I was testing the thermostat

[1stfix2ndfix]

and it was in a bit of a tight space the crocodile clip had lost it's grip a bit and kept slipping of the earth terminal so I was really trying to force it on. When I went and put the live and neutral probes on to the live and neutral (in) of the switch it went bang!
Obviously I've learnt a lesson here that if the crocodile clip is touching the earth and the live? and you put the probes on it goes bang. The thing is I'm not sure what really happened and why

 

[telectrix]

sounds like you put them on live and switch live perhaps.

 

[davesparks]

Right, what exactly went bang? What test were you trying to carry out?

 

[telectrix]

IR test om imm. heater with the power still on?

 

[davesparks]

No, he said he was using 3 test leads.

The imm heater makes sense though, I've been trying to work out how a roomstat has ended up in an awkward place to test it!

But if it is an immersion heater why on earth wasn't it switched off whilst the probes were attached and then switched on?

 

[7029 dave]

As above what test was you attempting?.

 

[terminator]

I presume that you're an apprentice and learning the trade? If so why weren't you shown how to carry out the test that you were doing? If you were unsure, why didn't you ask your supervisor.

What test were you trying to carry out? Why were you doing live testing without supervision?

 

[jaypp]

As above, very vague info. Are you sure it was an earth as plumbers are known to use cpc as another conductor if they need one and still use g/y sleeving if sleeved at all!!!

 

[Octopus]

Safe isolation anyone?

 

[1stfix2ndfix]

I'm at work ATM but will reply tonight with a bit more info.

 

[1stfix2ndfix]

I've got a quick ten mins

yes I'm working as an electricians mate. I don't want to ask him to many questions as I don't wanna slow him down and loose me job.

But he did say I must of had the crocodile clip touching the earth and live terminals.

it was a earth fault loop impedance test so it was live, yes it was a immersion heater and I tested it at the switch. Once I had secured the earth to the earth bar only or at least that is what I thought! And then put the probes on. One on live the other on neutral (supply side) I saw a big blue flash and then some black smoke. It also went bang. I'd like to know what happened and why it happened if anyone can help It would be appreciated

 

[telectrix]

had you got meter set to continuity by mistake?

 

[Deleted member 72666]

Two things! 1/ Have you got your eyesight back?
2/ Does your meter still work or have you hidden it?

 

[Jay Sparks]

You may have inadvertently touched the back box with the probe also in the live terminal, especially if there wasn't alot of room.



Jay

 

[plugsandsparks]

Same thing happened to a lad I was showing how to test ELI on the back of a FSU. I said "Whatever you do, don't short mi probes by catching them across live and earth. " Sure enough he took a chunk out of my probe.... and it did make a nice bang. It happens... So if there is a chunk out of it and everything still works... there you go, if not I have no idea.

 

[1stfix2ndfix]

No as there quite old testers. I think what has happened is that as I've put the crocodile clip on the earth and then twisted the switch to put the live and neutral probes on I must have knocked the clip so it came into contact with the live and that's when it went boom. I'm not sure why this happened as in it went boom but someone might be able to explain why? If it was live and neutral I've been told it would go bang to but if it was neutral and earth it wouldn't.

 

[1stfix2ndfix]

Yes the switch was fine a bit black from the soot but it all worked ok. The testers were fine as well they still worked as we've used em today. There bloddy old though. Instead of it being a multi function one we've got 3 seperate ones.

 

[telectrix]

that's so that you can only bugger them up 1 at a time . :24:

 

[Richard Burns]

If the meter is still working and the switch is still working then the likely explanation is that your probe / crocodile clip came into contact with two conductors and shorted out the circuit, either between line and neutral or between line and earth.
The high flow of short circuit current will cause the bang and the smoke and the soot ( and presumably a couple of melt points on the probe!).

 

[1stfix2ndfix]

Thanks for all the replies very helpful