electrical testing

[Sideways]

The fluke is one of the better non contact voltage detectors. It blinks slowly when powered on so at least you can tell that it's awake and not just sitting there with flat batteries. Great for finding breaks in electrical flex but as the earlier poster said, never trust one to tell you that a circuit is safe to touch.
A good digital meter is a versatile thing, but you need some knowledge to use them (don't go probing for voltage with the meter set to measure Amps or Ohms ...) and cheap meters can be so poorly made as to be dangerous.
Cheapest + safest overall is a two prod voltage indicator like Guineafowl suggested. KEW, Megger, Fluke, Martindale all make good ones. Steinel used to be the goto brand years ago. A basic model is enough.

 

[Sideways]

My knuckle touched one of the neutrals and I got a belt. Tested the neutral and it was live. So....your starter question for 10...how did that happen ?

You didn't do a safe isolation test before starting the job ...
Prove that your tester works
Check for voltage Live - Earth
Neutral to Earth
Live to Neutral
Prove that your tester is still working and hasn't failed part way through the test

But even this could be caught out if "everything" including the earth was live, or if there was a connection to a second source of power - like wiring connected between flats fed from different consumer units.

 

[bussy]

Should test at the service head for dead ie prove test lamps bottom of cutout to neutral, prove dead, top of cutout between neutral then earth and between neutral and earth, retest test lamps, bottom of cutout to neutral. If common neutral in meter cupboard possibly cross polarity in another flat back feeding through the neutral

 

[NetBlindPaul]

In the world of work, if you are doing anything with mainselectricity, a digital multimeter, or any tester which has a selection switch not considered suitable as a means of proving that something is dead.
The only approved tool is a 2 pole voltage indicator of the type shown in my friend JW’s youtube video linked above.

 

[Eric The Viking]

"Borrowed neutral", innit?

Was the hallway lighting (pick a common part of the property of your choice) actually wired across two consumer units - live from one, neutral from another?

 

[pe2dave]

In the world of work, if you are doing anything with mainselectricity, a digital multimeter, or any tester which has a selection switch not considered suitable as a means of proving that something is dead.
The only approved tool is a 2 pole voltage indicator of the type shown in my friend JW’s youtube video linked above.

Not considered suitable by who Paul?
Approved by who?

Avo 7 to modern DMM's, all meet the need if used appropriately.

 

[johnnyb]

Trust me. People can use anything that they want. I don't feel safe until my 2 prong says its dead. and I've checked its all working. often twice! mine has a check facility built in

 

[RichHox]

I've posted this before but worth repeating. Pre-Part P refurbishing a flat in London. Old school wiring, singles inside metal conduit. Replacing the consumer unit. Out to the upriser cupboard in the common parts landing and remove the fuse feeding the flat and take it with me. Lock the upriser cupboard door. Double-check no live - confirmed. Remove all wires from the old consumer unit and start to rewire in the new one.

My knuckle touched one of the neutrals and I got a belt. Tested the neutral and it was live. So....your starter question for 10...how did that happen ?

Might be the same as what Gazza said... Wired neutral into live/swapped at some point?

My thoughts on non-contact voltage testers - Absolutely brilliant thing to find a break in a cable but I gave up using them a while ago because they just dont seem to work reliably.

 

[Sandyn]

I normally use a DVM to check the wiring is dead, and I use insulated tools etc. but I don't trust anything, especially myself, so the last thing I do before I actually start working is to very quickly flick my finger across the copper.

 

[guineafowl21]

very quickly flick my finger across the copper.

I’ve heard of this being done by older electricians, and have done it once or twice myself. Probably not something to teach to the younger generation, though. Bear in mind that, especially if the circuit is not RCD protected, if you are leaning on an earthed metal piece at the time, you could easily get a fatal shock. If you must do it, put your other hand in your pocket.

There are stories of electricians being found sat on their toolboxes with a lit *** in their hands, stone dead. What seems to have happened is a hand-to-hand shock from working while leaning on the open metal door of the cabinet, followed by ventricular fibrillation (VF).

If you do get a belt, get into the habit of checking your pulse. If you are in VF, you won’t instantly die and there may be time to shout for help. In the case of the poor men above, they got the belt, felt woozy, sat down and lit a ***, and expired.

 

[RogerS]

Yup...a few of you have got it. The muppets who wired up the flats in the 1950's got two neutrals crossed over...ie I got one neutral wire from one of the flats and they had one of mine.

 

[Spectric]

Hi

Most places I have worked only allowed contact voltage testers with a proving unit, and this excluded DVM's which were not allowed to certify a circuit was electrically dead.

This Martindale product is good Martindale VIPD150 Safety Voltage and Proving Unit Kit

and these Kewtech units from Amazon.co.uk

 

[Phil Pascoe]

My friend, an electrician, told me he once got a bad kick from a three phase board - when he came around (flat on his back) he saw his footprints on the wall next to the board.

 

[Sandyn]

I’ve heard of this being done by older electricians, and have done it once or twice myself. Probably not something to teach to the younger generation

Absolutely! Not suggesting anyone should do this, just my final test and not a substitute for confirming the circuit is dead.
My reasoning being that I have confirmed the circuit is dead. I'm about to work on it and probably come in contact with wires, so there is no logical reason why I wouldn't do a limited touch contact first.

What I find very amusing is if you do go into VF after a shock. What do the medics do to you? Give you another shock....just to teach you a lesson...don't do it again!!

 

[Spectric]

Hi

Just 70mA can put you in your box.

 

[Rorschach]

My policy of trying to avoid touching wires (even if the circuit is dead) stood me in good stead when I changed a light fitting for my father. It was live all along. Since then I have also never trusted someone to tell me a circuit is dead.

 

[Sandyn]

Just 70mA can put you in your box.

probably less, According to my good old Product Safety guide, 60mA is the threshold for Non reversible heart failure and possibility of ventricular fibrillation, but you need contact for quite a while, but by 50mA, you are at the 'let go impossible' threshold, so higher probability of not being able to let go.
Even 10vrms can be fatal if you apply it to the right place in the right way.

 

[Gazzarose]

Yup...a few of you have got it. The muppets who wired up the flats in the 1950's got two neutrals crossed over...ie I got one neutral wire from one of the flats and they had one of mine.

Bugger me that's dodgy! Probably been happily working away like that for years. I wonder how that effected their meter readings!

 

[Spectric]

Hi

Yes there is a bit of a window, really depends upon the points of contact and the contact resistance but when I worked on boards or equipment I never had more than one hand in or near the equipment, having both as points of contact is really bad. Even worse is the plasma flash produced when high voltage boards fail, you lose skin, hair etc etc.

 

[Sandyn]

Here is an interesting graph. It's guide, not a standard. This is for duration of over 1S and for men. Women and children are more sensitive. For information only. Not for design use.