Dishwasher Tripping RCD Adaptor

Discussion in 'Electricians' Talk' started by j0nr, Nov 7, 2021.

  1. j0nr

    j0nr New Member

    Hello all,

    I have an integrated Bosch SGV46M03GB dishwasher. Probably quite old, was already in the house when we moved in 3 years ago.

    Recently started tripping the RCD adaptor (plug in one, not integrated) mid cycle.

    I have changed the RCD, no difference.

    I have changed the heater element, no difference.

    If I run it on a rinse cycle, I believe no heating is involved and it runs OK. But any cycle where it warms up it trips.

    After it has tripped I have to wait for it to cool down before the RCD will reset.

    Can anyone offer any other suggestions to try please? Inside (underneath where pumps etc are) looks clean, no signs of leakage.

    Many thanks
  2. Wayners

    Wayners Screwfix Select

    Hade you checked all wires are tight (best remove and put back) in sockets and fused spur? Look for any melting. Had one last year kept tripping and could not pull fuse out the spur draw as melted. Probably like it for ages and causing random trips.

    As for dishwasher have you watched Charliediy on youtube dishwasher repair?
    That's all the help I can offer
  3. seneca

    seneca Screwfix Select

    Sounds like the heating element is faulty.
  4. j0nr

    j0nr New Member

    Hi Wayners,

    My understanding (which might well be wrong) is that an RCD trips when it detects an earth leak in the appliance. I will have a look inside the socket though.

    Seneca, I have already changed the heater element. It wasn't that.

    I think something else may be drawing too much current and when the heater is on and the other "thing" it overloads the RCD.

    I'm not quite sure how to narrow down which component might be faulty.
  5. Wayners

    Wayners Screwfix Select

    Was only live wire not seating nice and tight in spur causing trip. I don't know how these things work but must be resistance too high when pulling power and it can sense it.

    Have you tried running extension lead off another circuit to run washer or maybe another plug socket in kitchen?
  6. Tony Goddard

    Tony Goddard Screwfix Select

    Dishwashers have, for purposes of water heating, a "Torribar" type element, that was Hotpoints original tademark for it in the 20's, now more commonly called a mineral insulated element.

    This consists of a tube, made of copper, stainless steel or incalloy with the element wire running up the middle, the space between element and tube is packed out with Magnesium Oxide, which forms the insulation.

    Over time this powder insulation can take on moisture from the air, causing a fall in IR, which is a very common cause of nuisence tripping.

    This elements can have a cold IR of anything from 1 Megohm to infinity, but often less than 10, when fully hot usually infinity or close to - however, if it has moisture on board as the element passes the dew point in its heating cycle, sufficient moisture is present throughout the insulation to allow a very low IR to occour and hence leakage. When hot even a faulty element will test out Ok as this moisture is driven to the outer edge of the insulation. The best test procedure is to use a Clamp Meter to measure leakage throught the "heating up" cycle.

    There is a way of fixing the element by cooking it, but it is a right faff and only worth doing on elements that are not available anymore so its the only resort.
  7. Bazza

    Bazza Screwfix Select

    RCDs do not trip because of too much current they trip because of an earth fault.
  8. j0nr

    j0nr New Member

    So maybe something inside is getting wet?

    I have a multimeter, just not sure what to check.

    I'm gunna go in again and check all connections I can see.
  9. Bazza

    Bazza Screwfix Select

    To properly test an earth leakage you need an insulation resistance tester. This checks the device under high voltage conditions (up to 1000 volts!)
    A multimeter won’t do that.
  10. j0nr

    j0nr New Member

    Hmm OK. I might have to bite the bullet and get someone in to look at it. Just hate paying for something I could do myself.
  11. fred812

    fred812 Active Member

    Had similar once but still still under warranty. Found that some seals were leaking causing dampness underneath and consequential earth leakage. As far as I remember just the seals were replaced, no components and problem went away.
  12. Tony Goddard

    Tony Goddard Screwfix Select

    As I said before, faulty heating element, no question - not an expensive part and normally easy to fit.
  13. Bazza

    Bazza Screwfix Select

  14. Tony Goddard

    Tony Goddard Screwfix Select

    Ah, fair enough, i'll get my coat!!!:confused:

    If only happening on heating check all the wiring associated with the element for damage or signs of overheating.
  15. Wayners

    Wayners Screwfix Select

    Go look up the secret test code. (engineers test cycle) not really secret now we have Internet. Ha.
    It runs through a cleaning cycle using everything in a matter of minutes and with any luck you will find out at which point it trips.

    Washing machines will do the same. Our washing machine will run though fill. Drain. Heat and spin in under 6 mins and looking online dishwashers will do the same.
  16. fred812

    fred812 Active Member

    He's already changed it.
  17. fred812

    fred812 Active Member

    The fact that it's happening when heating is just related to the loading and max earth leakage not necessarily that the component is faulty.
  18. j0nr

    j0nr New Member

    OK so I think I have narrowed it down.

    I stripped the Co trol board out of its plastic housing and bingo, there was a desoldered leg on one of the relays. I resoldered it and thought I'd done it. It ran for a lot longer this time, but then it still cut out. So it feels like it is the control board.

    Trouble is the control board module replacement is like £250+ wtf? That's half the price of a good new machine! How is that encouraging people to not throw perfectly good things away? It's not even anything special looking, just a pretty ordinary looking PCB.

    Might try replacing just the relays...
  19. Wayners

    Wayners Screwfix Select

    Run solder iron over board just incase it's a dry joint on a component
    j0nr likes this.
  20. Bazza

    Bazza Screwfix Select

    You correctly posted this:
    I fail to see how a dry joint can cause an earth fault. An RCD doesn't trip when no current flows (ie a dry joint). An RCD doesnt trip if too much current flows.
    Changing the relays is just going to soak your leisure time.

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