Max Zs for earthing arrangement?

[DiscoDave]

as per OSG pg 11,

TN-C-S = 0.35
TN-S = 0.8
TT = 21

But where is this in the regs? It's been doing my head in for the last half hour and i know i'll kick my self when some one points it out but please help cos it's not funny any more!

 

[DurhamSparky]

actually 21 ohms for tt is the distributors "ROD" not the consumers!! BRB states less that 200 ohms for TT, (unless your NICEIC) and they write there own rules and want 100 ohms...

im searching the books as well now cheers!!!

 

[caddy]

As far as I am aware the fiqures for TN-S and TN-C-S have nothing to do with BS7671 as they are values outside the consumers installation and therefore would be under the suppliers regulations. Reference is made however in BS7671 under 313 and appendix 2 they appear only to be listed in the OSG for convenience.

For a TT installation refernce is made at 411.5.3 and Table 41.5 Note 2

hope it helps..

 

[DurhamSparky]

i gave up after reading apendix 2 para 2...!! it goes on about supply and continuity regs 2002... (supplier)

 

[caddy]

i gave up after reading apendix 2 para 2...!! it goes on about supply and continuity regs 2002... (supplier)

I know i did as well. But basically the figures quoted arent in BS7671 as they are outside the scope of BS7671, they come under Quality and Continuity regulations 2002.

 

[ezzzekiel]

Re: Max Zs for earthing arrangement?

TN-C-S = 0.35
TN-S = 0.8
TT = 21


are we sure they are max ZS figures?

 

[Sparky Ninja]

Re: Max Zs for earthing arrangement?

TN-C-S = 0.35
TN-S = 0.8
TT = 21


are we sure they are max ZS figures?

Are we looking for an E?

 

[ezzzekiel]

yeah gimme an e please bob..........

 

[DiscoDave]

well at least i'm not on my own! but sorry for making some of you hunt it out too! I shall sleep easy tonight!

 

[DiscoDave]

are we sure they are max ZS figures?

Sorry *slaps back of hand* I knew what i was on about!

 

[Amp David]

Sorry *slaps back of hand* I knew what i was on about!

Its a good job everyone else did too then