IR on a whole board

[the pict]

When testing IR on a 3 phase and N where the N cannot be swiched is it considered safe practice to disconnect the incoming N from it's stud
Pict

 

[telectrix]

IMO only if the board is totally isolated. and even then, treat it as a live conductor.

 

[Guest123]

IMO, if the entire installation is safely isolated and all electronice equipment is disconnected (I'm thinking emergency lighting here) there should not be any current flow in any of the line conductors ergo there shouldn't be any return current flow in the neutral conductor.

For safety's sake I would terminate the supply neutral tail into a connector block of some description for the duaration of the test just as an added precaution.

 

[the pict]

I use one of those all plastic spring clamps, I can get the bared copper completly enclosed, I was just wondering what the "offiical" line was and GN3 says nowt about it, I might run it past my NICEIC area rep although it will probably be a case of what we in Scotland call "skelfs in the erse" from sitting on the fence
Pict

 

[sparkyeis]

Leave that neutral connection where it is connected, theres no need to disconnect test in place!

Cheers James

 

[the pict]

Will that then not go up the L&N joined back to E via the tranny or is my mental picture of the route wrong
Pict

 

[sparkyeis]

You are always going to get a 'dead short' reading if it is TNC-S (PME) any how. Years ago when I worked for hydroboard it was common practice to fit a swivel link on the neutral along with the earth. We were always taught to carryout IR on circuits before final connections to DB's

 

[oxocube]

The neutral has to be disconnected to do the N-E IR test. Personally I would disconnect and immediately do the N-E test and then reconnect the neutral.

The reason for my method, if there are downstream single phase circuits and you forget to reconnect the neutral. And then close the 3 phase switch you will put 400v across the single phase loads. And you would not be very popular if you did that.

 

[the pict]

Many Many years ago I was fitting a single pole MCB to a three phase board which was in a cupboard full of junk I knelt on a table leaned across some boxes and fitted the breaker, but caught two prongs of different phases, jeez what a bang, I took out the isolator and vapourised the copper prongs, just because they did not want the power of during lunches, I learnt a two valuable lessons one I am not immortal and two safe isolation is done for a reason. So Oxo your right, your only popular if no one knows you even in the building.
Pict