Electrician can't fix my tripping fuse

[mcrock]

We recently had extensive building work at our home which included replacing the fuse board. Since then, we've had problems with a couple of the circuits tripping. I've had the builder's electrician back a couple of times and he says he has extensively tested everything and replaced the breakers twice but the problem persists. It doesn't help that the problem doesn't happen when he's here so he's somewhat operating blind.

Before I insist on them providing a different electrician, or possibly forking out for one myself, I was hoping to get some pointers to encourage them to have one last try.

One of the problem circuits controls about 10 low-voltage lights, some of them dimmable. It may trip once a week or a couple of times a day and can do so when we're not actually turning anything on or off. Yesterday, it tripped (when almost all the lights were off) the second I turned the microwave on. The microwave is not even on the same circuit and continued to work. Also, I just noticed that when I manually switch off / on one particular different breaker, the problem one sometimes trips.

The problem breaker is marked "HAROK VKL003 B6 30mA"

Thanks very much for your help.

 

[londonboy]

Has the electrician given you your installation certificate yet?

I would be interested to see the Insulation Resistance results.

 

[mcrock]

wow - that was quick! I've got the certificate in front of me and am trying to work out what you need. Here are a couple of numbers, let me know if I've got the right ones:
Prospective fault current - 1.12kA
External earth fault loop impedance 0.17 ohms

 

[mcrock]

Actually, on a separate sheet it lists the Insulation Resistance for each circuit which is presumably what you're after. However, it doesn't show the problem circuit I was talking about, presumably because technically that circuit wasn't actually changed during the building work. It only covers the new circuits to the loft even though the whole fuse board was changed.

I do have an intermittent problem with the loft lighting circuit too. For this, the certificate shows figures of "200+" in each of the "Line/Neutral" "Line/Earth" and "Neutral/Earth" columns.

 

[Adam_151]

If the fuseboard was changed then there should be test results for each circuit reconnected to the new board (except for line/neutral, which is a risky test to do on an installation which may have hidden loads connected)

 

[holmslaw]

..

 

[nelectric]

It sounds to me like there may be some sort of N-E fault - I would be doing an insulation resistance test on the problem circuits, particularly checking N-E. And measuring earth leakage.

A Harok VKL003 is a RCBO, yet you say you have just had a new consumer unit fitted. I don't see why the electrician would have put the lights on a RCBO when the new board will have RCDs - unless he knew there was a problem with this circuit.

Contact the builder and explain you are still not satisfied and offer to give the original electrician one more chance to put things right. Tell him that if the electrician is unable to fix it then you will get another electrician in to fix it and expect the builder to cover the cost. That ought to at least get the builder to get another electrician in to give a second opinion.

 

[Monkeh]

A Harok VKL003 is a RCBO, yet you say you have just had a new consumer unit fitted. I don't see why the electrician would have put the lights on a RCBO when the new board will have RCDs - unless he knew there was a problem with this circuit.

Because using RCBOs is preferable to having the entire house on just a couple of RCDs? Boards don't have to come with them y'know.

 

[mcrock]

Thanks for all the advice so far. Armed with this, I'll have another go at getting the builder to address this.

 

[RF Lighting]

Sounds like he's not really an electrician.

Swapping the RCBO and hoping that cures the fault never works.

Swapping it twice is just clutching at straws from someone who doesn't really know what they are doing.

A proper electrican should be able to sort this for you.

A "harok" branded consumer unit doesn't exactly inspire confidence either.