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Faema Urania wiring

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  • Faema Urania wiring

    I am in the process of restoring a Faema Urania single group I imported from italy. I am over the real ugly stuff - rust, scale and sheered bolts are mostly behind me now. But now the question of electricity has raised its head.
    The machine arrived with no wiring at all so its been hard to work out how the wiring is supposed to go. I have been looking at other restoration threads but most people do not retain the mercury Pstat and its hard to trace the path of the wires and see exactly what's going on inside the sirai box. Based on my research I have come up with the following wiring schematic, its not strictly a wring diagram, but i find having a few reference images rather than symbols is useful for me. Im just hoping someone here might be able to comment. Is it normal to have the Pstat switch both the Active and Neutral or do you only switch the active?
    Attached Files

  • #2
    wow 150 views and no replays,
    I guess that deserves at least one picture of the rebuild. Im still hoping someone out there will make a comment to confirm what I'm doing is right (or not).
    Attached Files

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    • #3
      Hi Aaron , What you've drawn looks right, but it all depends which mercury pstat you have. If you have the one with two mercury bulbs, then you can switch both wires, but if you have the one with one mercury bulb, just the active (brown) wire. You may also want to wire in a thermal cut-off thermostat between the pstat and element. I usually either mount a screw-in type in the alloy boiler ring, or a surface contact one held in place with wire around the boiler like Paul Pratt does

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      • #4
        Hi Mike, Its the two bulb model. Here's a photo of it when I was putting it back together after cleaning it. One bulb is not attached in the picture, you can just see the mounting clips.

        I had seen those thermal switches on Paul's rebuild threads, they look quite large - almost like a SSR. I had a bit of a look online and couldn't find where to buy them. Are the ones you use the little threaded brass round ones like they use in Sylvias and Pavoni's? what's the temp rating? and where do you position them on the ring? top? middle?

        Also do you have any experience with adjusting these pressure stats? there is surprisingly little info out there about them.
        Attached Files

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        • #5
          The ones Paul uses are the LM 130 degree bipolar , i think;

          https://www.coffeeparts.com.au/parts...tat-with-reset

          You could use the screw in m4 ones, but most of those are 165, not sure if 130 is available in resettable? From memory, turning the big wheel adjusts the pressure set point, the smaller nut is just a lock-nut . Setting them up is a bit of fun, trial and error :-) ...

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          • #6
            Here's a discussion about this very topic on Home Barista. Might be helpful...
            https://www.home-barista.com/levers/...ts-t29313.html

            Mal.

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            • #7
              Thanks Mal, I actually did find that thread.
              It starts off promising, then, as is usual with the internet, it is hijacked by people with no first hand experience of the particular thing you are asking about. It quickly degenerates into "why would you want to use that old thing? youre much better off with a PID."

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              • #8
                Originally posted by Aaron View Post
                wow 150 views and no replys
                Originally posted by Aaron View Post
                I actually did find that thread.
                It starts off promising, then, as is usual with the internet, it is hijacked by people with no first hand experience of the particular thing you are asking about.
                Once you've eaten your cake you don't get to have it anymore

                Nice looking build though

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                • #9
                  I thought it contained enough information to get you started though...
                  This type of device was a very common item many years ago for detecting pressure rise in the free volume (above the cooling oil) of Power Transformers to either switch additional cooling On/Off or direct protection of the txfr.

                  Most of these, require an adjustment between the Aneroid Chamber and the actuating shaft to ensure initial operation is close to where you need it. Fine adjustment is then achieved by moving the knurled circular threaded nut(s) until you achieve the tipping point of the mercury bulb. You may have to jockey between them all in order to get the tipping and reset points exactly where they should be.

                  Can't be any more helpful than that I'm afraid without the device in my hands...

                  Mal.

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                  • #10
                    Thats great Mal, actually between your description and me fiddling with it and the few things I have read, I think we are well and truely on the road. Once I have got a little further with the build and can introduce some actual boiler pressure I will be able to confirm our theories and maybe write up a set of simple instructions. Even though most people tend to just remove them and replace with a sirai

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                    • #11
                      I'm with you mate...
                      Stick with the original p/sat as it is a work of art, in and of itself. And, super reliable...

                      Mal.

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