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.

 

[Wilko]

Hi - agree, it's mentioned in GN8 p69 .

 

[Deleted member 26818]

We have Regulation 542.1.3.3:
“Where a number of installations have separate earthing arrangements, any protective conductors common to any of these installations shall either be capable of carrying the maximum fault current likely to flow through them or be earthed within one installation only and insulated from the earthing arrangements of any other installation.

In the latter circumstances, if the protective conductor forms part of a cable, the protective conductor shall be earthed only in the installation containing the associated protective device.”

The last sentence of this Regulation indicates that one installation can supply another.

 

[Ian1981]

2 installations may have a common supply as it where say at the cut out however one installation feeding as you say another is just one installation as in a supply feeding a external building fed from one consumer unit whether you TT the other end or not.
2 Consumer units fed from one cut out such as a split load DB and say a 2 way shower DB , tails in Henley blocks maybe considered 2 installations by some.

Some consider one supply equals one electrical installation regardless.

 

[Midwest]

 

[JK-Electrical]

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.

I use Easy Cert for all my certificates. The software allows the user to add an unlimited number of additional distribution boards to the certificate along with additional test schedules. So, if, for example, I'm testing a domestic installation that comprises of a consumer unit located at the source of the installation which in turn supplies a second consumer unit located in a garage, I would simply record the test results obtained from each board on two separate pages of the same EICR/EIC with the location and functionality of each board clearly stated. Works for me!

 

[JK-Electrical]

 

[Deleted member 26818]

2 installations may have a common supply as it where say at the cut out however one installation feeding as you say another is just one installation as in a supply feeding a external building fed from one consumer unit whether you TT the other end or not.
2 Consumer units fed from one cut out such as a split load DB and say a 2 way shower DB , tails in Henley blocks maybe considered 2 installations by some.

Some consider one supply equals one electrical installation regardless.

I refer you again to the last sentence of 542.1.3.3.
Seems to me, to exactly describe a TT’d shed.

One problem with treating the two installations as one, is compliance with 542.4.1:
“In every installation a main earthing terminal shall be provided to connect the following to the earthing conductor:
(i) The circuit protective conductors
(ii) The protective bonding conductors
(iii) Functional earthing conductors (if required)
(iv) Lightning protection system bonding conductor, if any (see Regulation 411.3.1.2).

No mention of two METs, one for the house and the other for the shed?

 

[Midwest]

See someone's put reel two on, just got back to me seat in time