electrical testing

[Jester129]

'Not for design use.'

LOVE IT!

 

[undergroundhunter]

Being a high voltage vehicle technician in my day job, when working inside the battery we have to 'gear up', insulated boots, 2 layers of gloves (one cotton, one insulated), overalls with a fine mesh inside to act as a faraday cage in the event of contact and a face shield. Of course these vehicles use dc and inside the battery there are no safety devices.

While training we were explicitly told that if we get a shock we should attend hospital as there is a risk of internal burns which in turn can cause an increased release of myglobin and platelets into the blood which can essentially poison you. This might not happen straight away but could be weeks later, they can test you blood and treat you accordingly.

Matt

 

[Chris70]

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.

I do that too, after using my Fluke. And then there are [Martindale] ‘Proving Units’ to consider.

 

[NetBlindPaul]

Not considered suitable by who Paul?
Approved by who?

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

Not considered suitable by the industry “voluntary regulatory bodies” such as the NICEIC, NAPIT, or the IET.
Not approved bu Her Majesties Health and Safety Executive.
No multimeter meets the need because it has the ability to be set incorrectly and then it would not indicate the presence or absence of voltage.
Look at the HSE website for the details.

 

[OldWood]

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.

I try to remember to use the back of the hand for this test as anything on the front is likely to make the hand muscles contract and therefore grip the cable. Ditto check the neutral too as that's the one that catches you out when it has gone live.

 

[Sandyn]

'Not for design use.'

LOVE IT!

lol, modern times! sigh!!

 

[pe2dave]

Not considered suitable by the industry “voluntary regulatory bodies” such as the NICEIC, NAPIT, or the IET.
Not approved bu Her Majesties Health and Safety Executive.
No multimeter meets the need because it has the ability to be set incorrectly and then it would not indicate the presence or absence of voltage.
Look at the HSE website for the details.

No current regulations then?
No specific current HSE directive Paul?
"Go look it up", sounds like you're quoting a doubting Thomas?

Were it so 'unsafe' I doubt they would be on sale in the UK.

 

[guineafowl21]

No current regulations then?
No specific current HSE directive Paul?
"Go look it up", sounds like you're quoting a doubting Thomas?

Were it so 'unsafe' I doubt they would be on sale in the UK.

What I think NBP means is that multimeters are not suitable for proving dead, according to the quoted bodies.

 

[AJB Temple]

I don't think multi testers or live current present devices are unsafe - but they can certainly be used in an unsafe way. I have a DMM that is Cat III, however, I use it so infrequently that I feel I could easily set it incorrectly and not realise until I get a belt.

I use the fluke testers as a belt and braces check, making sure they detect live, then doing a check on neutral, live, earth and casing before proceeding. This is after having checked with a two prong Mega that proves dead on the live wire.

I'm a bit paranoid. But for logical reason. Story time: several houses ago, pre Part P, I was doing some electrical work under the floor in a guest bathroom in a farmhouse we had. Largely new build, so nothing dodgy. The only other person in the house was a Philiipino midwife, Mary Lou, who we had hired as baby care support. Wife and baby were out. I turned off the circuit at the consumer board. Labelled it with a post it note (there was no lock) and explained to Mary Lou that the power was off and she must not touch it. I checked the circuit was dead and all was fine. About 15 minutes later I got a really big belt off the circuit. Fort reasons that I have never worked out, somehow Mary Lou misunderstood and she turned the power back on.

I was lucky and learnt a big lesson. Even since then I have made sure that consumer units in my house and workshops and outbuildings can be locked off with a padlock that only I have the key to.

 

[pe2dave]

I'm a bit paranoid. But for logical reason.

Large trim, but I agree. You and me both.
Once bitten (6kv in my case) n time shy?
Do whatever makes sure.
My cautious case, 220V but 600A. I asked for the board fuses. Asked the guy I was helping to touch everything (it was 120F and I was dripping).
Once sure, I helped him out, then handed back the fuses.
We do what we believe will not cause the pain of the last belt.

IMHO a lecky is a different beast to a home user checking the home system?
Used as per instructions, a DMM is 'safe'

 

[guineafowl21]

IMHO a lecky is a different beast to a home user checking the home system?
Used as per instructions, a DMM is 'safe'

Yes, as with many H&S type regs, you can do what you like in your own home - multimeter, light bulb with two wires, finger...

A sparky at work has to abide by the rules, and they consider a multimeter unsuitable for proving dead. Fine for diagnostic work, though, as long as it’s rated for the area you’re probing - Cat I-IV ratings.

 

[pe2dave]

A sparky at work has to abide by the rules, and they consider a multimeter unsuitable for proving dead. Fine for diagnostic work, though, as long as it’s rated for the area you’re probing - Cat I-IV ratings.

"They"?
Again, the mysterious they say...

 

[Spectric]

What I think NBP means is that multimeters are not suitable for proving dead, according to the quoted bodies.

That is absolutely correct, you must use the correct tester and confirm that tester is functioning first by using the proving unit, a multimeter or multifunction tester is classed as an instrument because it will have a calibration certificate. Things have really changed because I can remember when we just used a bulb tester or an apprentice. The procedure used now is to first prove live, then isolate and prove dead so as you confirm it is your action that resulted in the isolation. Reason being we used to just isolate and prove dead but I can remember a case where an isolation was performed and during the work one of the electricians got a kick and some burns as the power came back on. On investigation they had correctly isolated as per drawing but the drawing did not reflect the current system.

 

[guineafowl21]

"They"?
Again, the mysterious they say...

You’re certainly persistent...

HSE guidance on safe working practice (electrical work). Link here: https://www.hse.gov.uk/pubns/priced/hsg85.pdf

It’s on page 22, but I’ll quote:
“The use of multimeters, which can be set to the wrong function, is not recommended for proving dead on low-voltage systems, neither is the use of non-contact devices such as ‘volt sticks’’’

You might not be sent straight to prison for proving dead with a DVM, but if it’s at work and someone gets injured, HSE will look at your working practices and compare them to the guidance.

 

[CHJ]

Once when helping with the complete rewire of a large house in Malvern, the qualified (to local elec. company 11,000 volt line work) electrician and I checked that the 2nd. floor we were working on had been isolated by removing both live and neutral feeds from the dist. box and clamping them to earth followed by all rooms 3 pin round sockets L & N checked for no supply.

Slicing though the first lot of lead sheathed wiring with a Stanley knife saw the blade disappear in a spectacular shower of sparks, it turned out that another floors rising wiring had a live wire in contact with the lead sheath I had been cutting, and of course the lead sheath continuity proved to be none existent in many places.

 

[NetBlindPaul]

No current regulations then?
No specific current HSE directive Paul?
"Go look it up", sounds like you're quoting a doubting Thomas?

Were it so 'unsafe' I doubt they would be on sale in the UK.

Look at this guide from HSE:
Electricity at work: Safe working practices HSG85 (hse.gov.uk)
Then this one:
Electrical test equipment for use by electricians GS38 (hse.gov.uk)
Then refer to this:
ID3098_ ESR_Lock off infographic_040320.indd (electricalsafetyroundtable.co.uk)

Please do not show your ignorance and arrogance any further.
I know what is required by the NIECIE having been assessed by them as a competent operative, QS & PDH over many years before I transferred to NAPIT where again I was assessed and deemed competent.
If you are really interested in the ramifications of not undertaking safe isolation correctly then follow the path in my last linked document to Michaels story.
His sister Louise still gets upset telling it, I know, because I know her.

Nothing with a range selection is classed as acceptable for "proving" dead, these devices such as multimeters and multifunction testers have their use, but, they are not considered an acceptable method of testing for the presence of voltage when you are undertaking formal safe isolation.

I could start on the IEC definitions of voltage and illustrate that electric vehicles do not actually operate on High Voltage, but we'll park that for now.


This is what I do for a living BTW, I am also involved with the IET in regard publications related to BS 7671.

 

[OldWood]

Very many thanks for that , Paul - puts it all into perspective for all of us, particularly the routine for verifying isolation.

At the wrong end of 70 I am still learning!!
Rob

 

[RogerS]

Being a high voltage vehicle technician in my day job, when working inside the battery we have to 'gear up', insulated boots, 2 layers of gloves (one cotton, one insulated), overalls with a fine mesh inside to act as a faraday cage in the event of contact and a face shield. Of course these vehicles use dc and inside the battery there are no safety devices.

While training we were explicitly told that if we get a shock we should attend hospital as there is a risk of internal burns which in turn can cause an increased release of myglobin and platelets into the blood which can essentially poison you. This might not happen straight away but could be weeks later, they can test you blood and treat you accordingly.

Matt

Way, way back in time I was very junior and working on a BBC transmitter and working inside the guts of it standing on a ladder. I had very little clearance for my head where I was working. Unbeknownst to me, on one side the casing had, due to a fault plus poor DC isolation by me and my senior engineer before fault finding, become attached to the HT...a few KV. My ear touched. My head rebounded and hit the dead casing opposite which made me recoil to...touch the live again. I literally rattled my way downwards which probably saved my life. I kid you not.

 

[Sandyn]

My ear touched. My head rebounded and hit the dead casing opposite which made me recoil to...touch the live again. I literally rattled my way downwards which probably saved my life. I kid you not.

Have you thought of starting a circus act??

 

[Eric The Viking]

I never worked in Transmitter Group but I did visit some.

I'll never forget being shown the inside of the old long wave (Light Programme (Radio 2) then Radio 4) transmitter at Droitwich - 1/2 MW at the final output stage (just disappearing up a wire)... This was in the days when it was valves: they were about a foot tall and water cooled, which was weird enough (tens of thousands of volts 'twixt top and bottom of the valve), but there was so much current too that you could actually see the electron beam down through the valve. The mercury arc rectifiers were also impressive - there were viewing ports into them, so you could see the arcs, and they looked like they came from Frankenstein's lab...

In case anyone is interested (reading the link below, I probably saw the 1963 configuration):
https://www.bbceng.info/Operations/transmitter_ops/Reminiscences/Droitwich/droitwich_calling.htm