What is the advantage of an in-tank overpressure hose?

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TheCappuccinoKid
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Joined: Dec 27, 2016, 2:54 pm

Postby TheCappuccinoKid » Aug 11, 2017, 9:36 pm

Sorry if this is a newbie question, but I need to learn more about this assembly, and its hard to find the answer on something this specific on Google.

Q. What is the advantages / disadvantages of the type of overpressure system shown in the photo?

The story is I have 2 Saeco Aroma's, but I only plan to keep one of them. Each has a different steam assembly design, as they changed the design over the years. The later model includes a hose leading from the steam assembly into the water tank (see photo). I believe this gets activated by spewing water into the tank in high pressure situations. (I'm not positive; it may only be to prevent water leaking into electricals under rare conditions). The earlier model has no such hose. In that model, the brass valve the hose is attached to is completely closed.

There is an obvious disadvantage to the OP hose; it spews dirtied up water into a clean tank of drinking water. Plus, its one more possible source of leakage. What I'd like to know is if it regulates pressure during brewing at all, or otherwise has any effect on the taste of the espresso. Otherwise, is it strictly a safety feature, and am I better off with it or without it?

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Alan Frew
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Joined: Mar 25, 2008, 6:34 am

Postby Alan Frew » Aug 12, 2017, 6:12 am

TheCappuccinoKid wrote:There is an obvious disadvantage to the OP hose; it spews dirtied up water into a clean tank of drinking water.

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No. Water FROM the tank is pushed via the pump into the boiler, then through the coffee at whatever pressure the OPV is set at. If the OPV opens and returns water to the tank, the only place the water has been is through the pump, there is no contamination. It's a feature, not a bug, and saves wastage of tank water.

Alan

TheCappuccinoKid
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Joined: Dec 27, 2016, 2:54 pm

Postby TheCappuccinoKid » Aug 12, 2017, 12:05 pm

I'm confused, because it sounds like you're talking about the main hose in the water tank connected to the pump. This hose I'm referring to is a secondary hose, and is connected only to the steam valve assembly, as shown in the picture. I believe from the design, it outputs (excess) water, and does not intake it, since it is not in line with the pump. I called it an "overpressure" hose, but I'm not entirely sure it outputs water under overpressure conditions. The "OPV" on the Saeco Aroma (aka "Classico"), is a spring and ball affair.

Since Saeco saw fit to only add this 'feature' on some machines, my mission is to find out why!

AZRich
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Joined: Sep 21, 2013, 4:57 pm

Postby AZRich » Aug 12, 2017, 1:55 pm

They have integrated the OPV with the steam valve assembly. You can see your part here:
http://www.shop.partsguru.com/Saeco-Ste ... 018596.htm

It will only return water to the tank when the valve opens if pump pressure exceeds whatever the OPV is set to - 9/10 bar hopefully (and hopefully it is adjustable) . You should never see 'dirty' water thru the OPV back into the tank since it is coming from the boiler. If you do see dirty water then your boiler needs to be cleaned.
Rich
St. Drogo - patron saint of coffee and ugly people!

TheCappuccinoKid
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Joined: Dec 27, 2016, 2:54 pm

Postby TheCappuccinoKid » Aug 12, 2017, 9:29 pm

Ok, I think its a little clearer, but I thought the "OPV" on this machine was the spring/rubber ball assembly in the hollow screw located in the grouphead at the centre of the shower screen (this type of overpressure system is not adjustable). The return hose on the steam valve assembly was done on later models it appears, but both models with and without this hose appear to have the spring/ball assembly in the grouphead. Anyway, what I wanted to know is which system is better for me to keep? ie. Any disadvantages to the model that does not have the return hose?

AZRich
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Joined: Sep 21, 2013, 4:57 pm

Postby AZRich » Aug 13, 2017, 11:20 am

I believe what you are referring to is the boiler valve which stops water from the boiler just running out the group. It would open only when brewing and is not the same as an OPV. I personally would want the machine with an OPV over one without. On most machines you can adjust the OPV with the use of a pressure gauge to set the brew pressure. The NS Oscar has no OPV, but most pump machines do have an adjustable OPV. No OPV generally means you are stuck with whatever pressure is at the puck and you just use grind to compensate.
St. Drogo - patron saint of coffee and ugly people!

TheCappuccinoKid
Posts: 65
Joined: Dec 27, 2016, 2:54 pm

Postby TheCappuccinoKid » Aug 13, 2017, 3:15 pm

By the "boiler valve", I believe you are referring to the spring/ball assembly in the grouphead. Which if I'm not mistaken, is a type of "OPV" and non-adjustable. But if so, I'm not all concerned with that. I'm focusing on the short hose connected to the steam assembly (attached to the right side of the boiler), that leads to the water tank. I'd like to know just under what condition would water pass out of this steam assembly into the tank, why they decided to add this when their previous machines did not have it (because otherwise the machine designs appear to be identical), and if there's any advantage to machine that has this hose on the steam assembly, versus the machine that does not have it.

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AndyPanda
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Postby AndyPanda » Aug 14, 2017, 3:23 pm

The term OPV is generally used to refer to a valve that this machine does NOT have at all. This is not a machine with a 3-way solenoid and OPV valve.

The picture in the OP appears to be a safety valve to protect the boiler (yes, it's a Valve to protect against Over Pressure, but not the OPV most people mean when they use the term). That safety valve shouldn't release any water back to the tank unless the boiler were to somehow get way over pressure. Since that machine has a spring loaded "group valve" instead of a 3-way solenoid - it is almost impossible for the boiler to get over pressure (that "group valve" would have to be stuck closed and the thermostat stuck in the heating position). SO my best guess is that is why they stopped putting the overflow hose on some models - it is not really needed.

TheCappuccinoKid
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Joined: Dec 27, 2016, 2:54 pm

Postby TheCappuccinoKid » Aug 15, 2017, 3:23 am

AndyPanda wrote:The term OPV is generally used to refer to a valve that this machine does NOT have at all. This is not a machine with a 3-way solenoid and OPV valve. The picture in the OP appears to be a safety valve to protect the boiler (yes, it's a Valve to protect against Over Pressure, but not the OPV most people mean when they use the term).


Ok, now I'm getting a reply that makes sense! I know all that, which is why I kept calling it simply an "overpressure system/hose", and people kept referring to it to me as an "OPV". Which I know this machine doesn't strictly have, and such a thing is nowhere seen in the photo I posted. So now I understand the thing I wanted to know: which is what condition would cause water to pass through that hose on the steam valve assembly. I don't know if its impossible... I have actually seen water in that hose.... but there wasn't enough pressure to cause it to eject into the tank. I think if the boiler did go overpressure on the machines that don't have the OP hose, it would just leak some water from the steam valve. I read something about a teaspoon or two leaking here under rare conditions.

Also, Saeco didn't remove this feature... they added it, as its on the later models. Specifically, they appear to have added it when they changed the boiler design from brass to stainless steel. Noticing this made my decision easy: I'm keeping the machine without the overpressure hose, since I'd rather a machine with a brass boiler than a cheaper stainless steel one!

 
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