quick test on a garage

[chris gray]

its a sub board fed from the house, how many sockets are there on the circuit?
the comment i made about the 250v test was as hed said hed done it n-e
'l-n at 250v for proving purposes is valid'

 

[WayneL]

Some dodgy replies to this thread, chaps - you all been on the cider??

hi its tn-s in the house, no the cables were not discotted at the garage cu didnt realise you had to do that, what are your thoughts on the R1+R2 thanks again

Tnc-s supply 6mm armour out to feed main board in garage

It's one or the other????

you did disconnect the cables for the test didn't you?

An IR Test - Why

If you tested the distribution board/installation as a whole then you need to disconnect the neutral/earth link for a TN system.

What neutral/earth link?

The live neutral fault could be due to the main switch not being open. If this is the case, then you would be seeing the neutral-earth link the PME head if it's TN-C-S, or back at the star point of the transformer if it's TN-S.

On an IR test?

thanks for all the replys so basically what i should have done was disconnected the ring from the board and then done the insulation tests?

No! No! No!

as for the insulation resistance, if you are testing 1 circuit only, you must disconnect it, (L,N+E) and of course disconnect/unplug any appliances and remove any bulbs etc,

Really?? GN3 page.....?

Oh dear - if he wasn't confused before, he will be now

 

[Risteard]

What neutral/earth link?

Neutral and earth are connected whether at the cutout in the consumer's installation or at the earthed neutral of the supply company's windings.

 

[WayneL]

Neutral and earth are connected whether at the cutout in the consumer's installation or at the earthed neutral of the supply company's windings.

Has no bearing whatsoever on your IR test as the main switch should be open, anyway, isolating the neutral.

It only matters in a three phase board, where the three phases are isolated, but the neutral isn't.

 

[Johno]

whisky actually, what don't you agree with

 

[WayneL]

whisky actually, what don't you agree with

Disconnecting conductors at CU for IR tests - & why?

 

[Johno]

because if they were still connected (depending on a few things) it would make a difference to the readings

 

[Risteard]

Has no bearing whatsoever on your IR test as the main switch should be open, anyway, isolating the neutral.

It only matters in a three phase board, where the three phases are isolated, but the neutral isn't.

Indeed. For some reason I was thinking of a three phase board which clearly isn't relevant to this situation. You're right - I must have been on the cider!

 

[WayneL]

because if they were still connected (depending on a few things) it would make a difference to the readings

I don't understand how it would make a difference to any readings, if the conductors are connected to their relevant bars and the mcb - you will have to be more specific.
- obviously the main switch is open at this time or you shouldn't be poking around in the CU anyway

 

[Johno]

who said he had opened the main switch, he might have just turned it off in the house