Arcing on cu cover screws

[FCC5206]

Hello all

I have replaced an old rewireable fuseboard an noticed arching on the screws that secure the lid. Obviously it is a metal box. Any ideas what could cause it to arc at this point!!
all the tests were ok although the IR readings were low as it's an old place. Just wondered what u thought!
thanks in advance

 

[Pete999]

Hello all

I have replaced an old rewireable fuseboard an noticed arching on the screws that secure the lid. Obviously it is a metal box. Any ideas what could cause it to arc at this point!!
all the tests were ok although the IR readings were low as it's an old place. Just wondered what u thought!
thanks in advance

How low were the IR reading?

 

[FCC5206]

How low were the IR reading?

The lowest was on a ring at 68. It is a rental property so looks like a historic fault but I've never seen scorch marks there so was wondering what might have caused it.

 

[Pete999]

The lowest was on a ring at 68. It is a rental property so looks like a historic fault but I've never seen scorch marks there so was wondering what might have caused it.

Sorry to be flippant 68 what?

 

[Deleted member 26818]

Did you see sparks, or are you referring to black around the screw holes?

 

[FCC5206]

Sorry 68Mohms L&N to earth as lots of inaccessible appliances

 

[FCC5206]

Just blackening round the screw holes

 

[Pete999]

Sorry 68Mohms L&N to earth as lots of inaccessible appliances

That's a global IR test is it? What was the test voltage?

 

[FCC5206]

No I tested every circuit that was the lowest reading. On the kitchen ring. There was also heaps of blackening around the fuses on 2 of the lighting circuits but nothing unusual there!!

 

[FCC5206]

Oh and at 500v

 

[Pete999]

No I tested every circuit that was the lowest reading. On the kitchen ring. There was also heaps of blackening around the fuses on 2 of the lighting circuits but nothing unusual there!!

Rewire able fuses?

 

[FCC5206]

Yep BS3036

 

[Deleted member 26818]

I doubt that the black is evidence of arcing.
More likely due to heat escaping through the screw holes.

 

[FCC5206]

Ahh nice thank you makes sense with a large pop in the fuse!!

 

[Octopus]

Maybe on your next CU change you should do an IR reading on each circuit. I always do.

As for relying on L&N to E - I simply don't accept that there were appliances on every circuit.

 

[FCC5206]

Maybe on your next CU change you should do an IR reading on each circuit. I always do.

As for relying on L&N to E - I simply don't accept that there were appliances on every circuit.

Sorry please read one of my earlier post i did do an IR on every circuit this was the lowest reading on the kitchen ring.
For info i have never done a global IR as it never gives satisfactory results.
But in this case I was never going to move a full American style fridge freezer!! :0)

thank you

 

[PEG]

Only a minor point,but on old,fixed units,such as this,don't underestimate 40+ years of draughts,staining gaps in this manner. I have seen markings that look identical to scorching etc,but were quite obviously decades of dust/fumes/soot.If both unscrewed OK,this is most likely.:conehead:

 

[telectrix]

agree with peg. it's probably just muck.