Testing whether a mains cable is live

[onedsla]

Hello,
Hoping to run something by those more familiar with home electrics.

I'm doing some basic troubleshooting on a couple of issues in my new house.

In the first case, after routing through several outhouses (where the electrics work), a cable then leads to the garage (where they do not). I'd like to establish to which point electricity is flowing to identify what's broken.

The second is to double check that a particular circuit is off prior to replacing a flood light.

Would something as simple as the below give me a simple 'yes or no' answer, or do I need to invest in something more fancy?

http://www.screwfix.com/p/forge-steel-mains-tester...

[Rickyy]

Get yourself a multimeter and read up on some safe electrical isolation procedures.

It's surprisingly easy to get a shock from what you may think is a dead cable!

[FlossyThePig]

I use a phase tester all the time and check both "live" and "neutral" cables to make sure the power is off to the circuit I am going to work on. I usually turn off all power of with the master switch rather than individual circuits at the fuse board.

Many years ago I lived in a house where the fuses had been wired into the neutral side of the supply. Fortunately a "sparky" friend sorted that out as there are some jobs I will not tackle.

[auto1]

onedsla said:

Hello,
Hoping to run something by those more familiar with home electrics.

I'm doing some basic troubleshooting on a couple of issues in my new house.

In the first case, after routing through several outhouses (where the electrics work), a cable then leads to the garage (where they do not). I'd like to establish to which point electricity is flowing to identify what's broken.

The second is to double check that a particular circuit is off prior to replacing a flood light.

Would something as simple as the below give me a simple 'yes or no' answer, or do I need to invest in something more fancy?

http://www.screwfix.com/p/forge-steel-mains-tester...

Trust my life to device worth £1.79 inc Vat .
Let me think about that a moment.

[auto1]

FlossyThePig said:

I use a phase tester all the time and check both "live" and "neutral" cables to make sure the power is off to the circuit I am going to work on. I usually turn off all power of with the master switch rather than individual circuits at the fuse board.

Many years ago I lived in a house where the fuses had been wired into the neutral side of the supply. Fortunately a "sparky" friend sorted that out as there are some jobs I will not tackle.

So maybe best to check live to earth, as well then.

http://www.esc.org.uk/fileadmin/user_upload/docume...

Edited by auto1 on Wednesday 15th January 14:42

[onedsla]

auto1 said:

So maybe best to check live to earth, as well then.

http://www.esc.org.uk/fileadmin/user_upload/docume...

Thanks all - so a voltage indicator multimeter looks like a more suitable tool for the task.

[JimbobVFR]

Rickyy said:

Get yourself a multimeter and read up on some safe electrical isolation procedures.

It's surprisingly easy to get a shock from what you may think is a dead cable!

I wouldn't use a multimeter for this under any circumstances. Its really easy to have it set to the wrong function and just a bad idea.

Those crappy neon screwdrivers are very handy and I have one myself. I use it for mixing epoxy resin glue :-)

I use something similar to this http://www.tester.co.uk/metrel-tek900-led-voltage-...

ALWAYS prove the unit is working before AND after using it.

[Ganglandboss]

onedsla said:

Hello,
Hoping to run something by those more familiar with home electrics.

I'm doing some basic troubleshooting on a couple of issues in my new house.

In the first case, after routing through several outhouses (where the electrics work), a cable then leads to the garage (where they do not). I'd like to establish to which point electricity is flowing to identify what's broken.

The second is to double check that a particular circuit is off prior to replacing a flood light.

Would something as simple as the below give me a simple 'yes or no' answer, or do I need to invest in something more fancy?

http://www.screwfix.com/p/forge-steel-mains-tester...

Those are excellent for jemmying lids off smaller paint tins; as a reliable test instrument they are useless. The only thing you should ever trust is a proper test lamp with two probes - never trust anything with a single contact or a device that you wave near the cable. Multimeters will do the job, but I prefer to use a test lamp:

http://www.amazon.co.uk/Fluke-T90-Voltage-Continui...

• They do not need a battery to function
• The leads are protected by a fuse or current limiting device
• They do not rely on the user to ensure the leads are in the correct socket or the correct range is selected

When isolating, test the power while it's live and check your instrument detects a voltage. Test between live and earth, live and neutral, and neutral and earth. Find the fuse or MCB and isolate (if you can turn the lot off at the main switch, even better). Test again - if it's off, test your instrument again on a known supply to prove it is still working. If in doubt, get a spark in.

[mrmr96]

JimbobVFR said:

Rickyy said:

Get yourself a multimeter and read up on some safe electrical isolation procedures.

It's surprisingly easy to get a shock from what you may think is a dead cable!

I wouldn't use a multimeter for this under any circumstances. Its really easy to have it set to the wrong function and just a bad idea.

Those crappy neon screwdrivers are very handy and I have one myself. I use it for mixing epoxy resin glue :-)

I use something similar to this http://www.tester.co.uk/metrel-tek900-led-voltage-...

ALWAYS prove the unit is working before AND after using it.

I actually think that the glowing screwdriver is more suitable for this task. It's quick and easy to use, no chance of wrong setting and no chance of being electrocuted by it. (If you connect a multimeter probe to a live cable then remember that the other end of the multimeter cable will also be live. If it came out of the meter, of you fingers got near it you could get a shock. This £2 device is insulated except for the tip which you touch to the cable, and the top which you touch your finger on to earth it. They've been around for years and are reliable IME.

[mattdaniels]

auto1 said:

Trust my life to device worth £1.79 inc Vat .
Let me think about that a moment.

Stupid statement is stupid.

[Ganglandboss]

mrmr96 said:

JimbobVFR said:

Rickyy said:

Get yourself a multimeter and read up on some safe electrical isolation procedures.

It's surprisingly easy to get a shock from what you may think is a dead cable!

I wouldn't use a multimeter for this under any circumstances. Its really easy to have it set to the wrong function and just a bad idea.

Those crappy neon screwdrivers are very handy and I have one myself. I use it for mixing epoxy resin glue :-)

I use something similar to this http://www.tester.co.uk/metrel-tek900-led-voltage-...

ALWAYS prove the unit is working before AND after using it.

I actually think that the glowing screwdriver is more suitable for this task. It's quick and easy to use, no chance of wrong setting and no chance of being electrocuted by it. (If you connect a multimeter probe to a live cable then remember that the other end of the multimeter cable will also be live. If it came out of the meter, of you fingers got near it you could get a shock. This £2 device is insulated except for the tip which you touch to the cable, and the top which you touch your finger on to earth it. They've been around for years and are reliable IME.

Have you any electrical training? Any time served spark will tell you neon testers belong in the bin. The device in the link is not a multimeter - it is an approved test lamp as recommended by the HSE. It does not have removable leads and does not have to be switched on or to a particular range.

[grumbledoak]

If it's your day job you should get more and better, but the crappy screwdriver is a decent double-check. Just don't take all your clothes off and get in a bath full of water before you touch the wire!

[mrmr96]

Ganglandboss said:

mrmr96 said:

JimbobVFR said:

Rickyy said:

Get yourself a multimeter and read up on some safe electrical isolation procedures.

It's surprisingly easy to get a shock from what you may think is a dead cable!

I wouldn't use a multimeter for this under any circumstances. Its really easy to have it set to the wrong function and just a bad idea.

Those crappy neon screwdrivers are very handy and I have one myself. I use it for mixing epoxy resin glue :-)

I use something similar to this http://www.tester.co.uk/metrel-tek900-led-voltage-...

ALWAYS prove the unit is working before AND after using it.

I actually think that the glowing screwdriver is more suitable for this task. It's quick and easy to use, no chance of wrong setting and no chance of being electrocuted by it. (If you connect a multimeter probe to a live cable then remember that the other end of the multimeter cable will also be live. If it came out of the meter, of you fingers got near it you could get a shock. This £2 device is insulated except for the tip which you touch to the cable, and the top which you touch your finger on to earth it. They've been around for years and are reliable IME.

Have you any electrical training? Any time served spark will tell you neon testers belong in the bin. The device in the link is not a multimeter - it is an approved test lamp as recommended by the HSE. It does not have removable leads and does not have to be switched on or to a particular range.

Sorry, my opening sentence shoudl have said "I think a glowing screwdriver is more suitable than a multimeter". I was agreeing with the guy I quoted.

[eldar]

Check with the back of your hand, never the palm!

[Rickyy]

mrmr96 said:

Ganglandboss said:

mrmr96 said:

JimbobVFR said:

Rickyy said:

Get yourself a multimeter and read up on some safe electrical isolation procedures.

It's surprisingly easy to get a shock from what you may think is a dead cable!

I wouldn't use a multimeter for this under any circumstances. Its really easy to have it set to the wrong function and just a bad idea.

Those crappy neon screwdrivers are very handy and I have one myself. I use it for mixing epoxy resin glue :-)

I use something similar to this http://www.tester.co.uk/metrel-tek900-led-voltage-...

ALWAYS prove the unit is working before AND after using it.

I actually think that the glowing screwdriver is more suitable for this task. It's quick and easy to use, no chance of wrong setting and no chance of being electrocuted by it. (If you connect a multimeter probe to a live cable then remember that the other end of the multimeter cable will also be live. If it came out of the meter, of you fingers got near it you could get a shock. This £2 device is insulated except for the tip which you touch to the cable, and the top which you touch your finger on to earth it. They've been around for years and are reliable IME.

Have you any electrical training? Any time served spark will tell you neon testers belong in the bin. The device in the link is not a multimeter - it is an approved test lamp as recommended by the HSE. It does not have removable leads and does not have to be switched on or to a particular range.

Sorry, my opening sentence shoudl have said "I think a glowing screwdriver is more suitable than a multimeter". I was agreeing with the guy I quoted.

Well looks like I've been told!

I'd still use a multimeter over a neon screwdriver! All of the ones I've had (even cheap ones) have had recessed connectors at the meter end, so you'd have to be pretty unlucky for it to pull out and then touch the connector!

Of course you could hurt yourself if you'd set it incorrectly, but you shouldn't really be using one unless you are competent anyway!

The thing I don't like about the screwdrivers is the only light up between a certain range, so a live cable, which appears to be dead, could infact be live! (albeit at a low voltage)

[v12bitch]

if its a single supply then easy enough to test, you need to make sure the feed is not on a timed breaker or from another switched circuit that may show no potential at one time and change potential at another time. if a pair of cables are there things can become more involved, wont confuse the issue but shock from a neutral is poss and very dangerous should you become part of the circuit . have seen people simply touch all the wires together and see if it flashes or trips a breaker NOT RECOMMENDED pm me if you want a step by step done my apprenticeship 1970 lol from a 1.5v batt to over 33kv stay safe

[Ganglandboss]

mrmr96 said:

Ganglandboss said:

mrmr96 said:

JimbobVFR said:

Rickyy said:

Get yourself a multimeter and read up on some safe electrical isolation procedures.

It's surprisingly easy to get a shock from what you may think is a dead cable!

I wouldn't use a multimeter for this under any circumstances. Its really easy to have it set to the wrong function and just a bad idea.

Those crappy neon screwdrivers are very handy and I have one myself. I use it for mixing epoxy resin glue :-)

I use something similar to this http://www.tester.co.uk/metrel-tek900-led-voltage-...

ALWAYS prove the unit is working before AND after using it.

I actually think that the glowing screwdriver is more suitable for this task. It's quick and easy to use, no chance of wrong setting and no chance of being electrocuted by it. (If you connect a multimeter probe to a live cable then remember that the other end of the multimeter cable will also be live. If it came out of the meter, of you fingers got near it you could get a shock. This £2 device is insulated except for the tip which you touch to the cable, and the top which you touch your finger on to earth it. They've been around for years and are reliable IME.

Have you any electrical training? Any time served spark will tell you neon testers belong in the bin. The device in the link is not a multimeter - it is an approved test lamp as recommended by the HSE. It does not have removable leads and does not have to be switched on or to a particular range.

Sorry, my opening sentence shoudl have said "I think a glowing screwdriver is more suitable than a multimeter". I was agreeing with the guy I quoted.

I disagree with that too. Your points about multimeters are valid but I still prefer them over neon screwdrivers. The main danger with a neon is it only has a single point of contact and relies on your body to complete the circuit. If this reference to earth is poor, it may not indicate. In order of preference:

1) HSE GS38 approved test lamp
2) Multimeter with fused and double insulated test leads
3) That's it!

[Brother D]

So what is the consensus on the best tool? I've always used a multimeter in the past for testing (live-neutral, live-earth, neutral-earth).

Speaking of testing... I have inherited an alarm panel - and when switched on shows an alert for 'earth fault'.

It powers two zones of smoke detectors @ around 67V, and bit of testing shows the fault is with one of the zones with about 10 smoke detectors. Simple testing is not showing any continuity between live/neutral & earth. The cables are all buried, so any suggestions on how one would find an earth fault? Or is it a case of getting a spark in with specialised equipment to locate rather than chasing out all the walls/ceilings.

Out of interest, as all the smoke detectors and panel are made of plastic etc, is an earth legally required for the LV side? - and if so, what is the cutoff when an LV circuit requires an earth?

[v12bitch]

Brother D said:

So what is the consensus on the best tool? I've always used a multimeter in the past for testing (live-neutral, live-earth, neutral-earth).

Speaking of testing... I have inherited an alarm panel - and when switched on shows an alert for 'earth fault'.

It powers two zones of smoke detectors @ around 67V, and bit of testing shows the fault is with one of the zones with about 10 smoke detectors. Simple testing is not showing any continuity between live/neutral & earth. The cables are all buried, so any suggestions on how one would find an earth fault? Or is it a case of getting a spark in with specialised equipment to locate rather than chasing out all the walls/ceilings.

Out of interest, as all the smoke detectors and panel are made of plastic etc, is an earth legally required for the LV side? - and if so, what is the cutoff when an LV circuit requires an earth? its not always a voltage cut off point but the way the item is made, all plastic needs no earth some plastic with some metal may also not need earth if double insulated. all these item will have codes or a logo displayed an earth fault under ground could be a joint with damp getting in electrical issues are not east to find by chatting, hands on teating is required, as a pointer tho if you have 10 on a circuit, split the cicuit or remove a detector at a time fault finding can be a pain sometimes

[Alucidnation]

FFS.......

OP, just get a local registered sparky to check it for you as it wont take long to check by someone who knows what they are doing.

At lease that way, a)you will still be alive and b) he can safely isolate it or recommend what would need doing etc.

If you dont want to do that, use one of these...


http://www.screwfix.com/p/kewtech-kt1780-s-ac-dc-v...

There are slightly cheaper ones around but i figured there must be one of these stores near you.