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Thread: Globes dont last long,suddenly pop.

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    Exclamation Globes dont last long,suddenly pop.

    Any brand or type of globes whether incandescent,CFL or LED sooner or later burst when switched on.This happens in a block of 21 flats only in two flats next door to each other.The other flats are not affected by this phenomenon.
    There is a three phase supply to the block of flats,triple pole surge arrestors have been installed after the incoming main switch.The neutral incomer has been earthed to the incoming earth of the supply cable which happens to be the armouring of the cable.Next I installed a mains filter on the lights circuit in the DB of flat 6 where the lounge pendant light was always the globe that violently shattered ,and now the second bedroom light is the one that pops.
    Perhaps someone reading this post has not only experienced this problem but has understood it and succesfully removed it.

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    Are the lamps that are blowing supplied via a dimmer? Are the two problem flats on a single or 3-phase supply? If single phase are both flats supplied by the same phase? If 3-phase, do the lighting circuits in both flats happen to be on the same phase?

    If I understand correctly you say you've connected the neutral and earth of the incoming supply....did you do this for the entire building or just for the two problem flats? Why did you do this? What was the earthing arrangement originally?

    I'd start by running a full test on the supply to both flats and a full visual inspection of all terminations paying particular attention for any evidence of arcing or overheating at termination points and obviously full tests of the lighting final circuits in the flats themselves also visually inspecting all connections at the accessories. Most of the cases of constant premature lamp failure I've seen are due to arcing caused by a poor connection somewhere, one was caused by arcing internally inside the switch which was old and had lost its snap action, I've also had burned neutrals in DB's cause lighting failures and worn/corroded lampholders can also give similar problems. I've also had one case where a neutral fault caused the phase voltage to rise in peak consumption periods and the lighting was the largest casualty.
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    Exclamation

    Thankyou Andy D for your reply.Both flats 5 and 6 are on the same single phase supply ,the block of flats were erected in the late 1960's,no dimmer modules are used in either of the two problem flats,B22 lampholders were replaced in both flats where the lamps were popping only resulting in flat 5 continuing to pop at the same light and flat 6 a different light started popping.
    Your suggestion of checking all connections from the DB through all switches and up to the light and plug points makes sense.The red conductors especially form a green oily paste due I'm told to a reaction between the pvc insulation and the copper conductor.Perhaps this paste is a factor in the problem as well as poor switch contacts and connections.
    The way forward clearly is a complete rewire together with circuit breakers, socket outlets,light swiches and lampholders.Once again Andy D I'm grateful for your advice.

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    Diamond Member AndyD's Avatar
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    The green goo as it's commonly known is a result of the plasticiser component of the PVC insulation leeching out and mixing with a small amount of copper oxide from the conductor. It's not really cause for alarm, on the few occasions I've encountered it the insulation integrity has always been very good and unless the PVC is showing signs of physical disintegration like cracking or splitting or extreme rigidity/inflexibility I wouldn't personally be in a rush to rewire, I'd probably just flag it as advisable for attention at some stage with the customer. I'd also doubt the goo is causing the lamp failures unless it's so bad it's gotten into the switch modules or lamp holders themselves.

    Obviously do tests first, incoming supply, impedance, IR etc and definately visually check all connections and terminations in the DB and along the circuits, that would be high on my suspect list. I'd be interested to know the global IR results for both flats ie whether the green goo is having any effect on insulation integrity. I'm also still interested what the original earthing arrangement of the installation was and where you made a N-E connection.
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