RE: Re: Dishwasher Fault

["Nigel Giddings" <nigel@xxxxxxxxxxxxxx>]

Tim,



Looking at the picture in the link it is the RCD (Residual Current
Device) that is tripping and not the MCB (Miniture Circuit Breaker(black
Switches)) associated with the Kitchen? Ring-main.



What this suggests is that there is an 'earth leakage' issue as opposed
to a short circuit issue... An RCD measures the flow of current in the
Live and Neutral conductors looking for an imbalance. Theoretically any
current passing over the live wire should be the same as that passing
over the neutral wire. If current is escaping (to earth) there is a
fault. The RCD you have fitted is probably a 300mA version, so any
imbalance that exceeds 0.3A will trip this switch. This is a lot more
sensitive than the 32A required to trip a typical ring main MCB under
fault conditions. Devices will leak to earth, especially heaters in
water, Switched Mode Power Supplies as found in computer equipment,
UPSs. This is why the RCD won't switch unless 300mA is exceeded...



The reason I wanted to understand what was tripping is that you may have
another device that leaks to earth, say 200mA, and when the dishwasher
passes through part of its cycle it adds enough leakage to trip the
RCD... It could well be a fault in the dishwasher and I am over
complicating things... but you may want to try running the dishwasher
with all the other appliances / fittings off if that is possible. This
would include things like immersion heaters and other 'fixed' items.



I have had situations in the past where old fluorescent light fittings
have leaked to earth using up some of the 300mA headroom effectively
making the RCD more sensitive to other leaks. This should not be the
case in your situation as your lighting is not protected by the RCD,
only sockets and fixed equipment ( all those items to the right of the
offending RCD.



Hope this makes some sense



Nigel











-----Original Message-----
From: Tim Fletcher Dot Com [mailto:tim@xxxxxxx]
Sent: 28 October 2007 11:08
To: Tim Fletcher Dot Com; ukha_D@Yahoogroups. Com
Subject: [ukha_d] Re: Dishwasher Fault



Nigel,

OK, I am a bit of an ignoramus when it comes to all things electrical.

My main board is like this http://www.memonline.com/mem2.html#1
<http://www.memonline.com/mem2.html#1>

And the thing that tripped was the small red breaker left of centre. It
left us with no power to sockets, but lights were OK and it was
repeatable - With the dishwasher left "as was" it would trip the
breaker
as soon as the isolator was switched.

Yesterday (more in hope than expectation) I removed the offending washer
and took it outside where I removed all the bits I could test and tested
them to the best of my (limited) ability - they all checked out OK - I
didn't test the thermistor because I read a web guide on how to do it
and didn't have the requisite 'O' levels to be sure I was doing it
right.

Anyway following reassembly it ran through a couple of times OK, so I
reinstalled it and it seems OK - That would lead me to think that the
wires might be starting to go - I'll see how it goes and report back.

Thanks,

Tim.


----- Original Message -----
From: Tim Fletcher Dot Com
To: ukha_D@Yahoogroups. Com
Sent: Saturday, October 27, 2007 10:27 AM
Subject: Dishwasher Fault

Well, it does automate the washing up!

Mine tripped the breaker - element appears to be OK (resistance, earth
leakage etc.) but breaker trips. I'm probably out of my depth with this,
but we don't have any appliance repair guys locally (Daventry) so I'd
appreciate any ideas you may have! Also replacement might be difficult
due to the way it is built in.

TIA,

Tim.

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