Does this component exsist?

[yorkshire wizard]

Sorry all the work I do is industrial and many faults are in trunking were someone has added runs and circuits and danaged existing cabling?

 

[Hero999]

You're right that trunking can cause problems and cowboy work is an issue but can't that normally by found using visual inspection?

In my experience direct line to line faults are rare, earth to line is far more common and can be safely checked with 500V on any circuit.

It can still pass the insulation and conductivity tests but not pass the IEE, for example someone used too thinner cable or overfilled the trunking causing the existing cables to overheat.

 

[sheriff]

I think people are starting to understand the problem i am trying to overcome. I want to carry out the test without removing lamps or disconnecting anything. Becuse faults are more likely to occur when you are disconnecting and reconnecting cables. The 17th wiring regulations require you to test between L+N L+E and N+E. you can put a temporary link between L + N and then test them to earth to protect any sensitive equipment but this still involves adding and removing cables which is what i want to avoid. I want a double pole contactor that will only operate when more than 10mA is sent to it. Becuase my tester works at 500v and around 3mA.

 

[Hero999]

You don't have to always test all of the above, as I've said before, it's not always practical nor helpful. I think too many people blindly follow the book without actually thinking about what they're doing and why.

I would recommend omitting the L+N test, on circuits with sensitive electronics or devices which can interfere with the test, and just test L+N to earth, you can use 1000V if you like, anything should be able to stand up to that, otherwise it's not safe.

As I said before, it's extremely unlikely something is shorting from live to neutral because there's normally two pieces of insulation between the two line conductors and it would more than likely just blow a fuse if there was a short. Think about it, in order for the live to short to neutral, two piece of cable need to be damaged, two conductors need to have worked loose from the terminal blocks or a piece of swarf needs to be connecting two terminals in just the right place. Think about how unlikely this is. There's far more chance of either or both conductors coming into contact with the earth conductor than directly each other. The part of the circuit most vulnerable to a direct live to neutral short is inside the lamp ballast or an incandescent lamp itself which you don't even try to test because you can't do it.

Why are you doing the testing anyway?

Is it a new installation? If so the fittings shouldn't have bulbs in anyway.

If you're modifying an existing installation you only really need to test the modifications.

 

[yorkshire wizard]

The way i had done it was running a isolation circuit to operate a relay at each fitting but as I said there is a cost involved if i remember right one place would have to shutdown the 24/7 production line cover all machinary before anything could be touched above the machinery then when finished a hygine team had to clean all the machinary so it was worth adding the circuit ? the insurance compony stated that all tests must be carried out and no deviancec allowed on certs?

 

[Hero999]

It sounds like a waste of time to me.

People that just blindly follow the book like that are far more dangerous than those to actually think about what there doing.

The relays are just extra parts to fail with more connections that could potentially short out and will negate any supposed benefits of doing a silly test for the sake of the paperwork.

You might have known what you're doing but are you sure the person who came along later did?

I suppose if the results from an insulation test were 2M they would just blindly pass it because it exceeds thr 1M stated in the red book?

I wouldn't, I'd investigate the fault, a good installation should be >200M, and shouldn't even show up on the meter, it the resistance is 2M then you have a problem.