r1 r2

[ban-all-sheds]

However if you want to suggest a ball park figure at which you would consider the ELI to be acceptable when a RCD is used I am not stopping you.

Measured? 80% ROT?

B6 - 6.4Ω

 

[Spark123]

Off top of my head is it not a tad lower for a B6 under the 17th edn?

 

[ricicle]

6.13 ohms

 

[GaryMo]

6.13 ohms

Correct:

(230 / (6 x 5)) x 0.8

 

[ban-all-sheds]

6.18Ω according to Table B4 in GN3.

IHNI why I posted the figure from Table 2D the 16th GN3....

But looks like a misprunt - should be 6.13Ω

 

[ricicle]

6.13 ohms

Correct:

(230/(6 x 5)) x 0.8

 

[GaryMo]

Lol

 

[ban-all-sheds]

Or even 6.4 x 230/240...

 

[mikhailfaradayski]

So I am open to be told how common TN-S supplies are in standard domestic dwellings, confirmed by the DNO, but not going to hold my breath waiting for replies. Really only people who can tell us are those who work for DNO's and would be interesting to hear from them.

My house is TNS, so are my neighbours either side. My mums house is TNS, So were the last 2 re-wires i did. Had an old cast iron cut out and meter changed last week, watched the e-on guys wack the old one to bits and replace with a new one. It started as a TNS when they arrived and they left it as a TNS.

I bet theres thousands of them all over the country. I would probably agree with the earlier post that TT accounts for about 10% of supplies and a fairly even split between TNS and TNCS for the remainder

edit- whats more, when i asked if they should ensure that the ELI should be in spec, the hands-in-pockets-standing-watching guy merely sniffed and said "on this street, 0.2, we've checked the polarity (with bulb set to earth) and it lit up so therefore its ok"

Who needs calibrated test equip. when you work for the dno?

 

[Spark123]

6.18Ω according to Table B4 in GN3.

IHNI why I posted the figure from Table 2D the 16th GN3....

But looks like a misprunt - should be 6.13Ω

I don't think it is a misprint, instead of using 80% try dividing it by 1.24, 1.24 given by the temperature coefficient for copper 0.004Ω/ºC and a change of temperature of 60ºC.

230 / (5x6) = 7.66667Ω
7.66667Ω / 1.24 = 6.18Ω

 

[bongos]

My house is TNS, so are my neighbours either side. My mums house is TNS, So were the last 2 re-wires i did. Had an old cast iron cut out and meter changed last week, watched the e-on guys wack the old one to bits and replace with a new one. It started as a TNS when they arrived and they left it as a TNS.

I bet theres thousands of them all over the country. I would probably agree with the earlier post that TT accounts for about 10% of supplies and a fairly even split between TNS and TNCS for the remainder

They're all TN-S round here with the old PILC installed. On the jobs i've been helping out with there's been only one TN-C-S, which was converted from TT when they had 3 phase put in.

I reckon the majority of all the urban areas would still be TN-S, maybe excluding new estates?