Electrical question

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  • S/V Laura Ellen
    Neither Fair nor Balanced
    • Oct 2003
    • 9384

    Electrical question

    I'm confused by some wiring in an espresso machine. The relay shown in the inserted image is chattering.
    Not quite sure what is causing the relay to chatter yet, could be the electromagnet is weak, the contacts are failing (pitted?) or the items the feed voltage to the solenoid are faulty.

    Looking at the wiring diagram I'm not sure what the relay is supposed to do. Any ideas?
    The power cord is in the lower left corner and the relay is in the upper right.

    Allan of the Grove
    "never send a ferret to do a weasel's job.."
  • epoxyboy
    Senior Member
    • Sep 2005
    • 6213

    #2
    Re: Electrical question

    Wow, so much complexity to get a a brew!
    It is unlikely in the extreme that the electromagnet in the relay is weak, although failures where the winding connects to the bobbin at the base of the relay aren't unheard of.
    If the relay is soldered directly into a circuit board, I'd take a look at those connections. Either the soldered joint itself, or the copper track right where the solder finishes can fail, particularly on those brown phenolic substrate boards common in consumer electronics.
    If the relay is hanging off a loom, try wriggling the connector around, or unplugging it a few times, to clean up the contacts - give the wires a gentle tug too, as it wouldn't be the first time a crimp connection only just snagged the end of the wire.
    Repeat the above for all the other wiring too, as the problem is just as likely to be with whatever indicates that the relay should pull in, a temperature sensor for example
    MAKE SURE YOU UNPLUG IT FIRST!!!

    Pete
    The Ignore feature, lowering blood pressure since 1862. Ahhhhhhh.

    Comment

    • S/V Laura Ellen
      Neither Fair nor Balanced
      • Oct 2003
      • 9384

      #3
      Re: Electrical question

      The relay is mounted on the frame of the machine. All wiring is individual wires connectec to the relay with crimped on spade lugs. I'll be replacing the relay since it it past it's expected life span.
      Allan of the Grove
      "never send a ferret to do a weasel's job.."

      Comment

      • epoxyboy
        Senior Member
        • Sep 2005
        • 6213

        #4
        Re: Electrical question

        Originally posted by S/V Laura Ellen
        The relay is mounted on the frame of the machine. All wiring is individual wires connectec to the relay with crimped on spade lugs. I'll be replacing the relay since it it past it's expected life span.
        Relays typically have a design life in the hundreds of thousands of cycles, and chattering would be an extremely odd failure mode - welded shut contacts, or failure to operate at all due melted plastic mecanical bits or an open circuit coil are the usual ways they die.
        I guess it is a cheap enough place to start though, and you might get lucky.

        Pete
        The Ignore feature, lowering blood pressure since 1862. Ahhhhhhh.

        Comment

        • S/V Laura Ellen
          Neither Fair nor Balanced
          • Oct 2003
          • 9384

          #5
          Re: Electrical question

          I still want to know what the relay is actuallt doing. I'm assuming that the two rectangular things by the relay are diodes. It appears to me that the relay just latches itself while the power is turned on at the switch. But why is the relay even needed?
          Allan of the Grove
          "never send a ferret to do a weasel's job.."

          Comment

          • paulf
            Senior Member
            • Jan 2012
            • 6933

            #6
            Re: Electrical question

            Intermittent ground faults get then to flutter as well.
            PaulF

            Comment

            • the_gr8t_waldo
              Senior Member
              • Nov 2008
              • 1363

              #7
              Re: Electrical question

              It just may be that I'm reading this on pad (I can't see the full wiring dig.) but, the relay is probably able to handle the amps that the switch alone can't.

              Comment

              • ejds
                Senior Member
                • Nov 2008
                • 230

                #8
                Re: Electrical question

                Is it an open or enclosed relay. I found a few times bugs or roaches in between the mechanical parts of relays causing a lot of noise.
                Egbert

                Comment

                • epoxyboy
                  Senior Member
                  • Sep 2005
                  • 6213

                  #9
                  Re: Electrical question

                  Originally posted by S/V Laura Ellen
                  I still want to know what the relay is actuallt doing. I'm assuming that the two rectangular things by the relay are diodes. It appears to me that the relay just latches itself while the power is turned on at the switch. But why is the relay even needed?
                  As there are a couple of diodes drawn correctly, more likely your rectangles are arc suppression capacitors. My guess is, the relay supplies the heater for the water, and cycles on and off to keep the water from boiling dry. The heater will be at least 1kW, so quite a high current thing.
                  That is why I suggested looking a little beyond the relay, for the possible cause of it chattering.

                  Eta, I'm on an iPad also, and cant see what is connected to the relay off to the right.

                  Pete
                  The Ignore feature, lowering blood pressure since 1862. Ahhhhhhh.

                  Comment

                  • Syed
                    Member
                    • Oct 2006
                    • 5607

                    #10
                    Re: Electrical question

                    Many possibilities, but I shall check the two diodes connected with the relay coil. If the one parallel to the coil is open circuit relay will chatter and if other one is short circuit the relay will chatter.

                    Comment

                    • Paul Girouard
                      Banned
                      • May 2005
                      • 16591

                      #11
                      Re: Electrical question

                      Is this the same machine that came with the garden hose plumbing connector? Send the POS back where it came from and buy a Canadian made model!!! LOL

                      Comment

                      • epoxyboy
                        Senior Member
                        • Sep 2005
                        • 6213

                        #12
                        Re: Electrical question

                        Originally posted by Syed
                        Many possibilities, but I shall check the two diodes connected with the relay coil. If the one parallel to the coil is open circuit relay will chatter and if other one is short circuit the relay will chatter.
                        Ummm, no. The mysterious rectangle are across the incoming supply. MOV's (surge suppressors) possibly, but diodes they ain't. Period.
                        If they were, there would be a flash of light, a phhht noise, and the stench of crisped components within about twenty thousandths of a second of turning the supply on.

                        If they were diodes (they ain't), and if they were across the coil (they ain't), and one of them was short circuit, the relay would not chatter, it just wouldnt operate.
                        You may be thinking of magnetic latching relays with the split coil windings, where each half of the winding can have a fly back diode to suppress the voltage spike. Again though, a short circuit diode would result in the relay either not closing, or not opening, but not chattering.

                        The only configuration with diodes that might result in chattering would require a two phase supply, with diodes in series with each phase feeding a single coil, with its return to neutral. The diodes would have to be in series with each phase for this to work.

                        Pete
                        The Ignore feature, lowering blood pressure since 1862. Ahhhhhhh.

                        Comment

                        • Syed
                          Member
                          • Oct 2006
                          • 5607

                          #13
                          Re: Electrical question

                          I think the relay coil is on left side.

                          Comment

                          • epoxyboy
                            Senior Member
                            • Sep 2005
                            • 6213

                            #14
                            Re: Electrical question

                            I think the coil might be switched off connector JP8 and the blue wire that disappears off to the right, and the switched output might be the two lines labelled BL that also disappear off to the right.
                            What I know, is that the two mystery rectangles are across the incoming suppy, (black-blue, and brown-blue), and if either of them were diodes, it would be a race between the switchboard circuit breaker and the diode to see who failed first. I'd put my money on the diode, on the very first half cycle it became forward biased.

                            Pete
                            The Ignore feature, lowering blood pressure since 1862. Ahhhhhhh.

                            Comment

                            • Syed
                              Member
                              • Oct 2006
                              • 5607

                              #15
                              Re: Electrical question

                              If my assumption of coils (on left) is not correct then these two rectangles could be two coils which are connected in series.
                              In this case the relay will chatter due to lower voltage or dusty armature.

                              Comment

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