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Fluorescent strip light blows fuses when switched off, but not every time

Mm1

Dec 13, 2018
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Hello,
I’d be very grateful if someone could give advice on what might be happening and how to fix this.

When I turn off the ceiling flourescent strip light in the kitchen, it sometimes blows the light circuit fuses, but not every time.

The light fitting has a cylinder starter, and it comes on quickly without flickering. There’s usually another light on somewhere when this happens.

Thanks!
 

Tha fios agaibh

Aug 11, 2014
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When I turn off the ceiling flourescent strip light in the kitchen, it sometimes blows the light circuit fuses,
Strange, its usually when you turn on a fluorescent lamp when it blows a fuse.

Is this the household circuit fuse, or a supplemental fuse at the fixture before the ballast?
Have you verified it's the correct fuse?
 

Mm1

Dec 13, 2018
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Hi Tha,
Thanks for your response.
I think it must be the household circuit fuse because when I flip it back up, the kitchen strip light comes back on, along with any other ceiling lights that were also on in the other rooms).

By the supplementary fuse, do you mean the starter cylinder? I can’t see any other fuse...
I wonder if switching it off (via light switch on wall) causes some sort of surge in power in the tube which then trips the fuse?

I’ve just moved in to this old 1970's council flat and inherited the old lighting...mystery!
 
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Tha fios agaibh

Aug 11, 2014
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I think it must be the household circuit fuse because when I flip it back up, the kitchen strip light comes back on,..
You said "blows the light circuit fuses", but I believe you are referring to a tripped circuit breaker that can be reset by flipping its lever rather than a fuse that must be replaced when it blows.
I don't know where your located but is this by change a ground fault type breaker such as a gfci or Rcbo type breaker?
 

Tha fios agaibh

Aug 11, 2014
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Has someone recently worked on the wiring?
Is this a three way light switch that has two or more switches that control the same lights?
If your renting or leasing I'd tell the superintendent or landlord to call an electrician (at their expense).
 

Mm1

Dec 13, 2018
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Hi again,
I’m in London.
Yes sorry, it’s a circuit breaker but no idea which type (rather than a fuse that needs replacing).
Here’s a photo of it.
Yes, there has been a switch added (one labelled 'pump' in photo) by an electrician who was trying to get the shower extraction pump to do its job- should have been directly wired to the shower unit itself evidently!
A new boiler was fitted as well
The works done on the flat have been a catalogue of incompetent fiascos, with the exception of the boiler installation- I’ve just about lost the will to live!
I did get them to send an electrician yesterday about the light but because it’s intermittent he went away again, saying he might need to strip the whole wiring out.

Anyway, a friend suggested I replace the starter cylinder first, then the tube if it still trips.

Just tried to upload photo but no joy. The trip switches say ,'Crabtree RCCB' next to the lighting lever and also RCD PROTECTED CIRCUITS' next to levers for sockets and where the shower waste pump has been wired in.

Thanks again for your interest.
 

Tha fios agaibh

Aug 11, 2014
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The problem most likely is the neutral wiring from two or more circuits have all been tied together at some point along the wiring which causes a slight a current difference between the hot (brown) and neutral (blue) wires which is seen by your Rccb breaker as a ground fault. They are very sensitive to slight imbalances in current. A competent electrician should find this problem in short order.

I wouldn't bother with the starter or the lamps, not the problem.
 

Mm1

Dec 13, 2018
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Thanks so much - I’ll pass your advice on.
One last q - is it dangerous and a fire risk while in this state?
 

Tha fios agaibh

Aug 11, 2014
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Thanks so much - I’ll pass your advice on.
One last q - is it dangerous and a fire risk while in this state?
Obviously I can't answer specifically (ask an electrician) but breaker tripping is probably not anything to be worried about.
It only takes about 5ma of current for the breaker to trip and I believe its only seeing it for a fraction of a second when the light fixture discharges through the wiring when you turn it off.
Regards
 

Tha fios agaibh

Aug 11, 2014
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Most domestic units are 30mA.
Hospitals and the like are 10mA.
Not in America. I assumed ground fault protection levels were similar in UK. I figured the response was close enough to answer the op question.
Our Nec and UL stipulates ground fault protection for personal protection (class A) is to be between 3-6ma with most tripping with most manufactures having an imbalance trip of 5ma.
I
30ma seems high to me.

Now, why aren't my locations showing up with the little flag icon under people's names?
 

Bluejets

Oct 5, 2014
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30ma seems high to me.
You can look it up in the SAA wiring rules.

https://www.worksafe.qld.gov.au/for.../2017-bulletins/the-wiring-rules-are-changing

There are other associated requirements regarding trip time (for domestic) which is currently a maximum of 400mS although in my experience, most will trip somewhere between 10 and 40mS.
Testing 0 and 180 degree trips will show a slight difference also.

I'd be inclined to think the OP has a combination of circuits creating a cumulative effect due mostly to each having a slightly low test, which is a common occurrence and a good reason for multiple units.
 
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Tha fios agaibh

Aug 11, 2014
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You can look it up
I didn't say I don't believe you, it's just much higher than we're use to on this side of the ocean.
Your Au/Nz rules are a lot closer to UK codes than how we do things here, but if we're are all clear on design and terminology we can still arive with the same answers (regardless of location).

Had I saw the op location on my browser (they're not showing for me) I would have let someone more local answer it, particularly if specific codes are in question.
 
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