Tp+n Dis Board

[LankyWill]

Morning All

I have a Hager TP+N Dis Board that i am installing later on this week. I need to purchase the switch disconnector for the board separately. Im unsure of which type to buy as i am getting conflicting statements.

Its Between:

4 pole 250A Switch Disconnector
3 pole 250A Switch Disconnector.

As its a TP+N board i thought the 4 pole would be better but one of the old boys say if their is a borrowed neutral it could become live!

 

[Leesparkykent]

What's the earthing arrangement?

 

[snowhead]

Are they all 3 phase balanced loads or are there some single phase loads?

 

[Leesparkykent]

3 pole

What if its TT? would you still install a 3 pole isolator/incomer?

 

[snowhead]

What if its TT? would you still install a 3 pole isolator/incomer?

I assume it's not TT or its a sub board otherwise the O.P wouldn't have needed to ask.

 

[Leesparkykent]

Unless its TT then there isn't really going to be a requirement to install a 4pole incomer. Installing a 4 pole incomer could be a bad move if there were to be a UPS or similar referenced to neutral on the load side of the incomer.

 

[LankyWill]

Thanks for the help

Its a TNS earthing arrangement, 3 Phase with 400A per Line. This would be fed directly from the panel board on a 160A MCCB. When would you favour the 4 pole switch disconnector?

 

[Wilko]

Hi - 537.2.1.1 says not necessary to switch the neutral if it is known to be reliably connected to earth via a suitable low impedance (as should be in your TN-S). In case others read this, for single phase domestic or similar then 537.1.4 applies and says we shall provide an isolation switch for both live conductors. Cheers, David.

 

[LankyWill]

Hi - 537.2.1.1 says not necessary to switch the neutral if it is known to be reliably connected to earth via a suitable low impedance (as should be in your TN-S). In case others read this, for single phase domestic or similar then 537.1.4 applies and says we shall provide an isolation switch for both live conductors. Cheers, David.

Cheers Wilko thats a good bit of info thier.

 

[7029 dave]

Hi - 537.2.1.1 says not necessary to switch the neutral if it is known to be reliably connected to earth via a suitable low impedance (as should be in your TN-S). In case others read this, for single phase domestic or similar then 537.1.4 applies and says we shall provide an isolation switch for both live conductors. Cheers, David.

I would keep the N closed too.