IET logo
 
IET
Decrease font size
Increase font size
Topic Title: 110V Across Chassis of Washing Machine to Adjacent Earth
Topic Summary:
Created On: 05 February 2013 07:10 PM
Status: Post and Reply
Linear : Threading : Single : Branch
<< 1 2 Previous Last unread
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 05 February 2013 10:48 PM
User is offline View Users Profile Print this message


Avatar for gkenyon.
gkenyon

Posts: 4478
Joined: 06 May 2002

110 V between casing of washing machine and other "earthed" components in the building typically means one thing:

The Class I washing machine is not earthed.

This may indicate a broken cpc.

However, even if this results in "perceptible shock", the culprit may NOT be a a broken wire or normal "bad connection", but still the individual is getting a shock from the "noise filter" as indicated above. I came across a number of cases, back in the day when I used to repair washing machines, where if the machine is left permanently plugged in to the socket, corrosion builds up where the earth pin in the plug meets the contacts in the socket.

This would, at first, appear quite danerous.

Another way of looking at it, is that the reason the corrosion has bullt up in the first place, is that the protective conductor current from the machine is very small - these days, would be unusual (and often considered dangerous) to be above 3.5 mA (but this was not always the case).
However, when a real fault current (a few amperes or more) tries to flow, the oxidation matters not one jot !
(Of course, give or take the "average human being" and wet vs dry conditions.)

Which is why this "failure mode" doesn't always show up properly even with a standard "16th" or "17th" tester delivering 200 mA into 0.1 Ohm - but it would to a basic Digital Multimeter.

-------------------------
Eur Ing Graham Kenyon CEng MIET TechIOSH
 06 February 2013 09:47 AM
User is offline View Users Profile Print this message



jcm256

Posts: 1878
Joined: 01 April 2006

Parallel or series RCDs: It depends how the electrician configures his consumer unit, take a look at this picture on page 3, clearly the RCDs are not in series, and they are side by side. However if the main switch was removed and replaced with RCD all other RCDs would now be in series with this RCD.

http://www.nexusinds.com/bg/do...CU_brochure_290310.pdf

Edited: 07 February 2013 at 07:03 PM by jcm256
 06 February 2013 09:27 PM
User is offline View Users Profile Print this message


Avatar for slittle.
slittle

Posts: 3523
Joined: 22 November 2007

But whilst they are in series with the main switch, they are still not in parallel in the nexus picture. As each RCD feeds it's own busbar.

To be in parallel, the L & N out of each RCD would have to be joined.


Back to the OP, I've seen exactly the same fault with a PC and a radiator. The case of the pc was at 120v measured to the radiator. The socket had been converted from a flush single fed from and earthed from metal conduit to a surface double socket and no one had connected the cpc.

Stu
 06 February 2013 09:49 PM
User is offline View Users Profile Print this message



daveparry1

Posts: 6224
Joined: 04 July 2007

To be in parallel, the L & N out of each RCD would have to be joined

That's what I was trying to explain last night Stu, i'm sure that there are people out there that don't know the difference between series and parallel!

Dave.
 09 February 2013 12:41 AM
User is offline View Users Profile Print this message



weirdbeard

Posts: 1556
Joined: 26 September 2011

Hi Dave, and All, sorry to the OP for this digression, but would it be fair to say that it is common to describe one or more rcd's as being in parallel to the the load in a physical sense? I do appreciate the difference between series and parallel circuits, but a double poled rcd does not really have any bearing on a circuit as it is neither a supply element nor load so cannot be used to determine the status of a circuit, ie a double pole RCD is simply 'in circuit' between the load and supply so has no bearing on whether the circuit is described as being parallel or series in the electrical sense?
 10 February 2013 09:32 AM
User is online View Users Profile Print this message



AJJewsbury

Posts: 11493
Joined: 13 August 2003

but would it be fair to say that it is common to describe one or more rcd's as being in parallel to the the load in a physical sense?

I can see that two devices mounded side-by-side might be said to be in parallel in the sense that they are alongside each other - in the sense of parallel lines. It wouldn't say it was a common way to describe them that way though - especially from an electrical point of view.

DP devices can be connected in parallel or series just like SP ones. You could have two DP switches for example - wired in series both would have to be "on" for the lamp to light (logical AND), wired in parallel the lamp would light with either or both in the on position (logical OR).

- Andy.
 10 February 2013 11:07 AM
User is offline View Users Profile Print this message


Avatar for ebee.
ebee

Posts: 5707
Joined: 02 December 2004

I agree with AJJ,

Electrically they are in series.
OK they might be mounted in parallel to each other side by side physically but it`s the connections that declare them parallel or series.

Therefore series in this instance

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 12 February 2013 05:56 PM
User is offline View Users Profile Print this message



weirdbeard

Posts: 1556
Joined: 26 September 2011

Originally posted by: AJJewsbury

I can see that two devices mounded side-by-side might be said to be in parallel in the sense that they are alongside each other - in the sense of parallel lines. It wouldn't say it was a common way to describe them that way though


There's a fair few, for example your post of 1.56 in this past topic:

http://www.theiet.org/Forums/f...id=205&threadid=19646

 13 February 2013 10:03 AM
User is online View Users Profile Print this message



AJJewsbury

Posts: 11493
Joined: 13 August 2003

There's a fair few, for example your post of 1.56 in this past topic:

Oops, so I did

(although in mitigation, mi Lud, one slip in 6 years probably doesn't count as that common ... maybe) I'll try to be more careful in my choice of words in future.

- Andy.
 08 May 2013 05:41 PM
User is offline View Users Profile Print this message



weirdbeard

Posts: 1556
Joined: 26 September 2011

Originally posted by: AJJewsbury

There's a fair few, for example your post of 1.56 in this past topic:


Oops, so I did



(although in mitigation, mi Lud, one slip in 6 years probably doesn't count as that common ... maybe) I'll try to be more careful in my choice of words in future.
.


May I present to the jury more evidence of this heinous crime, that I just noticed whilst looking into something else. In this post the OP attempted to conceal the crime by adding a ? directly after the word parallel in a blatant attempt to conceal the evidence being searched for in the search facility.

http://www.theiet.org/forums/f...tid=205&threadid=45839
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.