I have a Nuova Simonelli Oscar that I purchased new in 2006 and have been more than happy with it. I am in the process of repairing the Oscar as the retaining valve has exploded and was restricting the flow to the group head.
I have disassembled the Oscar and was thinking of doing some modifications while it is apart.
I would like to add the restrictors to the group head, (07300684 & 07300225) as well as an anti vaccum valve and Sirai pressurestat. I am on my fourth pressurestat now, (Campini) and it is starting to leak.
I am also thinking about an OPV mainly due to the excessive pressure that can sometimes actually wind the group handle off the group head. My Oscar is plumbed in with filters and pressure restriction to 1.5 bar and is normally on 24/7 but In would prefer fitting the anti vac valve and using a timer.
One question that I have is that with the machine being plumbed in, will that allow the inlet pressure to the pump to be raised to 10 bar if that is what the pressure setting of the OPV is when using a blind filter?
I understand that in a tank situation where the inlet pressure is pretty much zero that the released pressure from the OPV will drop to zero also, but I am not sure in a closed system what would happen.
Hope someone can enlighten me.
I thought of doing that and the expansion valve at the group head is pretty much doing that now. That may be the easiest option. The drip tray is not plumbed in to a drain, but I use the waste water to do the preliminary wash of the milk jug etc, so it is not wasted or left full of water.
If the opv was exhausting to the drip tray I imagine it would fill pretty fast if pulling a few shots or back flushing.
OK, so the opv outlet is routed back to the the inlet before the pump? the opv setting would depend on the inlet pressure, change the inlet pressure and you would have to adjust the opv.
You will have to find a suitable hose for the opv outlet, the normal silicone ones are for no/low pressure