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Nuova Simonelli Oscar direct connect OPV

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  • Nuova Simonelli Oscar direct connect OPV

    I have an Oscar that is plumbed in and I purchased an OPV kit a while ago but never fitted it due to some speculation that there would be problems with the pressure being released to the already pressurized supply side of the pump. (1.5bar) I had a look at the direct connect Musica hydraulic diagram and it looks like the opv is plumbed the same for the tank version and the direct version with the pressure relief being directed to the intake side of the pump.
    I have just had my HX split inside the boiler of my Oscar and feel that having the neplex valve at 16.5bar governing the pressure of the HX side it may have put the HX under too much stress so I would like to install the OPV if possible when I install the new boiler. Has anyone any experience with this type of OPV installation?


  • #2
    I installed a Oscar opv kit into my Musica. Although mine is tanked, I suggest setting the opv will be similar, though it will be slightly different because you will have your 1.5 bar holding the opv shut. Effectively you will need to reduce your opv adjustment (compared to a tank setting) to get your brew pressure set.

    But you are asking about the neplex setting..
    So your pump will put out (10bar opv setting) into the hx. The only way this can increase is if you stop the shot, and the 3way doesn't open, and then the boiler heats the hx another 6bar (is that like 60°?). It could pressurise the hx, as it has a 1way valve after the pump.

    But, I think it will be fine. You are getting a opv to actually lower the brew pressure, so now with a 16.5 bar neplex, you have a heap more headroom. The neplex is only a safety anyway....
    However, if you are concerned, I think the Musica neplex it set lower, or I think you can shim the neplex body to reduce the spring pressure, so lowering the neplex.

    Ah, I remember... The Musica has a neplex at 16 odd bar, but has a 11bar pressure valve after the pump. This could be interchanged with the neplex.


    • #3
      Hey Jackster,
      Thanks for the reply. I wasn't really asking about the neplex, was more refering to it being the final controller of the HX pressure in the Oscar's current configuration. I would often have the neplex passing water during a shot meaning that the group head pressure would have been 16bar and I feel that may have contributed to the HX failing. You may be correct about the static 1.5 bar pressure on the discharge side of the OPV meaning that the blow of pressure could be raised by the water supply pressure, but it would still be a lot less than 16bar.
      Did your Musica not have an OPV standard? Did this only come out in the later models? I will rebuild the Oscar but am thinking of buying a new Musica.


      • #4
        Musica is a old one, I think it had a non adjustable valve, I shimmed it as my pressure was low, then replaced it with the Oscar opv kit. It turned out it was the pump having low pressure, nothing to do with the valve...

        I think the testing procedure is 2x pressure, so would have been tested at 35ish bar. Not saying that 16bar didn't kill it, but I think it would only have lasted a little longer if 10bar on it.

        Fit your opv kit when you put the boiler in.
        There is utube videos on how to do it. The Musica has different connections to be made, but it's a pretty easy job.