Connecting the neutral directly to the neutral bar

[Lintay]

Hi all, is it ok to connect the main incoming neutral to a 3 phase db directly to the neutral bar and avoiding the main isolator?
Thx

 

[Leesparkykent]

Hi all, is it ok to connect the main incoming neutral to a 3 phase db directly to the neutral bar and avoiding the main isolator?
Thx

Earthing arrangement? Is it a 3phase supply or single phase and link kit?

 

[Lintay]

Hi lee, yh it's a three phase supply, thx

 

[Ian1981]

If it’s TT and a 3 phase db then a 4pole isolator is required to break the neutral as well.

 

[Lintay]

The db came with a 4 pole isolator but I've been told it's ok to connect it straight to the neutral bar?
Surely this is bad practice?

 

[Ian1981]

The db came with a 4 pole isolator but I've been told it's ok to connect it straight to the neutral bar?
Surely this is bad practice?

If you’ve got a 4 pole isolator then use it.
Generally tho in a TN system you can use a 3 pole isolator to isolate the phases only,as the neutral is considered to be around the same potential as earth as they are connected together at the transformer/supply end.
TT 3 phase supply then the neutral needs to be isolated also.
Generally there’s a neutral terminal on the main switch with 3 pole type on some manufacturers types were the neutral connects but isn’t switched.

Domestic single phase consumer units tho require double pole isolation as used by ordinary persons or unskilled electrically or whatever the hell it is nowadays.

 

[Ian1981]

 

[westward10]

Assuming a TN system then yes but there must be a disconnecting link on the neutral bar.

 

[Lintay]

Does it make a difference if it's a submain on a tn system?

And also why do u need a 4 pole isolator on a tt and not a tn system?
Thx

 

[westward10]

Doesn't matter the means of supply for a TN system, submain or the origin. Neutral is deemed to be at earth potential on TN systems and there is no requirement to isolate it. This is not the case for TT and isolation is required.

 

[Lintay]

Thx westward

 

[Leesparkykent]

Is there a UPS? If so probably s bad idea to break the neutral,

 

[MJPD29]

why would you want to do this? surely it'd be easier to connect it to the isolator as the other 3 phases are going there too

 

[sam400]

Is there a UPS? If so probably s bad idea to break the neutral,

That's interesting - why is that Lee?

Cheers

 

[Leesparkykent]

That's interesting - why is that Lee?

Cheers

Because it common for a UPS to use the neutral as a reference for output voltage . If the neutral is broken and the ups kicks in then there could be a lot of fried equipment.

 

[MJPD29]

Never knew that and came across a UPS in a shop after the main 4 pole isolator was reset by staff in an attempt to reset a single rcbo.... interesting

 

[Risteard]

As Lee says there can be good reason not to break the neutral for safety reasons. Obviously without knowing anything about the supply or Earthing arrangements etc. we cannot really advise in this instance. There simply hasn't been enough information.