Help with EICR code!

[hoppy]

Hi,

just wondered what your thoughts are on this,

3 bed town house

Whole house ring final, mixture of 2.5 / 1.0 & 2.5 / 1.5 twin and earth cables,
End to ends = 0.78, 0.78, 1.6. R1r2 = 0.61 (spur).
ZS = 0.66!
BS7671 recommends a max of 100 square meters which using 2.5/1.5 = an r1r2 of 0.48.

Thus the readings appear that the circuit is over 100 square meters, as the max end to ends of line and neutral should be 0.72!

the zs is within the max for b32!
would you code 3 this or simply ignore it , as it is not unsafe, am I being too cautious?

 

[uksparks]

It could still be under 100m because you are unable to see how it's routed and all the cables are hidden in the fabric of the building.

So long as it complies on the disconnection time, that's the main thing.

code it? Erm no I wouldn't as if it's under the limit, there's not much to say.

 

[Plonker 3]

Why code it, all R1+R2, R2 and continuity tests are for is too ensure conductors are either continuous ( a ring), polarity and too ensure your CPC is present.

 

[uksparks]

Why code it, all R1+R2, R2 and continuity tests are for is too ensure conductors are either continuous ( a ring), polarity and too ensure your CPC is present.

I was just going to add that.

 

[hoppy]

Thanks guys

the reason I asked is I am subbing to a firm and their qs said that if the r1r2 on a ring is over 0.48 then this does not comply and the ring should be split into 2 radials, which I believe is complete nonsense!

 

[Plonker 3]

Thanks guys

the reason I asked is I am subbing to a firm and their qs said that if the r1r2 on a ring is over 0.48 then this does not comply and the ring should be split into 2 radials, which I believe is complete nonsense!

As always, ask him why they think this.

 

[Silly Sausage]

As always, ask him why they think this.

No, not why they think, get them to technically justify their opinion.

 

[GLENNSPARK]

Thanks guys

the reason I asked is I am subbing to a firm and their qs said that if the r1r2 on a ring is over 0.48 then this does not comply and the ring should be split into 2 radials, which I believe is complete nonsense!

thats bullshyte...simple as that....what you`v been told there....

and he`s supposed to be a QS....god help us...and this is exactly why the whole QS system needs overhauling...by someone outside the scams influence....

 

[NDG Elecs]

Why code it, all R1+R2, R2 and continuity tests are for is too ensure conductors are either continuous ( a ring), polarity and too ensure your CPC is present.

Yep, agree. Would also add that the end-to-end results could indicate poor or oxidised connections.

Hoppy, you say BS7671 r1r2 max is 0.48 and you got 0.61 for a spur....so if that's a spur what were the other r1r2's?? They must have been lower obviously. ie close to 0.48.

Dont forget that the CPC is 1mm in parts, so that will push up the r1r2 a smidgeon.

 

[Badged01]

BS7671 recommends a max of 100 square meters

Sure your not confusing the BS7671 app 15 recomendation for max area served? I can't seen anything in BS7671 that mentions 100m as a length but happy to be pointed at the reg.

the max end to ends of line and neutral should be 0.72!

Assuming BS7671 states a max length of 100M then for 2.5mm the resistance =7.41 mohm/M. For a 100M length your end to end reading should be ~ 0.74ohm If you're getting 0.78 then I dont see any issue -- its close enough for cash within all the variations of measurement!

Or am I missing something fundemental as I haven't had my second morning coffee & cognac yet .......

 

[hoppy]

Thegayowl, the ring r1r2 was 0.58 the spur is close to it's feeding socket!

thanks for the replies! Just gonna leave it as is!

 

[MDJ]

Sure your not confusing the BS7671 app 15 recomendation for max area served? I can't seen anything in BS7671 that mentions 100m as a length but happy to be pointed at the reg.



Assuming BS7671 states a max length of 100M then for 2.5mm the resistance =7.41 mohm/M. For a 100M length your end to end reading should be ~ 0.74ohm If you're getting 0.78 then I dont see any issue -- its close enough for cash within all the variations of measurement!

Or am I missing something fundemental as I haven't had my second morning coffee & cognac yet .......

You won't find it either, unless it is on the back of a cornflakes packet

 

[Richard Burns]

The on site guide gives 106 m as the max length of a standard ring final.

 

[MDJ]

Whats the reg number Richard? My OSG has been in the portaloo on site for a while, thats all it is good for IMO

 

[Richard Burns]

I do not think there is a reg number, this is the basic guide to standard circuits that gives the "standard" types of circuits that you can install and then specifies the maximum lengths and the reasons for these, it is quite a large table over several pages.
Basically it is if you do not want to calculate anything, this is a guide to limits.

 

[MDJ]

I do not think there is a reg number, this is the basic guide to standard circuits that gives the "standard" types of circuits that you can install and then specifies the maximum lengths and the reasons for these, it is quite a large table over several pages.
Basically it is if you do not want to calculate anything, this is a guide to limits.

oh okay, I see cheers.

 

[Badged01]

Its not a reg as such, just guidance/interpretation of the regs for standard circuit designs based on set conditions (e.g. assumes TN-C-S Ze = 0.35 ohms). Could have saved me bags of time doing all my circuit design calcs by hand from 1st principles!!

Need to read the OSG more ........

 

[sparkymalarky]

I would only be concerned if the end to end tests were way out from each other say : Line 0.48 Neutral 0.68. Rule of thumb is 0.05 Ohms. Anything more than this and then it comes down to one or more connections being poorly made etc. I would be happy if the end to end readings were appropriate, insulation resistance was satisfactory and that the Zs values conformed. Also if you scan through BGB, it notes that ''historically a limit of 100m² has been adopted''. This is purely a guide.

 

[Geoffsd]

Does any one know what relevance 100 square metres has to anything. ?

A ring around a 10m square area would only be 40m.

50m x 1m would be 102m.

 

[telectrix]

Does any one know what relevance 100 square meters has to anything. ?

A ring around a 10m square area would only be 40m. but with 10 sockets, 2.5m drop per socket that's another 50m of cable.

50m x 1m would be 102m.

see above.