The importance of proving de-energised(isolated/dead) before starting work.

[marconi]

This is my first post as a new member. I am a stickler for safety, in particular proving wiring and terminals are dead before starting work. Here are two instances demonstrating the importance of proving isolation before touching any electrical conductors. I found them both in one flat I bought recently.

1. Economy 7 electric storage heating. The line supply for the electric timeswitch was from the Henley block via a separate stand-alone fuse way. The neutral supply for the timeswitch was obtained from the outgoing circuits neutral bar within the Wylex/MCBs CU supplying 3 storage heaters. I was replacing the dirty FCUs with new ones.

2. Two switched supplies to an outside light. A lantern type PIR outside light by the front door had two separately switched line feeds. There were 2 FCUs side by side at the top of stairs leading down to front door. The left FCU I first thought was solely for the door intercom transformer transformer just to its left: the right FCU I thought for the lantern PIR lamp. Both FCUs spurred from a socket on the other side of the stud wall. Whilst renewing the outside lantern and replacing old dirty FCUs I discovered:
a. Both FCUs were spurred from the socket.
b. The left FCU(3 Amp fuse) did supply the intercom transformer but also the line and neutral and CPC for the outside lantern.
c. The right FCU(5 Amp fuse) supplied a line to the external switch terminal (sometimes marked with a * on the connector) of the Lantern.

I am a strong advocate for turning off Main Switches, tripping RCDs, opening CBs and pulling out fuses and testing for dead before starting work. And once covers are off studying carefully how something has been wired and not assuming anything. These two instances make me glad I do what I preach.

Hope this little ditty is of interest and a reminder that electricity is a potential killer so take care.

PS: In a previous career, following the the death of a contractor from electrocution, I was appointed into to an industrial facility to re-introduce from scratch and then enforce safe systems of work for electricity.

 

[Darkwood]

Safe isolation
Testing
An understanding of circuits and the dangers associated with them, ie... borrowed neutrals been a very dangerous issue for any Electrician who is not aware of them.

We are taught to work safely and to take steps that power cannot be accidently re-established while the circuit is been worked on, this may be by another person or by a timer be it off peak supply or just general purpose timer, we are also taught that the public safety as well as our own must be taken into account too..

This thread although noting its a reminder is kind off teaching us to suck eggs and would be more suited to the DIY section where good advice like this may be taken on board by someone not as knowledgable as the professional members on here.

PS ... Welcome to the forum

 

[Marvo]

I think following proper lock-out procedures or complete disconnection. I've know a few guys who've been shocked accidentally by another guy they're working with be it an apprentice or a colleague sometimes it's poor communication but ultimately it's down to lockout procedures or lack thereof.

 

[baldsparkies]

I remember years back a qualified electrician liven a supply to a busbar with the cover still removed.
The apprentice with him reached forward as if to touch the bars and luckily he caught him out the corner of his eye and pushed him away before he made contact.
What the hell do you think your doing you idiot (he says)
Sorry !! the apprentice said.
They looked dusty I was just going to wipe it off.
This is a true story, and in my book it wasn't the apprentice who was the idiot.

 

[Darkwood]

I think following proper lock-out procedures or complete disconnection. I've know a few guys who've been shocked accidentally by another guy they're working with be it an apprentice or a colleague sometimes it's poor communication but ultimately it's down to lockout procedures or lack thereof.

My very first day with the company I worked for for 20yrs I was asked to cut a SWA and create a joint... straight forward , now this was the 80's so asked the boss if it was dead to which he said yes don't worry I wouldn't ask you to cut a live cable silly ........ BANG!!!! hacksaw blade blown to bits ..me in a daze and the boss redfaced full of lame excuses....

In reflection its the best thing that ever happened as it made sure I never trusted anyone else on my own safety be they the public or your own boss.... my mother wasn't impressed ....16yrs old - first day in job and I nearly got zapped lol

 

[Andy78]

I remember years back a qualified electrician liven a supply to a busbar with the cover still removed.
The apprentice with him reached forward as if to touch the bars and luckily he caught him out the corner of his eye and pushed him away before he made contact.
What the hell do you think your doing you idiot (he says)
Sorry !! the apprentice said.
They looked dusty I was just going to wipe it off.
This is a true story, and in my book it wasn't the apprentice who was the idiot.

Gives me shivers just to read that....

 

[Darkwood]

Gives me shivers just to read that....

Me too ... I always like my copper shiny!

 

[marconi]

Anecdotes likes these from professionals' own experience were how I/we attempted to create a culture of safety on the site I mentioned. They were much more effective than the 'tell' approach alone.

 

[ElectroChem]

Had a pointed lesson in this myself last week. Fault finding a heating coil, had turned off the manual heat and was in the middle of changing a relay when -SLAM- in pull the contactors from a timed function in the PLC.

Hands thrown up and stepped back. Five minutes to let the adrenaline fade and panel gets properly turned off this time. Could have been much worse if I'd had the tail in hand when it went live.

 

[Darkwood]

Had a pointed lesson in this myself last week. Fault finding a heating coil, had turned off the manual heat and was in the middle of changing a relay when -SLAM- in pull the contactors from a timed function in the PLC.

Hands thrown up and stepped back. Five minutes to let the adrenaline fade and panel gets properly turned off this time. Could have been much worse if I'd had the tail in hand when it went live.

Hmmm! ... not too sure what an apprentice Electrician is doing in the panel of a heating control system especially one thats live and PLC driven, I certainly needed several years to get my head around the various old and new set-ups in control panels to even warrant tackling them myself, unless this is what your company does and specialises in?.... my apprentice mishap was really a boss related issue and his fault but your delving into control kits that are plc operated and its possible removing the relay was the cause of the plc command to energise the contactor - - - you ever considered that you disconnected an input value from the PLC!

Its hard enough as a trainee to get the grasp of basic dangers in standard wiring systems but your entering into a whole different ballpark when accessing control systems....hopefully lesson learnt, plus I'd be questioning why your supervisor allowed you into such systems, maybe training differs down under but electricity still is just as dangerous; its just upside down there!

 

[ElectroChem]

Control systems are what our company specialises in but I was still complacent in not fully isolating the supply before changing the component. The initial fault was easily fixed, pop out a modular relay and replace. When I had the scare I was changing a solid state downstream of that relay.

The panel's control stream is an incredible kiludge. You've got a thermal controller switching 230V, driving a mini relay switching 24V, driving a 3ph SSR switching 230V for 3 of 4 elements, with one element's feed borrowed to drive another SSR for the 4th element!

 

[Geordie Spark]

Me too ... I always like my copper shiny!

Me too ...... it makes the spirit taste sooooo much better!!

https://www.youtube.com/watch?v=MLf1fDfSMN8 <<<<< --------- BEAUTIFUL voice!!

 

[baldsparkies]

Hmmm! ... not too sure what an apprentice Electrician is doing in the panel of a heating control system especially one thats live and PLC driven, I certainly needed several years to get my head around the various old and new set-ups in control panels to even warrant tackling them myself, unless this is what your company does and specialises in?.... my apprentice mishap was really a boss related issue and his fault but your delving into control kits that are plc operated and its possible removing the relay was the cause of the plc command to energise the contactor - - - you ever considered that you disconnected an input value from the PLC!

Its hard enough as a trainee to get the grasp of basic dangers in standard wiring systems but your entering into a whole different ballpark when accessing control systems....hopefully lesson learnt, plus I'd be questioning why your supervisor allowed you into such systems, maybe training differs down under but electricity still is just as dangerous; its just upside down there!

Possibly the companies NICEIC registered.
So the customer confidently uses them without checking out the man on the tools.
Happens all the time.
Qualified guys are busy earning the big bucks so send young Luke out.
He's a bright lad, doing well at college. Give him a bit of responsibility.
BANG !!
Seen it far to many times.
JIB card to all, and needs to be seen before commencing work.

 

[Deleted member 9648]

Had an interesting one last week where a specialist company came to a site where we carry out general maintenance. They were changing some equipment fed from an old panel and turned off the panel isolator and commenced work....BANG!
It turned out the panel isolator was defective...(there is another local isolator on the supply outside the panel). They are now threatening to sue the site because their man could have been killed. I suggested the site ask if they have ever heard of safe isolation proceedure as this is the first question H&S will ask.........it seems they've suddenly gone very quiet on the legal action front.

 

[baldsparkies]

Yep proving dead deffo comes to mind.

 

[Knobhead]

Possibly the companies NICEIC registered.
So the customer confidently uses them without checking out the man on the tools.
Happens all the time.
Qualified guys are busy earning the big bucks so send young Luke out.
He's a bright lad, doing well at college. Give him a bit of responsibility.
BANG !!
Seen it far to many times.
JIB card to all, and needs to be seen before commencing work.

What a load of bollox!

 

[Knobhead]

Had an interesting one last week where a specialist company came to a site where we carry out general maintenance. They were changing some equipment fed from an old panel and turned off the panel isolator and commenced work....BANG!
It turned out the panel isolator was defective...(there is another local isolator on the supply outside the panel). They are now threatening to sue the site because their man could have been killed. I suggested the site ask if they have ever heard of safe isolation proceedure as this is the first question H&S will ask.........it seems they've suddenly gone very quiet on the legal action front.

It may have gone quiet for a reason. Don’t think your isolation procedure covers every situation.

 

[Marvo]

I remember years back a qualified electrician liven a supply to a busbar with the cover still removed.
The apprentice with him reached forward as if to touch the bars and luckily he caught him out the corner of his eye and pushed him away before he made contact.
What the hell do you think your doing you idiot (he says)
Sorry !! the apprentice said.
They looked dusty I was just going to wipe it off.
This is a true story, and in my book it wasn't the apprentice who was the idiot.

Apprentices are scary things, I had a similar problem with one many years ago.

 

[trev]

Took my oldest lad on a job with me at a mates house when he was about 15, I knocked off the supply and told him to strip out a ceiling rose. I crept up behind him and just as he was about to put a driver on a terminal I screamed BANG. He very nearly fell off the ladder but after he'd gotten over the fright I explained safe isolation to him and why it's done the way it is.
He's never forgotten it.
I had the lesson taught to me in exactly the same way.

 

[Darkwood]

Had an interesting one last week where a specialist company came to a site where we carry out general maintenance. They were changing some equipment fed from an old panel and turned off the panel isolator and commenced work....BANG!
It turned out the panel isolator was defective...(there is another local isolator on the supply outside the panel). They are now threatening to sue the site because their man could have been killed. I suggested the site ask if they have ever heard of safe isolation proceedure as this is the first question H&S will ask.........it seems they've suddenly gone very quiet on the legal action front.

Depends here who had the responsibility of ensuring the equipment they were working on was dead, if it was themselves then the buck stop with them.

I had fitted a rotary Isolator so a compressor company could send his Engineer out to service the unit, I watched him switch off and lock off the isolator and that was it, before he touched anything I stopped him and did a dead test for him, he didn't grasp the dangers of his actions if the isolator failed etc... I contacted the company and expressed my concerns they also seemed too relaxed about it all but they did say it will be looked into.