Insulation Resistance - Live to Neutral short

[Newbie90]

Hi all,

Just a quickie. I carried out an insulation resistance test on a lighting circuit which only has two rooms consisting of 4 lights.

Live to earth and neutral to earth was fine but when I tested live to neutral I got a short circuit.

All the bulbs were removed so just wondering if anyone had any ideas?

The Zs reading was 0.73 ohms.

Thanks

 

[Plonker 3]

Insulation of cable had deteriorated?

 

[Bobster]

Not got switches with a neon in them? Is this domestic?

 

[Jay Sparks]

Smoke detectors wired from lighting circuit??? Another load connected somewhere, maybe in loft???

 

[KAS1]

Could be a fault !!!!!!!!!

 

[Plonker 3]

Could be a fault !!!!!!!!!

No that never happens, must be something else causing it too happen.

 

[KAS1]

needs investigating

 

[KAS1]

Method statement to fault find. No 1 put safe isolation in place

 

[Marvo]

If this was an existing circuit and it wasn't tripping or blowing fuses before you arrived then there's some kind of load still connected to it. Check the L-N resistance with a normal multimeter and try figure out what is connected and where.

 

[Deleted member 9648]

Hi all,

Just a quickie. I carried out an insulation resistance test on a lighting circuit which only has two rooms consisting of 4 lights.

Live to earth and neutral to earth was fine but when I tested live to neutral I got a short circuit.

All the bulbs were removed so just wondering if anyone had any ideas?

The Zs reading was 0.73 ohms.

Thanks

Two possibilities-:

1.Something still connected which may or may not now be fried....(tv booster in loft....loft light)?
2. A fault.

 

[Newbie90]

There are no neons on the switches.

There is a tv amp in the attic, would that be spurred from lighting by any chance?

 

[trev]

Crikey.

 

[Newbie90]

Two possibilities-:

1.Something still connected which may or may not now be fried....(tv booster in loft....loft light)?
2. A fault.

Just replied at same time, I'm thinking tv booster

 

[Deleted member 9648]

Two possibilities-:

1.Something still connected which may or may not now be fried....(tv booster in loft....loft light)?
2. A fault.

There are no neons on the switches.

There is a tv amp in the attic, would that be spurred from lighting by any chance?

Yep.....possibly.Hopefully it's survived 500v up it's essentials.

 

[Plonker 3]

There are no neons on the switches.

There is a tv amp in the attic, would that be spurred from lighting by any chance?

did you not think to test to see if that was connected to the circuit?

 

[trev]

There are no neons on the switches.

There is a tv amp in the attic, would that be spurred from lighting by any chance?

They often are, try unplugging it and retesting. If it clears then there's your problem, hopefully you won't have fried it. This is an example of why it's wise to do a test on 250v before the proper one at 500, they don't like it up em

 

[moose]

Four lights not transformers in circuit is there, spot lights ? this may be it ?

 

[Sintra]

For all it takes its wise to do a quick continuity test between L & N before applying 500V.

Edit. Or as Trev states IR test at 250V

 

[Octopus]

biting my lip!

 

[yellowvanman]

measure on your low resistance setting to see if its a dead short or not - more than likely something connected - aerial booster?

 

[Newbie90]

I'm pretty sure it's the tv booster!

Will check it out tomorrow as its a property I have just purchased to rent out. Therefore, no rush whilst its unoccupied.

Cheers for all the advice

 

[Jimmyb]

dimmer switch

airel booster

 

[Octopus]

I'm pretty sure it's the tv booster!

Will check it out tomorrow as its a property I have just purchased to rent out. Therefore, no rush whilst its unoccupied.

Cheers for all the advice

You may need to buy yourself a new amp

Every day is a learning day - but I really don't know what possesses people to do a 500V IR test on a system which they are not 100% familiar with

 

[telectrix]

if they're short try pulling a bit of slack through. :75:

 

[Plonker 3]

You may need to buy yourself a new amp

Every day is a learning day - but I really don't know what possesses people to do a 500V IR test on a system which they are not 100% familiar with

I struggle to understand why people have test equipment when they can't understand test results it gives them.

 

[Steve_P]

Hi all,

Just a quickie. I carried out an insulation resistance test on a lighting circuit which only has two rooms consisting of 4 lights.

Live to earth and neutral to earth was fine but when I tested live to neutral I got a short circuit.

All the bulbs were removed so just wondering if anyone had any ideas?

The Zs reading was 0.73 ohms.

Thanks

It's those daffodils you're using in the lighting circuits mate.

 

[Deleted member 9648]

I struggle to understand why people have test equipment when they can't understand test results it gives them.

Well he understood it wasn't right....just didnt know what was causing it to be not right and had the gumption to ask....better than a bang test I suppose.

 

[HandySparks]

Crikey.

Straight out of the Beano, Trev. Funny how one word can make you smile.

And a damn sight more effective than a heap of sarcasm and abuse.

 

[electricpawn]

if there was a short circuit between a phase conductor and neutral...either a protective device should have tripped or operated ...or you would have had something go...BANG !!!

 

[Octopus]

Hum, according to the OP's other thread on a similar subject he had isolated everything and had >299 IR on all cores!

 

[guest119]

Dimmer switch????????????????? (what is that all about)

Its the bell transformer.

Boydy