This is in my workshop which I built, and wired, about 30 years ago.
There are 12 fluorescent light fittings in 4 banks of 3. These controlled by
a 4 gang light switch.
This afternoon the lighting mcb has tripped twice for no obvious reason.
Never happened before. Power circuits unaffected.
Only change I have made recently is to change a tube and starter, 2 days
All lighting cables are 1.5mm surface mounted and 2.5 - 3.00 M above ground.
I have had a bit of a rodent problem recently but suspect that is not
I can't track the problem down as I cannot make it happen.
A bit worrying as I'm going away for a few days. The lights will not be left
Any thoughts please?
I do have an angle grinder and a multimeter.
Test it by running with half the lights on for a while:
1111 = trips
1100 = ?A
0110 = ?B
The results of A and B tells you which circuit is defective.
Then run with just that circuit hot and see if it trips.
It might be relevant but I don't see how.
It might be - they enjoy nibbling grey or black PVC for some reason.
While you are away isolate the faulty lighting circuit at the fuse box
or breaker just in case there is a charring rodent somewhere slowly
approaching red heat. A live to earth fault will trip the MCB but if the
critter is across live to neutral...
When i first had pet rats, i found out they absolutely loved eating the
scart cables linking the sky box to the tv in my bedroom, suddenly one
colour would disappear and the little bugger had got to the juicy copper
I asked the vet if there was anything i could put on the cables to deter her
from eating them, he said to try that bitter lemon stuff you use to stop
dogs licking their wounds,
Big mistake, that stuff was like a marinade to the rat, tho it did keep the
cables alive a little longer as she'd lick all the bitter lemon off before
devouring the actual cable,
Someone then suggested washing up liquid, nope, rats like that too it seems,
tho it did turn her turds green, and i am sure she farted bubbles for a
There is just something in the cable make up that is irresistible to rats
and mice, some say it's the electric current in the cable that attracts
them, but mine seem'd to prefer signal cables over mains cables....
Tho i will never forget when Nugget the rat chewed through the phone line to
the adsl box, we heard a squeak and the internet died, i looked behind the
sofa and watched him move a few inches up the cable he had just severed, and
in one snip he severed it again.... with the accompanied squeak as the cable
bit back, he sat and thought for a few moments, then moved double the
distance up the cable and 'snip - squeak' again,
i'm sure if i left him to it, he'd reach the socket, then start burrowing to
follow the cable back to the exchange.
Reminds me of this dilbert strip:
We used to have a lot of bother with underfloor high grade coax cables
getting eaten on low noise signal cables. They much prefered the cables
to the rodent bait and traps set to prevent them living in the void.
I don't think it is the mains they are after but something in the PVC
possibly the plasticiser. Usually when they bite though live they
promptly stop working and after a while start to smell bad.
Parrots amazingly can get away with it albeit with part of their beak
ablated by the flash as they cut clean through the "big worm".
Well I would suspect that there is nothing to worry about if the lights are
turned off. Probably a shagged ballast that will show up sooner or later.
Do the sensible thing and turn the power off to the lights at the CU whilst
you are away.
On Wednesday, April 30, 2014 7:59:15 PM UTC+1, Nick wrote:
You've most likely got an insulation problem from L to N or L to E somewhere. Things that could help narrow it down are:
- insulation test L+N to E
- insulation test L to N with all tubes removed
- disconnecting half the fittings (or some) and see if it still trips or not, repeat to narrow it down further each time
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