Slightly high ZS reading

[andyww]

Hi

Have installed a new ring circuit - for a kitchen - lots of points (19 in total) - TNS earthing, max ZS should be 1.16 - I'm getting 1.41 - have checked tightness of all terminations and all are good

anyone got any ideas?

Cheers

 

[monkeyelectric]

What are your r1+r2 readings? how long is the run and is it just the kitchen on it?

What is your ze reading?

 

[leonard290]

Hi

Have installed a new ring circuit - for a kitchen - lots of points (19 in total) - TNS earthing, max ZS should be 1.16 - I'm getting 1.41 - have checked tightness of all terminations and all are good

anyone got any ideas?

Cheers

cable length.should have split into two rings. zs=ze+r1+r2.table 9a on site guide

 

[Guest123]

max ZS should be 1.16

Why???

Max Zs in BS7671 for a 32A type B is 1.44ohms.

What breaker do you have??

Test certs ask for the max permitted by BS7671 not the corrected values in OSG.

 

[Des 56]

But the circuit still has to comply
The Zs reading then multiplied by 1.2 will be 1.73

Lower the breaker rating
Split the ring into 20 amp radials
Install supplementary bonding but,
probably re test with another meter,just to be sure before butchering

 

[Spudnik]

So then fellas, what max should we be using??

 

[ajelec10]

The circuit should be RCD protected which provides supplementary portection against an earth fault so it would be fine. i think?

 

[andyww]

Ze is 0.35. R1 & R2 is 0.44

 

[Des 56]

If it was TT and then 1667 ohms,so relying on the RCD we can assume the same


I can see that this is going to return to the"Is ZS testing worthless thread"

 

[Spudnik]

Im thinking there is a dodgy connection somewhere.

 

[Des 56]

Ze is 0.35. R1 & R2 is 0.44

So your Zs is 0.79 ?

 

[andyww]

it is by adding Ze and R1&R2 - but testing Zs at socket with my Megger gives a reading of 1.41

I've checked all the connections and all are fine

 

[Spudnik]

Thats the reason why Zs should not be calculated.

New sockets can also give strange readings due to contacts inside.

Try pushing the plug on your tester in and out a few times to 'clean' the contacts.

 

[andyww]

will give it a go

Thanks all

 

[kung]

Thats the reason why Zs should not be calculated.

New sockets can also give strange readings due to contacts inside.

Try pushing the plug on your tester in and out a few times to 'clean' the contacts.

Put an extra socket at me mums for a minor on NIC assessment but couldnt do Zs as kt61 hasnt got no trip function and alto al4588 loop isnt cal'd so done Ze and got 6.2ohms lol phoned me old m8 at SSE and within 45mins a guy was there and now got PME with Ze of 0.13ohms The CU was changed about 5yrs ago by a supposed sparks when me dad was alive but no tests/certs etc even used a bs951 on supply for earth & that was loose ! wasnt even touching anything but tape !
Dont know why we bother ! im sick of finding shoddy work he had even put a socket in the frt rm with NO cpc !