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Why are there 2 OPVs in the Giotto PP v2?

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  • Why are there 2 OPVs in the Giotto PP v2?

    Hi all

    I'm confused by the layout in my Giotto PP v2. (Aussie bought, about 18 months old)

    Per the attached pic, there are 2 OPVs on the HX path. I searched the usual sources and can't find a schematic which matches this layout.

    The OPV just to the right of the water tank inlet is the usual OPV position, and (I believe) is the final stage before water enters the HX. But the OPV on the left of the pic is the one that confuses me. The Ukla pumps into the bottom of the rectangular brass valve (which feeds the pump pressure gauge) and then outputs through to the main OPV and into the HX.

    But what does the OPV on the left side do? Any why is there a tap at the bottom of it? (Which is turned on)

    Cheers
    Jonathon
    Attached Files

  • #2
    I expect Talk_Coffee will probably respond here, but you're right, it seems a bit odd.

    Looks like the OPVs are in "series", it also (based on thread exposure) seems that they are set to two very different settings. Turning off the tap on the left hand OPV would take it "out of circuit", two stages of OPV? Though it looks like a fairly standard Ulka 5 pump in there so I'm not sure why it'd be necessary...

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    • #3
      It's hard to tell from the pic, but they do not appear to be in series to me. I'm guessing one is for brewing (on the right) and one is downstream of a solenoid valve (on the left), which feeds the boiler.

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      • #4
        Originally posted by jbrewster View Post
        Looks like the OPVs are in "series", it also (based on thread exposure) seems that they are set to two very different settings. Turning off the tap on the left hand OPV would take it "out of circuit", two stages of OPV? Though it looks like a fairly standard Ulka 5 pump in there so I'm not sure why it'd be necessary...
        Yes that's my view as well. Assuming they're the same type of OPV, the one on the left is set to a much lower pressure than the 'main' OPV, so I wondered if it's some kind of pre-infusion mechanism, but I can't see how it would be activated, there doesn't seem to be a 2-way solenoid in the path.

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        • #5
          Originally posted by MrJack View Post
          It's hard to tell from the pic, but they do not appear to be in series to me. I'm guessing one is for brewing (on the right) and one is downstream of a solenoid valve (on the left), which feeds the boiler.
          The one on the right is definitely brewing (I think) as it regulates the tube entering the HX, and this is very consistent with all Giotto diagrams I have found so far.

          I also thought maybe the one on the left is boiler-related, but the brew pressure gauge comes off the rectangular valve that it's connected to, so I assume it's HX related.

          As I can't see this layout in any other pics, I'm wondering if it was some kind of trial layout? Or maybe all the V2s are like this?

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          • #6
            Pressure gauge is upstream of the opv, so will always read the pump pressure. Can you follow the outlet piping from the OPV on the left?

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            • #7
              Originally posted by MrJack View Post
              Pressure gauge is upstream of the opv, so will always read the pump pressure. Can you follow the outlet piping from the OPV on the left?
              Yes it goes back into the water reservoir, just like the OPV on the right.

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              • #8
                Originally posted by Jonathon View Post
                I also thought maybe the one on the left is boiler-related, but the brew pressure gauge comes off the rectangular valve that it's connected to, so I assume it's HX related.
                Yeah, the brew pressure gauge being tapped off there threw me too.

                Looks like the ulka only feeds the bottom of the "manifold" the left hand OPV hangs off (thus the brew gauge reads pump pressure), then a rigid line feeds out there into a tee (not sure where the feed from the "down" line of the tee (via the solenoid) goes), the other side of that tee also feeds the right hand OPV which then feeds the HX.

                Actually looking at it again I'm thinking that others may be right, maybe the lefthand OPV is for boiler feed, it would make sense since it's set much lower, must be a check valve in the "manifold" though or brew pressure would bleed through the left hand OPV.

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                • #9
                  The diagrams I have seen before don't include the one on the left, so I - like everyone in this thread - don't really know.

                  Looks to me like water comes out of the pump, through the left OPV which regulates the water from the pump to 9 bar - eg this is the main OPV (controversial I know....) - because the brew path pressure gauge is downstream of this OPV.

                  Then as we go down the path, the like the boiler fill solenoid is the little black box just behind the white tank joiner, so the first OPV is regulating the water going to the boiler as well. Then we hit the 2nd OPV (the one on the right), to which I have 2 assumptions at to what it's there for...
                  1) not doing much except acting as a second line of defense, or possible
                  2) and/or there to assist in combo with the left OPV when boiler refill and brew are happening at the same time to minimise pressure drop at the group. Also informing this is that both OPVs overflow back into the water passage just after the pump.

                  Sorry for no concrete info, I just wanted to exercise my problem solving skills for a couple of minutes - how well did I do?

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                  • #10
                    Originally posted by Jonathon View Post
                    Yes it goes back into the water reservoir, just like the OPV on the right.
                    Sorry, you'll need to follow the other line, not the bypass line.

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                    • #11
                      Originally posted by MrJack View Post
                      Sorry, you'll need to follow the other line, not the bypass line.
                      Gotcha - the water path is from the ukla, through the deaerator, into the bottom of the rectangular brass thingy (what is it?) which has the left side OPV on top of it. The water contines out the front end of the brass thingy via a copper pipe and through the 2-way solenoid, with HX water continuing into the second OPV and boiler water going into the boiler.

                      I'm sure somebody is reading this thinking I've got it all wrong - please do tell me if I have, but that's my understanding of the machine so far. It would be easy if it had the standard Giotto water flow, but for whatever reason this one seems different.

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                      • #12
                        Some success in tracking this down - in this HB post on the Cellini v2 it looks like the Cellini has the same path, albeith the rectangular brass is on its side, compared to in the Giotto. Also, the OPV on the Giotto is larger than the one in this Cellini photo, but otherwise it looks very similar.
                        OPV on Rocket Cellini V2 is confusing. - Espresso Machines • Home-Barista.com

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