help.. insulation test problems..intermittent fault

[vitoboy]

yeh..
..ta

 

[vitoboy]

there are no problems
only the nic

 

[vitoboy]

no capping dot and dab

 

[telectrix]

if it werew a medical problem, you'd get a second opinion. sometimes a second mind on the problem spots in seconds what the first has missed.

 

[vitoboy]

thats why im here.............

 

[SPARTYKUS]

my money's on a nicked cable from the patress screws, or a screw happy spread (but its dot and dab so maybe no screws?).

Chippy use a nailgun? They're great aren't they

Hope you find it vitoboy

 

[vitoboy]

maybe i will just askmy nic inspector when he turns up
but i guess he might go with the....get the hammer out...ha
i wil sort it tomorrow and post after
do or...........well . . do really init

 

[robskiing]

Im going to ask the obvious neutrals and earth completely disconnected from DB is there a fused spur with a neon connected giving you a reading . If not any of the previous suggestions sounds like a trapped cable pressure fault good luck

 

[dsb electrical]

hi i am wondering if you have disconected the mentioned rcbo unit whilst under ins res. test as it would pick up a neutral and earth path thro the functional earth wire and neutral .

 

[vitoboy]

dot and dab so no screws
all cables L N E disconnected from the db (either in connectors or ends sperated depending on test)
no spurs no neons nothing but sockets

ok today ill load up the circuit...as a radial...nice long radial...put some big load on the far end and see if i can make it worse.

problem is that the house is finished any cable repacement will require holes in the sub floor and plaster removed from walls.
if i cant show that its a certian fault (ie it just dissapears)then ill be left carrying the cost of all that !

its for a family friend to so no pressure init.

 

[vitoboy]

today i got it sorted.
i turned the ring into a radial(one side in connectors at the c/u
fitted a 32A mcb instead of a rcbo.
pluged in a kettle..dehumdifyer..and the bar fan heater.
for about an hour the clamp meter said about 25 amps (apart from refilling the kettles)
after this my n e fault was there as before.all ends seperated at the db.
i split the ring at a thrid and ir tested back to the db...clear
tested the other way...fault...
so went to the next socket removed it and tested back toward the previous one..fault
so i have 1 bit of wire between two sockets thats n/e fault .63 M ohms.
so i pulled out one end of it with a new one on the end...right up to where it goes down the wall into the dot and dab to the socket.
tested the same bit of wire after pulling it out....nothing...clear >299.....
ive striped the bit i pulled out..all good no damage
ive ir tested it all clear.
ive ir tested the bit thats left behind the dot and dab all clear.
where did my fault go.
was it the hot cable after loading it..?
what was it...?

ta all

vitoboy

 

[vitoboy]

900jim
makes me wonder about cable quality..this stuff was from a good wholesaler..bs marked and all...but how can my fault be anything but the quality of the cable?
ie at places in the cable the insulation is to thin...the wire is not in the center of the insulation??
any ideas on this anyone

 

[tony mc]

Apparently there is alot of copy cable out there Wiring matters have had a article on it in the past.

Had a simular fault the other day but it turned out to be a damp piece of plaster lying on top of the cables entering the back of the socket. Low IR between CPC N & L.

 

[gpz900jim]

Its a shame that after all of that you couldnt positively say whats wrong, at least that would have given you some peace of mind. As I said previously, not long ago, I had the same problem. The bad reading kept coming and going and when its like that, its impossible to pin it down. It really is odd.