R1+R2 - two way lighting - 2.7 ohms, can i get your opinions please?

[SJD]

Which scheme will be assessing you? It is not unknown for a scheme to insist the value has to be under 100 Ohm - and the scheme in question believes it has more authority than BS7671!

 

[SPARTYKUS]

No offence, but you are going to have to really brush up for your assessment, they wont hold your hand, they will expect you to know. Understand what Ze, Zdb & Zs mean. Also when you test,you need to have expected values, otherwise you are just guessing. Like Dillb said read GN3, and then read it again, it is all in there mate.

GN3. Riveting.

 

[TJ Anderson]

TJ Anderson - This was what I thought, but somehow my 145 ohms reading on a TT (under 200 is considered stable) has got everyone suggesting not to use a rod..?

That is their preference and obviously lower is better. IET On site guide says over 200 is considered unstable so it there in black and white.

 

[Simonslimline]

Simonslimline - Sorry, this is my first garage (outbuilding), so ZE is at origin at main House supply. What is the equivalent at the garage end..

Ze from the origin.

Zdb from the garage board. In regards to the max value, it depends on the OCPD protecting the SWA submain.

 

[srl-8]

Which scheme will be assessing you? It is not unknown for a scheme to insist the value has to be under 100 Ohm - and the scheme in question believes it has more authority than BS7671!

Not NICEIC, Stroma. I will check to see if they are happy with the 144 reading

 

[srl-8]

swa protected via a 30amp mcb.

 

[telectrix]

with a PEFC of < 2 A, i can't see anybody being happy ( except of course the cure-all RCD )

 

[TJ Anderson]

Not NICEIC, Stroma. I will check to see if they are happy with the 144 reading

Just show him your onsite guide. I very much doubt Ra will be an issue. The R1 + R2 will, so get that sorted.

 

[Leesparkykent]

swa protected via a 30amp mcb.

do you know the type? And the maximum Zs permitted for this mcb?

 

[TJ Anderson]

with a PEFC of < 2 A, i can't see anybody being happy ( except of course the cure-all RCD )

Yeah . The new regs might only have 3 regs in it. 1. 30ma RCD for all circuits 2. Max Zs 1667 Ohms whatever it is. 3. Now do what you like!!

 

[telectrix]

and a RCD that hasn't been tested for donkeys? i'd rather rely on a tried and trusted method of disconnection. too much faith is placed in these made to a price, not quality, get out of jail free, if you can't provide a decent earth. either use the pme or install some decent rods.

 

[srl-8]

do you know the type? And the maximum Zs permitted for this mcb?

Yes, max ZS is 1.24.

 

[Leesparkykent]

Yes, max ZS is 1.24.

so if you are going to extend the equipotential zone your zdb should be under this.

 

[David M]

Is your tester calibrated, and working correctly? Is it worth testing the installation with a different meter just for peace of mind?

I, d be inclined to check the connections regarding that high R1 + R2 reading. Most likely something as simple as a poor termination.

Regarding the earth rod, although acceptable I wouldn't be happy with that reading. Surely using the swa armour is a better option if it is indeed an option?

 

[Octopus]

Not NICEIC, Stroma. I will check to see if they are happy with the 144 reading

hum, Stroma assessments, to my knowledge are far more extensive than the others so I hope you brush up a lot before you sign the cheque.

And why did you do live tests knowing that the dead tests were very high?