the importance of zones

[chris day]

Hello guys

something quite odd occurred , the job at hand had been to install a main bond to the gas pipe however on this occasion after checking the zones i saw no plausible reason for a cable to be in the location i had been about to drill.
i drilled a small pilot and during this i smelt carbon which immediately rang an alarm bell.
I check all sockets and the power was fine and no BS 3036 fuses has blown.
long story short i just about nicked a T&E cable which ran diagonal across the room, not an issue as i repaired the cable.
i checked the 3036 fuse and nothing had blown however quite a bit a black carbon i found whilst repairing the cable.
carried out all the tests and replaced fuse wire just in case, has anyone grazed a cable before and not blown the fuse? very strange as i ran a Zs off the circuit once repaired and all was fine on the earth fault loop.
The short had been between the line and earth

 

[westward10]

Did you create a short between line and earth.

 

[chris day]

Did you create a short between line and earth.

the short had been between the line and earth yes

 

[Wilko]

Late night musings ... is the polarity correct ? (is that fuse in the N and your L-E drill fault was never going to melt it...)

 

[chris day]

Late night musings ... is the polarity correct ? (is that fuse in the N and your L-E drill fault was never going to melt it...)

Yes Polarity was fine and check that during the repair.

 

[static zap]

What state was the drill bit in , blue hot spot , pited by a small arc ?
Cut and flung near mid-cycle...

 

[chris day]

What state was the drill bit in , blue hot spot , pited by a small arc ?
Cut and flung near mid-cycle...

A tiny tiny spot on the drill but nothing big and did not hear bangs or see any sparks

 

[static zap]

A tiny tiny spot on the drill but nothing big and did not hear bangs or see any sparks

Definitely a different outcome nails , or side-cutters !

 

[chris day]

Definitely a different outcome nails , or side-cutters !

I suspect being a dirty drill bit brushing the L and CpC this did not create enough fault
Current.
I have had similar sized arc damage during a Zs reading on a dirty bit of conduit in the past.

 

[static zap]

i smelt carbon which immediately rang an alarm bell.

A perfect example ,of using smell rather than touch luckily !
...in fault finding techniques .
Odds of doing it again .....

 

[chris day]

A perfect example ,of using smell rather than touch luckily !
...in fault finding techniques .
Odds of doing it again .....

Has anyone used cable tracers for walls, first time in 10 years catching a cable... are they any good?

 

[SparkyChick]

Has anyone used cable tracers for walls, first time in 10 years catching a cable... are they any good?

I've got a Bosch blue one, which is pretty good and seems to have a good depth of pickup. Results I would say are mixed in that it can, by virtue of being sensitive, lead you to being very cautious.

As an example, I used it when fitting some exterior lights. The house had recently been rendered, the cables for the lights had been fitted by another spark prior to rendering and my client didn't know where they ran so I had to be very careful fitting the lights. I spent an age trying to locate them because in some places it seemed to be picking up all sorts of metalwork making it very difficult. In the end I located the places with the weakest signal and took a punt.

Edit:- I should add, I didn't hit anything

 

[Wilko]

I have one, and unfortunately it's next to useless ... It will reliably find metal capping. But if Last Electrician has used metal capping, then it's probably in the right place so I don't need help to find it. Maybe expensive ones work better?

 

[Midwest]

I have a Bosch green one (diy version), and dependant on what day of the week it is and if there's an 'r' in the month, it will pick up the presence of metal or electrikery. The rest of the time it goes off at the merest hint of a piece of a wet lettuce.

The only remotest use for it I've found, is trying to trace the route of a cable. I'm led to believe if you pay for one of the very expensive professional versions (blue) they are more accurate (but not according to SC experience).

 

[Octopus]

My 3 top tips:

1. safe "zones" are a relatively new invention

2. Only sparks really understand them

3. Never assume cables run in zones, especially in older properties

 

[SparkyChick]

The only remotest use for it I've found, is trying to trace the route of a cable. I'm led to believe if you pay for one of the very expensive professional versions (blue) they are more accurate (but not according to SC experience).

In terms of finding stuff, it's fantastic, but I reckon it's probably capable of finding capping on the other side of the wall, so in that respect it's a little too sensitive. However, it does provide quite a bit of visual feedback which can be used to give you a hint. It has a couple of bar type items on the display IIRC that vary in size based on proximity. Sometimes it's a matter of getting them as small as possible rather than a green light.

 

[sparksburnout]

My 3 top tips:

1. safe "zones" are a relatively new invention

2. Only sparks really understand them

3. Never assume cables run in zones, especially in older properties

I used to give customers a printed diagram after larger jobs so they knew where the zones were, I thought it a good idea at the time. Then one bloke rang up saying he had put a nail through a cable in the other part of his house, and it was not in one of "my" zones, and it's all my fault so can I come and fix it FOC. I don't do it now.