Neutral wire lights phase tester

[ShaznMark]

Hey there everyone
I use a little phase tester screwdriver to test for a 'live' wire, to tell which is neutral and live. I am gazumped by an old garage light however that has a neutral cable showing a light on the screwdriver, and another one intermittent. Could they be from an old 2 way switching arrangement or something. I have a multimeter but no idea how to use it to check stuff like this. Any ideas?
mark

 

[andy]

Hey there everyone
I use a little phase tester screwdriver to test for a 'live' wire, to tell which is neutral and live. I am gazumped by an old garage light however that has a neutral cable showing a light on the screwdriver, and another one intermittent. Could they be from an old 2 way switching arrangement or something. I have a multimeter but no idea how to use it to check stuff like this. Any ideas?
mark

1: bin 'tester' screwdriver. there useless.

2: learn how to use multimeter

 

[Steve]

use your multimeter on voltage AC ~

turn off all the lights and whatever else on this circuit.

put the probes between the cable you are testing and a known good earth or neutral. earth wire usually a good bet

your garage light - how many cables are there? try turning the power off to the circuit and testing for continuity between red and black on each cable while someone operates the switch. When the continuity varies, you know you have found the switch wire.

 

[ShaznMark]

Hey crafty I just tried to use my multimeter, set the switch to V~ 200, when I put the black probe to the neutral and the red to the live, there was a bang and I think ive blown a fuse at the CU.

Can I just clear up that a neutral wire should not show a strong bright light on a tester? I am nearly sure it is the cable running directly from the consumer unit. So in that case should it light as its the first in the circuit?

 

[Steve]

Hey crafty I just tried to use my multimeter, set the switch to V~ 200, when I put the black probe to the neutral and the red to the live, there was a bang and I think ive blown a fuse at the CU.

should have had multimeter on a rating higher than 250V. having it on 200 would send the reading off the scale - it wouldn't give a reading, since UK electrics are approx 230v. Best bet is an autoranging multimeter. Where was the bang? hopefully it just blew a fuse inside the multimeter.

 

[ShaznMark]

The bang was at the multimeter probes, they are now black! Have the fuse working again now.I thought the multimeter should be set to A-(with £ dots)stands for DC i think, 10A. Its made by rapitest and has white and green sections.

What about the query on neutral?

 

[ShaznMark]

Okay got the multimeter working!Its showing 229/230 for all te live connectors, so as I was using the neutral on the black probe, does this mean everythings ok?!

Sorry, another question, what does continuity mean?

 

[Steve]

You were testing for voltage on current (A) setting? no wonder it went bang!

if its showing 230v between a live and that neutral then everythings hunky dory. screwdriver testers are unreliable. some stories indicate them lighting up when they aren't touching anything.

continuity . . . where you test for a continuous link - this test is used to show that you haven't got any broken wires in a ring main circuit, for example. It is also used in lighting to determine the switch cable.

To determine the switch cable, first turn the power OFF.
Set the multimeter to ohms, or the continuity setting if it has one (will bleep when there is continuity)
Test each twin and earth pair between red and black, while someone flicks the switch on and off.
When your multimeter goes beserk with bleeping on and off, you know you have the switch cable.

 

[ShaznMark]

...or if it showed up as 230v? Beginning to get it.
What would happen if you touched a live and a live with the red and black probes simultaneously? and also with neutral?

Can I use my multimeter to show deficiencies in my circuit?Like if I have too many spurs...my lighting circuit is more like aradial circuit at the moment. I will post a pic tonight if I get time.

 

[Steve]

lighting circuits are wired as radials. dont panic there isn't a lot of testing you can do to a lighting circuit with a multimeter. electricians have other test equipment such as insulation testers, earth loop impedance testers etc.

live to live on volts would probably give zero - it is measuring potential difference between them, so it is 0. Dont think it would blow up or anything.

 

[ShaznMark]

I will do out a drawing of the circuit and post it later, I really hate not being confident in what I am doing - Makes you feel like a fool!
Thanks for the help crafty!!!!!!

 

[Softus]

...or if it showed up as 230v? Beginning to get it.

Jesus H. Christ! Only now you're beginning to get it?!

Given your lack of knowledge and training on the subject of what you're attempting, the only valid advice to you is that you should engage a professional electrician.

 

[ShaznMark]

Hi softus, its only a small project I am attempting, and anything bigger I would definitely hire an electrician, however I would like to complete it myself and learn from any mistakes. I will then get my neighbourhood spark to inspect it and approve it. The internet is a great resource, you cant get feedback from a book.
mark

 

[Softus]

You can't get electrocuted by a book either

 

[ShaznMark]

Point taken softus...I can assure you I am a fast learner and even faster when my life is at stake!!I always switch off the relevant mcb when I am working on a circuit, and identify cabling properly, aswell as drawing diagrams for future reference. Asking questions is a good thing.