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Oscar rebuild and modification

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  • Oscar rebuild and modification

    Hey all,
    After bending the boiler on my Oscar, Ive decided to pull him apart, bathe all the components in descaler, rebuild and make some modification while Im there!
    The mods I want to do are:
    1. Reposition the OPV
    2. Install anti-vac valve
    3. Boiler pressure gauge
    4. Musica flow restrictors in the group

    I have dreams for the following, with the likelihood of actually doing them in descending order:
    1. Brew pressure gauge
    2. Brew temp readout
    3. Hot water wand

    Well leave the dreams for later, as at this stage, theyre definitely dreams.

    Regarding the OPV. My plan is to move the current Neplax valve from its position at the group to behind the HX somewhere (And obviously plug the hole in the group with a bolt).
    1. Any thoughts on why they would place the Neplax valve at the group? My thought was that it is a pump safety valve so that the pump isnt overloaded. Any other reason? The Musica, which uses the same group, has the same Neplex valve at the group, set to 16bar, as well as another valve before the HX set at 10bar.
    Would I be messing something up by moving it? I can just buy another from the Simonelli distributer, but it seems unnecessary as it will still cycle water out to save the pump if its before the HX.
    2. Where would be better to put the OPV - After the pump and before the 2-way, or after the 2-way and before the HX? I have seen people out it before the 2-way, as per the pictures below (tpowells of coffeegeek), but my thought is after the 2-way and before the HX, because if the boiler has to fill during the brew, this might be nicer to the consistency of the brew pressure. Does it make a difference? I have seen people out it before the 2-way, as per the pictures below.

    Thanks ill be sure to post up lots of pics and details of the rebuild!


  • #2
    Re: Oscar rebuild and modification

    Originally posted by 414A464E585B494E4A58474E522B0 link=1320798434/0#0 date=1320798434
    1. Reposition the OPV
    Whoa! Dont do that - the "OPV" in the HX loop is to vent excess pressure in the loop. Consider what happens when you heat the HX loop - the water in it expands! It has to go somewhere This is a primary safety device!

    The correct solution is to put an OPV in the pump circuit. My plan is to splice in an OPV around the pump - excess pressure feed back into the input side.

    I plan on your dream #2 soon - I have a PID to use as a temperature readout, and your #2 mod

    For the #2 mod - what Im planning on doing is whacking in a T for the steam outlet and putting a low profile anti-vac valve on the top of the T with a 32mm diameter copper pipe end cap as a "cup" to catch the bit of water that will inevitably dribble out.

    /Kevin

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    • #3
      Re: Oscar rebuild and modification

      Thanks Kevin - PID would be cool!

      Now question... I just received my new boiler, bought it from the Nuova Simonelli distributor here, and it seems to have scale and / or copper corrosion inside and on the fittings - as you can see in the picture.
      Is this expected from a new boiler? Is that just what copper does? If it hasnt been used before, does that mean it would have been sitting around for a really long time?
      Could it be a 2nd hand boiler? It seems like the insulation around the boiler is new, but from the fittings and the inside - well I dont know.
      Any thoughts before I call the distributor back and ask them?









      Comment


      • #4
        Re: Oscar rebuild and modification

        That boiler looks new to me...

        Comment


        • #5
          Re: Oscar rebuild and modification

          Ok - so the green stuff around the fittings and the little bit of white crud inside is just standard stuff that builds up on copper?
          Should I clean it off or just leave it?
          Also - that insulation thats on there, it seems like rubber tube with some thick aluminum foil type stuff in between - is that good insulation? I bought some insul-brite to insulate it... maybe Ill just double insulate it!

          Comment


          • #6
            Re: Oscar rebuild and modification

            Just give it a little clean with some water. I would leave the insulation as it is.

            Comment


            • #7
              Re: Oscar rebuild and modification

              Thanks James - sounds good, Ill give it a good clean before popping him in.

              Well there has been a lot of work done on little Oscar. We began with a very poorly treated machine. No malice, just no idea really. Goes to show that you should never buy a machine unless:
              a) Youve done a fairly thorough inspection, or;
              b) Its a ridiculous bargain to offset the work that you will undoubtedly have to do.

              I started by cleaning up some very grotty looking copper and brass with some serious scale in some parts in a good bath of descaler - and they came up looking great!

              I have been looking at Marcio on his HB thread of his Oscar restoration:
              http://www.home-barista.com/espresso-machines/nuova-simonelli-oscar-rebuild-t13832-10.html
              He said that the rising temperature profile of the Oscar was sorted out by 3.2mm and 3mm flow restrictors inserted into the group inlet and outlet - as per the Musica which has the same boiler, pipes and group.
              So after an order from the NS distributor (including the new boiler and expansion valve), and after a quick walk over to the tech department at school - we have threads in the group and gigleurs in!

              Theres more stories and photos to come...









              Comment


              • #8
                Re: Oscar rebuild and modification

                looking great! good to see you getting your hands grubby and getting in to it. Agree about a good machine inspection or allowing funds for repairs if required, etc.

                Very interesting about the restrictions, will be watching your thread

                Comment


                • #9
                  Re: Oscar rebuild and modification

                  Originally posted by 646F636B7D7E6C6B6F7D626B770E0 link=1320798434/2#2 date=1322169952
                  Thanks Kevin - PID would be cool!
                  Its just for the temperature display of the grouphead! I havent actually "gotaroundtuit".. But - the plan is to tap an M6 thread into the group head and screw in a PT-100 sensor. Ive got the 1/32nd DIN PID controller and the sensor. I would use a temperature readout device, but the PID is about the same cost and a heck of a lot simpler to wire in (it is 240VAC). I plan on putting it next to the steam control under the buttons.

                  Since youve got your machine in atomic sized pieces, doing something like this now would be straight forward. Drilling and tapping the grouphead isnt something you can do in-situ (at least, you cant tap - unless you can lay hands on an extra-long tap!).

                  /Kevin

                  Comment


                  • #10
                    Re: Oscar rebuild and modification

                    Originally posted by 7B707C746261737470627D7468110 link=1320798434/2#2 date=1322169952
                    Thanks Kevin - PID would be cool!

                    Now question... I just received my new boiler, bought it from the Nuova Simonelli distributor here, and it seems to have scale and / or copper corrosion inside and on the fittings - as you can see in the picture.
                    Is this expected from a new boiler? Is that just what copper does? If it hasnt been used before, does that mean it would have been sitting around for a really long time?
                    Could it be a 2nd hand boiler? It seems like the insulation around the boiler is new, but from the fittings and the inside - well I dont know.
                    Any thoughts before I call the distributor back and ask them?
                    All of the "residue" you can see, is as a result of some remaining flux after manufacture, reacting with moisture in the air and the copper. You can neutralise this by flushing liberally with a gentle Sodium Bicarbonate water solution. Its nothing to really worry about though, just looks a bit messy....

                    Mal.

                    Comment


                    • #11
                      Re: Oscar rebuild and modification

                      Thanks Mal
                      I made up a mild citric acid solution (1tbs / 1.5L) in hot water, sealed up the holes, poured it in and gave a swirl all over for about 2 mins, then drained and clean water flushed - and it made a big difference!
                      Im guessing (hoping) thats similar to the Sodium Bicrab solution? Seemed to work anyways!

                      So annoying... I put him all together and plugged back in for the first time today - only to find that after the new anti-vac valve closed and he was building up pressure, there were some faint steam leaks from some of the fittings - obviously not enough plumbers tape Oh well.
                      Pulled the boiler out again and re applied, but ran out of time to test, so will do tomorrow!

                      Comment


                      • #12
                        Re: Oscar rebuild and modification

                        Originally posted by 3239353D2B283A3D392B343D21580 link=1320798434/10#10 date=1322296240
                        Im guessing (hoping) thats similar to the Sodium Bicrab solution? Seemed to work anyways!
                        Well, not really the same but if the Citric Acid did the job and all is OK after a good flush out, then all is well.... 8-)

                        Mal.

                        Comment


                        • #13
                          Re: Oscar rebuild and modification

                          Grrr... after putting him all back together and pulling back apart 3 times after finding little leaks, this silly little broken part thwarts my weekend. So Oscar remains unfinished.
                          Sucks

                          Comment


                          • #14
                            Re: Oscar rebuild and modification

                            The part is a retaining valve, aka non return valve or one way valve. My understanding is that it stops the hot water from the heat exchanger going back down the line to the solenoid valve. Its noted as the little part in the middle of the red circle on the diagram.
                            Now... the boiler fill tube and fitting doesnt have a retaining valve, so the hot water from the boiler can travel back down the line to the 2-way valve, as shown in the blue circle.
                            This seems strange to me, as I would have thought it would need one, and am thinking about putting one in. In an ideal world, should it need one to stop the boiler water going back to the 2-way solenoid, or does it not really matter?

                            Comment


                            • #15
                              Re: Oscar rebuild and modification

                              Isnt the blue circled bit the boiler drain bit?

                              The boiler fill, and the HX pumping bit is done via a valve that shifts the inputs. So there only needs to be one non-return valve.

                              Bit of a bugger that it broke though. Makes me fear for the weekend when I pull mine to bits :-/

                              /Kevin

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