Zdb before dead tests.

[swaley]

Hi guys got my assesment in 3 weeks and want to get my testing spot on. Little confused whether to test Zdb on 2 way CU before dead tests?? Or do I jump straight into continuity? Thanks in advance.

 

[gazdkw82]

A separate board requires a separate test sheet and will have its own ze/z's. Zdb would not exist because the test sheet will have the board indentification information.

That's the way its always been taught at college

 

[telectrix]

think i'll go for Zzzzzzz s. time for my morning nap.

 

[Risteard]

A separate board requires a separate test sheet and will have its own ze/z's. Zdb would not exist because the test sheet will have the board indentification information.

That's the way its always been taught at college

It won't have its own Ze. Ze is external to the installation and therefore there can only be one.

 

[gazdkw82]

Yes your right. Will have its own zs and should be a separate sheet.

No zdb needed ?

 

[JK-Electrical]

So maybe it should be called a ZeZdb

​

 

[Deleted member 26818]

I’ve left you guys to this for a few days to sort out, but I see there is still some confusion.

BS7671 requires every installation to have a Main Earth Terminal, and that every CPC and PBC within the installation shall be connected to the MET.
In the scenario I postulated there is a second installation which is supplied from the first installation.
This second installation has it’s own earthing arrangement and own MET.
As such the Earth Loop Impedance should be recorded as Ze.
However, as the second installation is supplied from the first installation and Ze has already been recorded, and similarly the Zs of the distribution circuit supplying the second installation has been recorded, Zdb is often used to avoid confusion.

If however you wish to produce two separate EICs or EICRs, or record Ze for both installations on the one EIC or EICR, that’s totally up to you.

 

[Ian1981]

However you want to spin it there’s only on ZE to an installation.
How can they be a second installation fed of the ‘first installation ‘ its one installation.

 

[Rpa07]

Now we’ll argue the definition of installation for another 4 pages -
Hobnobs or digestives with your tea?

However you want to spin it there’s only on ZE to an installation.
How can they be a second installation fed of the ‘first installation ‘ its one installation.

 

[Octopus]

Surely it can only be 2 installations if there are 2 separate incoming supplies .......

 

[Deleted member 26818]

However you want to spin it there’s only on ZE to an installation.
How can they be a second installation fed of the ‘first installation ‘ its one installation.

One Ze per installation, how many METs per installation?

 

[Deleted member 26818]

Surely it can only be 2 installations if there are 2 separate incoming supplies .......

Block of six flats, one supply to the block, how many installations?

 

[Octopus]

Block of six flats, one supply to the block, how many installations?

1 per metered supply so probably 7

my post could have been clearer

 

[Deleted member 26818]

1 per metered supply so probably 7

my post could have been clearer

There did use to be something in the 14th Edition stating the origin of an installation was at the customer connection point at the meter.

 

[Wilko]

One Ze per installation, how many METs per installation?

Hi - I was taught only 1 MET too. Any subsequent "look alikes" were called EMT (earth marshalling terminals).

 

[Deleted member 26818]

Hi - I was taught only 1 MET too. Any subsequent "look alikes" were called EMT (earth marshalling terminals).

An EMT (not a term used in BS7671) would still be connected to the MET.