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DaveS

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Evening Chaps

On a job at moment and testing lighting circuits that have a lot of down lighters and a dimmer. Am I correct that if I disconnect live neutral and cpc from board join L-N together with all switches in closed position and test this to cpc and do IR test I have pretty much proved no short circuit between conductors including my switch lines. I will be testing initially at 250v as not to cause damage to dimmer and transformers. Thanks
 
As suggested in previous post the cpc needs to be connected to the means of earthing during an insulation resistance test, so don't disconnect from earthing terminal.
See guidance note 3.
 
Testing at 250 is only acceptable if electronic equipment cannot be reasonably disconnected but I would say in your case a dimmer is easily delt with and 500v can be used.
 
Testing at 250 is only acceptable if electronic equipment cannot be reasonably disconnected but I would say in your case a dimmer is easily delt with and 500v can be used.
The only time I use 250v is when filtered extension leads give false readings and I can't be bothered to unplug them otherwise, 500v all the time and thirty odd years on to my knowledge I have caused no damage.
 
Thanks all very much appreciated especially advice on leaving cpc in earth bar had never considered other cpc's could affect circuit. Always learning
 
The only time I use 250v is when filtered extension leads give false readings and I can't be bothered to unplug them otherwise, 500v all the time and thirty odd years on to my knowledge I have caused no damage.
An Older bloke I worked with used to damage smoke detectors all the time on a 500v test line -neutral.
Must have damaged about 5 houses worth till he realised o_O
 
Last edited:
Older bloke I used to work with used to damage smoke detectors all the time on a 500v test line -neutral.
Must have damaged about 5 houses worth till he realised o_O
Rarely test L/N on periodics unless 100% sure there is nothing across it so that will only be socket circuits
 
Is 500v not likely to damage transformers of down lighters? Also in this scenario for some silly reason all properties have been fed to switches so have atleast 5 neutrals and cpc's at back of box. I am trying to avoid as much any taking off and putting back of switch faces (which would have to do to bypass dimmer) incase I unintentionally cause conductors to become loose. This seems to be the sanest method so far
 
Rarely test L/N on periodics unless 100% sure there is nothing across it so that will only be socket circuits
Yeah we normally have an agreed limitation with clients in office eicr type premises.
No live - neutral IR testing on lighting circuits especially
 
Is 500v not likely to damage transformers of down lighters? Also in this scenario for some silly reason all properties have been fed to switches so have atleast 5 neutrals and cpc's at back of box. I am trying to avoid as much any taking off and putting back of switch faces (which would have to do to bypass dimmer) incase I unintentionally cause conductors to become loose. This seems to be the sanest method so far
Won't cause any damage what so ever.
 
I
Is 500v not likely to damage transformers of down lighters? Also in this scenario for some silly reason all properties have been fed to switches so have atleast 5 neutrals and cpc's at back of box. I am trying to avoid as much any taking off and putting back of switch faces (which would have to do to bypass dimmer) incase I unintentionally cause conductors to become loose. This seems to be the sanest method so far
its becoming common to take a mains down to switches with a neutral as it does away with needing unnecessary junction boxes above ceilings for things like downlights , makes it easier to terminate as well
 
Very true about logic of sometimes wiring to switches but here I really can't see what they was thinking it's a wooden plinth box cut into and can only get depth of shallow back box really with size of dimmer really is hard work getting all conductors at back of box
 
Very true about logic of sometimes wiring to switches but here I really can't see what they was thinking it's a wooden plinth box cut into and can only get depth of shallow back box really with size of dimmer really is hard work getting all conductors at back of box
Yeah 35mm or deeper is sometimes required especially if you've got an in and out mains and a switch wire.
 

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