There are live and exposed conductors in the back of a light switch. You may not be able to touch them with a bare finger but when you are poking a screw driver in you may come into contact with the terminals. Like I pointed out before, if you need to provide temporary lighting to cover the area when the lights are isolated then so be it, it isn't unrasonable in all circumstances to be dead if this can be done. "Work on or near live conductors" is only meant to be done as a last resort.
strange voltage reading
- Thread starter markymark2406
- Start date
so you would be willing to cover the expense of hiring in the temorary lights, the cost of time to set them up and remove them just for a 5 minute job?
do you also isolate every light switch and fused spur every time you take the covers off to do an earth loop test?
I'm not saying it's idiot proof, but the removal of a dead switch wire from a light switch by a competent electrician is hardly life threatening.. as long as he has insulated screwdrivers and a volt meter to check the wire is dead..
crabtree switches are more dangerous than some but MK grids are virtually impossible to get a finger anywhere near a live conductive part.
do you also isolate every light switch and fused spur every time you take the covers off to do an earth loop test?
I'm not saying it's idiot proof, but the removal of a dead switch wire from a light switch by a competent electrician is hardly life threatening.. as long as he has insulated screwdrivers and a volt meter to check the wire is dead..
crabtree switches are more dangerous than some but MK grids are virtually impossible to get a finger anywhere near a live conductive part.
We have to set up tempory lights whilst a lighting circuit is isolated. This is usually covered in part of the risk assessment.
A loop test is a live test conducted with approved test leads. This is only done when the circuit is complete, not poke a screwdriver about on the terminals and certainly not to work carry out work with the conductors on an accessory. Regulation 14 applies to this task.
You can still get a screwdriver in there tho.
I think it comes down to avoiding live working where ever possible but in a few circumstances live working may be absolutely necessary.
With the right knowledge, experience, tools and care live working can be safe.
With the right knowledge, experience, tools and care live working can be safe.
OK, time for a scenario.
As you know the circuit shares the same MCB as other lights.
Your task is to replace 2 luminaires. You have done the isolation by removing the wire from a switch as previously stated and re-energized the circuit. You remove the cover from the first fitting and have 2 phase wires, 2 neutral wires and 2 earth wires. The terminals in the fitting check out dead with approved testers.
How will you change the fitting and what are the risks involved?
As you know the circuit shares the same MCB as other lights.
Your task is to replace 2 luminaires. You have done the isolation by removing the wire from a switch as previously stated and re-energized the circuit. You remove the cover from the first fitting and have 2 phase wires, 2 neutral wires and 2 earth wires. The terminals in the fitting check out dead with approved testers.
How will you change the fitting and what are the risks involved?
again.. he says in the OP that he does it to prevent having to remove the breaker from the board.. which is absolutlely 100% unreasonable to isolate during normal working conditions in a hospital..
he also does not say that he worked live.. he doesn't mention that he turned the lights off either so unless he tells, we'll never know...
insulated screw drivers have between 5 and 10mm exposed depending on the size which, once inserted into the terminal screw hole would limit the posibility of contact with the live parts..
he also does not say that he worked live.. he doesn't mention that he turned the lights off either so unless he tells, we'll never know...
insulated screw drivers have between 5 and 10mm exposed depending on the size which, once inserted into the terminal screw hole would limit the posibility of contact with the live parts..
THIS IS NOT ADVICE TO DIY WORKING
DIY DO NOT WORK LIVE EVER
Person to watch me.
Three pieces of single terminal block.
Move the two phase to a piece of TB
Move the two neutral to a piece of TB
Ensure there is no way the fitting can become live from a damaged insulation on cable
Move the two earths to a piece of TB
If I was very paranoid about cables I might croc clip a temporary earth to the fitting.
Change the fitting
Put the earth back
Then neutral
and last the live......
DIY DO NOT WORK LIVE EVER
Person to watch me.
Three pieces of single terminal block.
Move the two phase to a piece of TB
Move the two neutral to a piece of TB
Ensure there is no way the fitting can become live from a damaged insulation on cable
Move the two earths to a piece of TB
If I was very paranoid about cables I might croc clip a temporary earth to the fitting.
Change the fitting
Put the earth back
Then neutral
and last the live......
i hadn't seen that scenario at the time of posting as i was still replying to your earlier post, I'm a slow typer..
there is the posibilithy that its 2 way and someone will turn the other switch on.. ( but this should have been addressed at the removal of switch wire stage.. )
there is the possibility of neutral feedback from other lights on the circuit.. ( but there's the posibility of that anyway even if you turn the breaker off.. )
there's the possibility that the neutrals to the rest of the lighting is fed through this fitting and breaking the neutral will take out the rest of the lights
oh and of course the old N-E slip of the cable that trips the rcd.. ( lights should not be on rcd's... and hospitals generally aren't.. )
in a hospital scenario, the lights are 99 percent of the time fed from removeable lighting connectors ( such as 'klik' roses.. ) so you'd just unplug them and change them..
there is the posibilithy that its 2 way and someone will turn the other switch on.. ( but this should have been addressed at the removal of switch wire stage.. )
there is the possibility of neutral feedback from other lights on the circuit.. ( but there's the posibility of that anyway even if you turn the breaker off.. )
there's the possibility that the neutrals to the rest of the lighting is fed through this fitting and breaking the neutral will take out the rest of the lights
oh and of course the old N-E slip of the cable that trips the rcd.. ( lights should not be on rcd's... and hospitals generally aren't.. )
in a hospital scenario, the lights are 99 percent of the time fed from removeable lighting connectors ( such as 'klik' roses.. ) so you'd just unplug them and change them..
Yep, there is the possibility of other lights on the same circuit upstream which can cause the potential on one of the neutrals to become live to mains potential when they are split. It shouldn't happen when the breaker is switched off as other lights along the circuit will also be isolated, providing the wiring etc is correct that is.
yes but in this scenario it's not reasonable to work live..
the removal of a switch wire from a switched off switch is reasonable to do..
but again the OP never said he did it live.. just that he removed it and when testing at the wall lights was getting a 50V reading..
the removal of a switch wire from a switched off switch is reasonable to do..
but again the OP never said he did it live.. just that he removed it and when testing at the wall lights was getting a 50V reading..
Yeah, but the wiring at a light switch is not a place to perform an isolation to work on the wiring. You need the whole circuit dead if you are replacing fittings etc. (unless as you said before they use the klik ones which would bear the question why he was inside the switch at all).
for all we know, there are no other lights on the circuit, he wanted to isolate the wall lights..
so removal of the switch wire isolates the wall lights from the feed rendering them safe to remove and terminate safely..
he just can't take the breaker out of the board or the wire out of the breaker without isolating the rest of the ward..
again, for all we know the breaker may still be off, but he's covering himself by removing the switch wire in case someone turns it back on at some point..
he's just wary that he's still reading 50v at the wall light..
so removal of the switch wire isolates the wall lights from the feed rendering them safe to remove and terminate safely..
he just can't take the breaker out of the board or the wire out of the breaker without isolating the rest of the ward..
again, for all we know the breaker may still be off, but he's covering himself by removing the switch wire in case someone turns it back on at some point..
he's just wary that he's still reading 50v at the wall light..
If it isn't feeding any other lights then what was the problem with doing a secure isolation at the board and not bothering with the switch? 
The original question was as you correctly say to ask about the 50v which was answered in the 2nd post. This brought on the question of his working practice which from the information given sounds like he was disconnecting the outgoing wire from a switch to minimise inconvenience to others, i.e. from having to kill the other lights on the same circuit. That is how I read the situation anyway. Only the OP can tell us more.
The original question was as you correctly say to ask about the 50v which was answered in the 2nd post. This brought on the question of his working practice which from the information given sounds like he was disconnecting the outgoing wire from a switch to minimise inconvenience to others, i.e. from having to kill the other lights on the same circuit. That is how I read the situation anyway. Only the OP can tell us more.
If it isn't feeding any other lights then what was the problem with doing a secure isolation at the board and not bothering with the switch?
I believe I already answered that question in the third line in my post above..
Me said:
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
