180v between live/neutral but 240 between live/earth

[kev.k]

Hi all

Downstairs lighting circuit isn’t working so tested voltage at each fitting and getting 180 live-neutral and 240 live-earth. Have checked continuity from board to each fitting and got a neutral all the way around the circuit so I’m a bit stumped on what the issue can be.

There is access from the board to under the floor boards upstairs so I can pull a new twin from the board and re wire the lights without any disruption or damage if I have to but hoping for an easier fix.

Any ideas?

 

[Julie.]

Just do a R1 - R2 and a Rn - R1 loop test, I would think that you somehow have two lamps in series, or a very bad contact somewhere

 

[PEG]

Hi,where are you measuring this 180v? Which live,and which neutral?

 

[kev.k]

Hi,where are you measuring this 180v? Which live,and which neutral?

Hi, getting 180v at every fitting. Had a look for joint box somewhere under floor boards but can’t see any

 

[snowhead]

You say you have a Neutral all the way around but in reality you haven't.

It's most likely a bad connection on the Neutral.

Have you tested L - N at a fitting with the light switched ON?

Have you tested L - N at the Consumer unit on the Lighting cct?

You may have 180v L - N on the meter but it's probably breaking down under load.

 

[James]

Results speak for themselves, obviously there is a high resistance in the N between the supply and the fitting.

Poor connection
Broken cable
Mouse problems
Incorrectly wired light fitting?

First look for a shiny new B & Q style light fitting somewhere
After that it is a logical fault finding approach, find the broken N.

 

[kev.k]

Thanks for the help guys!

There was an old JB between the leg from board to the first light and was missing a screw from one of the terminals so someone had used insulation tape to connect the neutrals together which had eventually come undone. WOW! The neutrals were still barely touching, hence the continuity of the neutrals all the way around but obviously not enough to be carrying the current.

Thanks again

 

[7029 dave]

Classic signs of a broken neutral/ HR , glad you sorted it.

 

[telectrix]

Thanks for the help guys!

There was an old JB between the leg from board to the first light and was missing a screw from one of the terminals so someone had used insulation tape to connect the neutrals together which had eventually come undone. WOW! The neutrals were still barely touching, hence the continuity of the neutrals all the way around but obviously not enough to be carrying the current.

Thanks again

thanks for letting us know, and welldone for finding the fault.