RCD tripping

[SoulkillaH]

Hi!

Yesterday i changed 2 heaters switchers and today the tenant called and told me he has no electricity on the sockets.

I found the RCD in the CU down.I tried few times to put it on but always is RCD tripped.

I changed the RCD with another one and the same thing happend.

After checking the connections of the heaters switchers which i installed one day before i start checking every MCB.

I found the problem on the bathroom lights switcher. Every time when i tried to switch the lights on ,the RCD tripped.

In the bathroom i have 8 spotlights,i checked every connections.

I took out all the bulbs and when i switch the light on the RCD did not trip.

I put a bulb back and again the RCD tripped.

Any sugestions?

 

[kme]

One of the lamps has blown; and is shorting; thereby tripping the RCD.

OR.

There is a further fault on the cable/fitting, causing a short when lamp is inserted.

Some test results would be useful, please?

 

[SoulkillaH]

There is a further fault on the cable/fitting, causing a short when lamp is inserted.

Some test results would be useful, please?

Without lamps the circuit looks ok.

But when i insert a lamp in one of those 8 sockets bulbs the fuse is tripping

 

[SoulkillaH]

I forget to specify, the RCD is protecting the ring circuit.when the RCD is tripping i have power in all lights circuits even in bathroom,i have power for shower and for heaters but not in the sockets.

 

[tom1]

One of the lamps has blown; and is shorting; thereby tripping the RCD.OR.

There is a further fault on the cable/fitting, causing a short when lamp is inserted.

Some test results would be useful, please?

if there was a prob with the cable would it not just constantly keep tripping,

if there was a probe with switch live would this also trip when switch is on reguardless of lamps in or out?

could the neutral be touching the metal light fitting?

 

[loonytoon]

Neutral to Earth fault on the downlights, thats why it only happens when the the lamps are in.

 

[tom1]

so the rcd trips but the lights stay on

borrowed neutral?

 

[SoulkillaH]

Neutral to Earth fault on the downlights, thats why it only happens when the the lamps are in.

Please can you be more specific?

and how this can be happens without any reason?

 

[SoulkillaH]

so the rcd trips but the lights stay onborrowed neutral?

no, the ligts are not on. But the tester it s shows i have live wire.

 

[tom1]

so the live is taken from the non rcd side of the board and the neutral from the rcd side

 

[loonytoon]

An RCD looks for an imbalance between L-E and N-E, in any combination. If the lights are on the same RCD, and the RCD only trips when you turn the lights on with the lamps in, there is a N-E Fault, as without the lamps in there is no current running down the neutral wire, and therefore, no imbalance. This may explain why it only trips with lamps in.

 

[bulmer]

An imbalance between Line and Neutral is what makes a RCD trip, as per when you get a fault to earth.

 

[loonytoon]

Fault to earth, thus causing an imbalance between either L or N. Hence the reason why when you turn an MCB off, removing L, then cut the cable, the RCD may/should in theory still trip. Hence the reason why care should be taken when working in sensitive areas such as offices etc, not to trip RCD when working on another circuit on same RCD.

 

[bulmer]

An RCD looks for an imbalance between L-E and N-E, in any combination. If the lights are on the same RCD, and the RCD only trips when you turn the lights on with the lamps in, there is a N-E Fault, as without the lamps in there is no current running down the neutral wire, and therefore, no imbalance. This may explain why it only trips with lamps in.

Where did you come up with this bit then?

 

[SoulkillaH]

so the live is taken from the non rcd side of the board and the neutral from the rcd side

yes,it looks in this way.

i understand the circuit lights can be wired through a RCD.Is this right?

 

[tom1]

yes,it looks in this way.i understand the circuit lights can be wired through a RCD.Is this right?

do u mean can the light circuit be on the rcd side?

yes it can but both live and neutral must be from the same rcd.

has the light mcb been moved from the rcd to the non rcd side

 

[SoulkillaH]

yes it can but both live and neutral must be from the same rcd.has the light mcb been moved from the rcd to the non rcd side

well, i didn t move anything,just i replaced the old rcd.

How can those lights were working yesterday and today are faulty?

what i am thinking to try is to borrow a neutral from another working light , to see if is working?It s this ok?

 

[loonytoon]

Where did you come up with this bit then?

Your not being very nice are you.

Ok, I'll admit it I got it wrong! Blushing

You are infact correct,

Under normal conditions the phase and neutral currents are equal and opposite so no flux is induced in the toroid and hence no current flows in the secondary winding.If an insulation fault occurs and current flows to earth, the phase and neutral currents will no longer be balanced.

Info HERE.

As the man in the orthorpedic shoes said, I stand corrected! :coat

Either way, he still has an N - E fault.

 

[loonytoon]

My quote didn't work! Oh well, you get the idea! LOL

*EDIT* Sorted!

 

[SoulkillaH]

Either way, he still has an N - E fault.

Btw, when i checked the connections i didn t see any Earth connection.