Zdb ok but no R1 + R2

[Delboy10]

Hi All i know its late friday, but try and help me out with this one if you can.
Just got in now from work on the way home a landlord called me to ask if i could test a communal DB he has at an HMO.
I decided to have a look on the way home, long story short each flat was feed from this DB including the communal circuits(lights,sockets).
so i checked Zdb to each flat which was ok but when i did R1+R2 test on the supply cable to each flat i got nothing,tried to each flat and 4 out of the 5 came back with a zero reading.
Distribution board was contactum,each flat was feed from a 40 amp b type mcb (No RCD on DB).

Any thoughts as its got me wondering, the Zdb to each flat was ok but R1+R2 no reading at all.

 

[Deleted member 9648]

What was the distribution cable to each flat?.....Are you sure you were testing each distribution circuit with the L-E linked out at the other end?....

 

[SimpleSimon]

An r1+r2 is a dead test, you were doing a dead test right?

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[SPARTYKUS]

When you say "zero reading" do you mean that or do you mean no reading/ open circuit? Zero would be a great reading.

 

[spamwize2]

Hi you must be taking readings from somewhere other than phase and earth? How are you checking each flat?..
1. have you got Zs and Ze to compare?

 

[Delboy10]

each flat had a 10mm t+e feed from the distribution board,and yes i am sure i was testing each distribution circuit with the L+E linked out,

 

[Delboy10]

yes mate it was tested dead

 

[Delboy10]

sorry i meant no reading i.e open circuit as you say

 

[spamwize2]

so have you got Ze?

 

[fuzzydunlop]

........

 

[Delboy10]

i am taking my readings from phase and earth to each flat from the main distribution board is dead with the earth and phase linked out.
i thought it might be my tester (fluke 1653)but i checked my own house when i got back tested fine,double checked the cal quickly witb my cal card.all ok.i have zs and ze for the installation,i will post those tomorrow as i am out at the inlaws at the moment so i will post it in the morning.

 

[spamwize2]

As we all know Zdb is a reading where all earth connected:
to get Ze we do what?

 

[Delboy10]

remove the main earth from the distribution board so to prevent parallel paths

 

[spamwize2]

ok try that u will be sorted. Zdb will be within tolerance easy

 

[Amp David]

Even if hes testing with main earth and bonding connected, then removing them ain't going to make an R1 R2 figure appear.

Must be testing wrong, if submains are T and E then can't see how R2 can be lost

 

[Delboy10]

i agree with your post but i am positive i am testing it correctly,as i said in my original post,4 out of the 5 came back open circuit,but 1 which was the top floor flat tested ok R1+R2.
thanks for your input fellas i will try R2 method on monday and report back

 

[Amp David]

The only way as ou say, get out the wander lead and test R2 of the distribution cables

 

[SimpleSimon]

Even if hes testing with main earth and bonding connected, then removing them ain't going to make an R1 R2 figure appear.

Must be testing wrong, if submains are T and E then can't see how R2 can be lost

But if he,s getting a Zdb reading he could be getting yhis through parrell paths of the bonding. When in actual fact he's got no earth. :thumbdown:

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[i=p/u]

try linking the neutral, see if loop then you know is earth, is you main switch closed

 

[Hawk81]

By any chance have you switched each mcb off and linked from the output of one mcb to the earth bar on the CU this would give you the readings you describe?

 

[Amp David]

But if he,s getting a Zdb reading he could be getting yhis through parrell paths of the bonding. When in actual fact he's got no earth. :thumbdown:

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Yeah I know that

 

[SPARTYKUS]

Hi All i know its late friday, but try and help me out with this one if you can.
Just got in now from work on the way home a landlord called me to ask if i could test a communal DB he has at an HMO.
I decided to have a look on the way home, long story short each flat was feed from this DB including the communal circuits(lights,sockets).
so i checked Zdb to each flat which was ok but when i did R1+R2 test on the supply cable to each flat i got nothing,tried to each flat and 4 out of the 5 came back with a zero reading.
Distribution board was contactum,each flat was feed from a 40 amp b type mcb (No RCD on DB).

Any thoughts as its got me wondering, the Zdb to each flat was ok but R1+R2 no reading at all.

Alright Delboy

Interesting thread btw.

Having re-read your opening post, I can only surmise that R2 for the sub main is broken for 4 of the 5 flats. As others have pointed out you may very well still get a cracking Zdb via parallel paths (spesh if Bonding in place for water service in each flat for example and this runs via pipework back to DB1 - the origin board so-to-speak).

So Mr R2 test will reveal all. Hopefully.

 

[Hawk81]

Why is everyone missing the obvious here? I find it hard to believe that 4 out of 5 flats have a broken R2 in the supply cable

 

[i=p/u]

open switch isolater... i know

 

[Amp David]

Can't be that simple?

OP is going to be aware of any switch isolators as he'd have to be closing then to get his Zdb

 

[keniff]

Hawk 81 bang on with this, mcb's are open and there for no line to flat, link out from breaker output to earth bar on each individually

 

[SPARTYKUS]

Don't mean to deflate anyone, but it's hard to say really without actually being there !

Let us know Delboy

 

[keniff]

Don't mean to deflate anyone, but it's hard to say really without actually being there !

Let us know Delboy

As always!! Never know what your gonna find on any job....

 

[VMan]

Are you sure the circuits are labeled correctly???

i.e you linked r1+r2 at DB circuit labeled flat1, testing at flat 1 but the r1+r2 circuit is actually flat 4?

 

[SPARTYKUS]

Are you sure the circuits are labeled correctly???

i.e you linked r1+r2 at DB circuit labeled flat1, testing at flat 1 but the r1+r2 circuit is actually flat 4?

Ohhhh thats good, didnt think of that. Nice one