Help Needed Wiring Power to an Autofill Controller

Discussion in 'Power Electronics' started by BogartMonroe, Mar 22, 2017.

  1. BogartMonroe

    Thread Starter New Member

    Mar 22, 2017
    I got a beat up Espresso machine that the previous owner explained couldn't wire back together after taking it apart for cleaning. But I am also having some doubts about the autofill controller (Giemme MFC2SN).

    I couldn't find any diagrams or datasheets on the controller so I drew one based on visual and electrical inspection of the board along with the datasheets I found for the material. I've spent a few days looking at everything and double and triple checking, however I'm a little bit too nervous to power on the machine.

    According to the diagram on the controller box (CB). Pin 9 should be Neutral and Pin 10 the Hot. However it looks like this would cause a short at Relay 1 between pin 11 ( connected to CB pin 10) and pin 12 ( connected to CB pin 9). Ive been going at this for a few days and can't make sense of it. Im hoping someone can please take a look at the information I have and can help me out.

    Here's a list of whats on the control board that's switching the AC.
    1. Stepdown Transformer: Hahn BV EI 304 3332.
    2. Relay 1: Finder 40.31S
    3. Relay 2: Finder 40.52S
    4. Relay 3: Finder 40.61S
    5. Varistor: Epcos S07 K175
  2. BogartMonroe

    Thread Starter New Member

    Mar 22, 2017
    Also it looks like pin 8 on the controller is unused however this connects to the varistor and the second input leg of the transformer. Will the second leg of the transformer draw power through the varistor that's also connected to the hot and first input leg of the transformer?
  3. Biff383

    Active Member

    Jun 6, 2012
    I could be wrong, but I believe that L line nine is hot in an AC circuit. That would make line ten the N neutral.
  4. BogartMonroe

    Thread Starter New Member

    Mar 22, 2017
    Hmm. I thought about switching 9 and 10 around but the problem i noticed is that it still looks like a short at relay 1 since they meet there with no load. My suspicion is that pin 8 is the hot and pin 10 is neutral. This works out on a power trace of the circuit. However that would make this system neutral switching. Is that normal?

    I think the box drawing is a little confusing and misleading. It really looks like pin 8 should be hot/line

    Thanks for the reply.
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    The bridge rectifier is wrongly wired in the schematic.
  6. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    Swapping the Live and Neutral around isn't going to make it work any different, what is the problem with the machine,?

    Also the circuit is wrong at the bridge rectifier.
  7. BogartMonroe

    Thread Starter New Member

    Mar 22, 2017
    Thanks for the heads up on the BR. I think I've corrected it.
    So to recap, my main problem with the machine is that if I follow the instructions on the box diagram where it looks like pin 9 and 10 are the neutral and line or vice versa, that there would be a short at relay 1 and that the second leg of the transformer is open and then would be nonfunctional.
    Is that correct?


    Additionally, to me it makes sense that pin 8 and pin 10 should be the hot and neutral.

    And I agree that operationally it should make no difference whether one is hot and the other neutral.
    The only difference I see if by switching the hot and neutral on these two pins is whether the controller is then switching hot or neutral at the relays and the rest of the components are then passively receiving one or the other.

    Is it preferable to have it one way or the other?

    To me I thought it was always better to be actively switching hot at the circuit and then keeping the components you might touch "grounded" with the neutral.

    So, my concerns are:
    1. Is there a short at relay 1 and a non-functional transformer if pin 9 and pin 10 are the hot and neutral?
    2. If indeed pin 8 and 10 are hot and neutral then is it preferable for the controller to be switching neutral over hot or is it trivial?

    Thanks again for the previous responses.