Time to get the megger out!

[Nocker]

Had a problem on a workshop lighting circuit at my new firm. I am the only electrician there so i can't bounce off anyone.

The circuit is fed from a 32 way square D consumer unit and has roughly 10/12 double fluorescent tube fittings on the 10a type C breaker.

The breaker is is feeding a one way switch which operates the lights.

Breaker will switch on okay until a load is put on the circuit by operating the one way switch and then will not reset.

I have so far disconnected every tube and starter from each fitting and i am still getting the breaker tripping with everything removed.

I have only ever tested domestic circuits before so i would just like to ask anyone who can help is the process the same on a 32 way just testing 1 circuit?

Also if anyone could think from previous experience what kind of problem could be causing this?

Also would the ballast in each fitting need to be disconnected before pumping 500 meg through them.

I can see myself full of dust, ****e and ceiling tiles in my eyeballs tomorrow.

Oh the joys!

 

[gnselectricals]

I would say a faulty ballast, gotta open them all up, usually find scorch marks indicating the faulty one if not time to start testing
Regards Graeme


Sent from my iPhone using Tapatalk

 

[cogsey133]

Agreed sounds like a faulty ballast. I would tend to go to the mid point and split the circuit thus trying to cut down the area involved.

 

[mackers]

prob be a faulty ballast! fault finding is fault finding domestic or commercial both same . break down circuit etc you maybe able to find it by smelling the fittings lol a burnt out ballast has quite a disstictive smell! let us know how u get on!
sounds like a 3 ph db so be careful 400v is not very forgiving!lol

 

[telectrix]

check in each fitting that cables have not been run internally, alongside the ballast. have seen a few burnt cables from this.

 

[Guitarist]

Does indeed sound like a burnt out ballast, but don't dismiss the fact that it could be a damaged cable inside the conduit. May be worth sticking your nose against each unit, you may get lucky and smell the unit with the faulty ballast.

 

[jay sean]

Does indeed sound like a burnt out ballast, but don't dismiss the fact that it could be a damaged cable inside the conduit. May be worth sticking your nose against each unit, you may get lucky and smell the unit with the faulty ballast.

+1 for this

 

[imago]

As already sid, but I would add two things.

1) Before sniffing around make sure the ceiling tiles and pipe lagging etc aren't asbestos.
2) Before sniffing light fittings make sure no one else is around. Otherwise you'll look a right berk.

 

[jay sean]

you might look like a berk, but if you do your job properly, and get the lights working they will be very happy !!!

 

[jumpin jax]

In the op it is stated that the mcb trips with everything disconnected so why would it be a ballast? My money would be on an accessory screw piercing insulation or as said in a previous post cables in conduit rubbing on a fitting. Has anyone done any electrical work in the route of the cables.

No-one wouild see him sniffing, its dark!!

 

[mackers]

have a read again every lamp and starter disconnected!

 

[Guitarist]

In the op it is stated that the mcb trips with everything disconnected so why would it be a ballast? My money would be on an accessory screw piercing insulation or as said in a previous post cables in conduit rubbing on a fitting. Has anyone done any electrical work in the route of the cables.

No-one wouild see him sniffing, its dark!!

As mackers says, he has only removed tubes and starter, not delved into the guts of each unit

 

[cogsey133]

Breaker will switch on okay until a load is put on the circuit by operating the one way switch and then will not reset.

I have so far disconnected every tube and starter from each fitting and i am still getting the breaker tripping with everything removed

if you remove the tubes and starters then all that is left is the wiring or the ballast. The supply to the fitting goes to the ballast first so there could still be a faulty ballast causing a short. The wiring may also be the problem.

 

[jumpin jax]

iI stand corrected, :dunce:

 

[Guest111]

prob be a faulty ballast! fault finding is fault finding domestic or commercial both same . break down circuit etc you maybe able to find it by smelling the fittings lol a burnt out ballast has quite a disstictive smell! let us know how u get on!
sounds like a 3 ph db so be careful 400v is not very forgiving!lol

Your right it aint very forgiving but it aint half good at removing eyebrows when it goes wrong,as i know from experience lol.