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Topic Title: zs on sockets lower when washing machine running.
Topic Summary: any suggestions as to why
Created On: 02 April 2012 09:34 AM
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 02 April 2012 09:34 AM
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aligarjon

Posts: 2926
Joined: 09 September 2005

ive just been checking the calibration of my loop tester on a known socket at home. ive had pretty well the same reading for 4 years. Today i have just taken a zs reading that was 0.12 ohms lower than my other readings. I went round a few other sockets in the vacinity to see what i was getting and all about the same. As i was there the washing machine in the utility room stopped running as it had finished, i took another reading from the original socket and it was back to where it usually is . i went round the others and they are all correspondingly higher. I am pressuming the washing machine or a larger load in general effects the readings. maybe due to voltage fluctuations depending on size of load ?


Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
 02 April 2012 09:41 AM
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dg66

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Or maybe a parallel resistance to earth via the load(live to neutral) assuming a TNC-S supply.

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Dave(not Cockburn)
 02 April 2012 10:38 AM
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Boyobach

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Maybe it depends upon the type of load i.e whites or colours!
 02 April 2012 02:32 PM
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mikejumper

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Originally posted by: Boyobach
Maybe it depends upon the type of load i.e whites or colours!

It could be that they weren't harmonised colours.
 02 April 2012 02:51 PM
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John Peckham

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Loop impedance testing should ideally be carried out on installations that do not have any loads connected. Your washing machine is probably generating all sorts of noise and harmonics which will impact on loop readings. If you are using a low current test you will get more reliable readings from a fruit machine.

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John Peckham

http://www.astutetechnicalservices.co.uk/
 02 April 2012 06:45 PM
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perspicacious

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Think about what an EFLI tester measures......

Hint, what does a mercury in glass thermometer measure?

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BOD
 02 April 2012 07:09 PM
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dg66

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EFLI tester measures impedance,thermometer measures temperature.I deduce that with a load on the circuit the temperature of the conductors increases so the impedance should increase not decrease as stated in the OP.

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Dave(not Cockburn)
 02 April 2012 07:13 PM
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Rulland

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I deduce that questions shouldn't be answered with questions!,we all have our threshold on knowledge-hence the op's original post!.

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Those who make no mistakes do very little work!!......
 02 April 2012 08:53 PM
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perspicacious

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"EFLI tester measures impedance,thermometer measures temperature"

In simple terms, a mercury in glass thermometer measures the expansion or contraction of the mercury volume into a narrow tube which has numbers on it representing temperature.

In the same vein, what does your vehicle fuel gauge measure?

Again in simple terms, an EFLI tester typically measures voltage drop during part of a sine wave cycle by applying 10 Ohms (ever noticed the house lights flicker when pressing the test button?) and equates this to EFLI.

If during the short test period, the sine wave is not true but subject to distortion by external influences eg thyristor drives, the result is unlikely to be accurate (well as accurate as EFLI testers can be to pre-empt a colleague's expected comment)

Regards

BOD
 02 April 2012 09:31 PM
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Rulland

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Better , Thank you Bod.

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Those who make no mistakes do very little work!!......
 02 April 2012 09:39 PM
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perspicacious

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"I deduce that questions shouldn't be answered with questions!,"

And I believe that it shouldn't be handed to you on a plate so as to encourage life long learning (CPD anyone?) beginning with the very well written Ladybird junior science book "Magnets, bulbs and batteries" whose introduction reads: "With simple text and fascinating coloured illustrations this first Ladybird Science Book introduces a child to the principles of electricity and magnetism. This vital subject is explained by simple experiments and working models..............It is the perfect introduction to science, and to the scientific way of thinking."

Regards

BOD
 02 April 2012 09:56 PM
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Rulland

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I take it that you have the book?,do you have to refer to it often? .

Regards.

Richard.

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Those who make no mistakes do very little work!!......
 03 April 2012 08:55 AM
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perspicacious

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"I take it that you have the book?,do you have to refer to it often?"

Of course, as proven here

What are the generation brought up on smart phones going to be able to achieve practically?

Regards

BOD
 03 April 2012 07:42 PM
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aligarjon

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Thanks chaps. i might pop down the library tomorrow.

Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
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