Bang! Large flash / bang at voltmeter tips.

[mechelec]

We have all done somthing similar at some point. The important thing is to learn from it. Saying that most people have probably done it more than once. lol

 

[Dazza1976]

I must admit, i have done this myself before, so i will be careful in future.

Just to add though, someone mentioned about stripping back the cable and putting in a connector block before testing to see if its live or not, but you wouldnt want to go stripping back cable and terminating until you know that it is dead, hence the reason he probably tested that way in the first place, so what would you suggest ? use a volt stick ? As you cant assume a cable is dead just because everything is switched off at the board ?

 

[rmc86uk]

Agreed with above. How can you isolate the circuit if you do not know what the circuit is hence why you are testing for voltage in the first place.

Sent from my HTC Desire using Tapatalk

 

[rryles]

Switch off at main supply and then test with voltstick? (Oh and still assume it could be live!)

 

[sparky3366]

In the late 80's, a college tech in the electrical department somehow managed to blow the blue phase on the main busbar on the incomer. Turns out he went over red & blue phases with a little multi-meter. All the college had to be sent home...
This is the same college where a lecturer insisted on calling ohms 'barrats' as in barrat homes cos he thought it was funny. One guy failed his 236 because he kept putting barrats in his exam paper instead of ohms.
The same lecturer was sacked for an issue of ordering cable & fittings from the wholesaler and ending up with washers, kettles etc instead, which he promptly sold on...alledgedly

 

[ian.settle1]

Switch off at main supply and then test with voltstick? (Oh and still assume it could be live!)

In the immortal words of John McEnroe


You can not be serious!

 

[rryles]

I was completely serious. This was as a precursor to stripping the offending cable and terminating into a terminal block so that you can then correctly identify and isolate.

What else would you suggest? Test the cut end of the cable with probes? Isn't that where the OPs original problem started?

 

[Dazza1976]

Switch off at main supply and then test with voltstick? (Oh and still assume it could be live!)

Im not sure if he was actually saying do this, or if he was questioning my previous post, i think there may be some misunderstanding.

In my post i was asking how you would test if a cable like this was live, as previous posts suggested stripping back the cable and terminating in a connector block to test, but i pointed out that you wouldnt really want to do it this way if the cable is live, thats why i asked about using a volt stick, coz i know of a time where my ex college mate got a nasty bolt, where he went to work on a circuit, the main switch on the consumer unit was off, but it turned out there was another small 1 way consumer unit that was hidden.

 

[Dazza1976]

Sorry just read your reply rryles, and i do agree with what you are saying, it will be interesting to hear what the others say on this matter.

 

[ian.settle1]

For one a voltstick in the eyes of the HSE is not an approved voltage indicator.

 

[Dazza1976]

Yes fully agree Ian, but how else would you go about testing if it is live ?

He used an approved voltage indicator in the first instance, and that is what caused his flash bang !

In the safe isolation procedures, once you have isolated the circuit to be worked on, you need to test it to see if it is dead, if you cant use an approved voltage tester because of the risk of shorting out, and you cant use a volt stick because they arent approved, then What would be the correct procedure to test it safely ?

Lol, this has the makings of one of those great posts that will be argued about for weeks !

 

[rryles]

Exactly the point I was trying to make Dazza.

The situation is a piece of T+E, that has a cut end. You don't know where it is supplied from or of it is already dead. What do you do?

My suggestion, but I'd welcome others thoughts was:

switch off & lock off main switch
Test tails with volt stick to prove it.
Test mystery cable with volt stick, to confirm it is dead (probably).
Test tails with volt stick again to prove it.
Strip cable and terminate into terminal block, being as careful as possible in case it is actually live still.
Switch back on and main switch.
Use approved voltage indicator to check if cable is live and if it is then identify and isolate as per normal safe isolation procedure.

It's not ideal to be using a volt stick, but it's the best I can think of.

By the way - I routinely use a volt stick, but only as a "second opinion", after using an approved voltage indicator and proving unit.

 

[telectrix]

totally agree there. if you can't safely connect an " approved " tester to the conductors, a volt stick (and care ) is the only way.

 

[malcolmsanford]

Good procedure except you should prove the voltstick works first

Welcome to the real world of electricians, there is not one among us that as not had a flash bang or wallop and no matter how it shakes us I bet it will not be the last.

I can see where Ian is coming from, but perhaps the voltstick is the safest way you can deal with this.

Though There are others ways perhaps not so safe ................................

 

[telectrix]

dab it on a known earth. not only will that show that it'e live, also doubles as a fuse finder.

 

[RogertheBodger]

In extreme cases snip a bit off the end, Carry an old pair of insulated pliers for this reason, don,t forget to avert eyes!

 

[telectrix]

In extreme cases snip a bit off the end, Carry an old pair of insulated pliers for this reason, don,t forget to avert eyes!

don't be a wimp. strip it with your teeth.

 

[RogertheBodger]

don't be a wimp. strip it with your teeth.

Ouch, what a mental picture that is......

 

[Lofty]

I actuallay saw someone do that with a piece of 2 core flex when I was an apprentice. It was the 'norm' for this guy to strip the tails with his teeth only this time he did it on the 'load; end of the mains flex which was still plugged in. it was in a workshop, on the bench and all supplies were from an isolating tx. But it still carbonated ?? the inside of his mouth and funnily enough it was the last time he did it. The guy by the way had been in the trade at that point for over 20 years, with that sort of practice I'm surprised that he managed that long !!.

Cheers,
Lofty.

 

[Marvo]

......in future to isolate all the power if necessary, strip the cable back and put it in a connector block so you can then identify the circuit.........

.......Just to add though, someone mentioned about stripping back the cable and putting in a connector block before testing to see if its live or not, but you wouldnt want to go stripping back cable and terminating until you know that it is dead,.......use a volt stick ?.......

It was probably me that started the minor 'voltstick' riot but I did say 'isolate all the power if necessary' before you strip back the cable to put it in a con block.

I wouldn't bother with the voltstick if the CU was isolated I would just use old sidecutters and 1KV rated insulated gloves and goggles. There's also a little trick you can use with flat twin type cables where you make a very short cut into each side of the cable about an inch along from each other. You cut deep enough to nick the conductors which will then break by gently bending the cable side to side. Once broken you can pull the insulation a little and expose the earth enough to cut it. It's also best to do a few practice runs first on scrap cable and also use old side-cutters, gloves and glasses and I would only do it with smaller cables such as lighting circuits.