psi max and well below the maximum pressure of 70 psi.
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