Zdb Question

[newtothis]

Ze would be taken as normal, it would be named Zdb though.

I seen this thread earlier did some research and this seems as close to a diffinitve answers as I've seen.
Open question: If it's not, why isn't it ?

 

[uksparks]

Here's a question regarding Zdb.

when changing a consumer unit in a property that has sub mains, do you just test up to the sub main and ignore it from there on? I can only assume so, well that's what I do, you can't be responsible for the circuits off the submains.

 

[Andy78]

Here's a question regarding Zdb.

when changing a consumer unit in a property that has sub mains, do you just test up to the sub main and ignore it from there on? I can only assume so, well that's what I do, you can't be responsible for the circuits off the submains.

Can't you ? A separate SOTR is in order here appended to the rest of the paperwork.

 

[Andy78]

I seen this thread earlier did some research and this seems as close to a diffinitve answers as I've seen.
Open question: If it's not, why isn't it ?

See posts #5 and #6 for the correct definition and explanation.

 

[davesparks]

Here's a question regarding Zdb.

when changing a consumer unit in a property that has sub mains, do you just test up to the sub main and ignore it from there on? I can only assume so, well that's what I do, you can't be responsible for the circuits off the submains.

No you test the submain, how would you go about testing up to the submain anyway??
Final circuits fed via that submain you wouldn't necessarily expect to be tested.

 

[davesparks]

Zdb is Zs so it is acceptable to measure or calculate. That's what the BYB says isn't it?

Any bonding is at the MET or EMT, not any other boards.

Tin hat on obviously!

Main bonding should be connects back to the MET or EMT but it could go via a subDB.

 

[davesparks]

We remove the bonding cables to get an accurate Ze and because we cannot presume the resistance value of the bonding will be a stable figure, however when we measure Zs we leave the bonding in place so we are using part of that 'instabilty' in our 'measured' value of Zs??
.

No, that's not the reason.
We measure Ze without the main bonds connected to ensure that the reading we get is the earthing system and not the extraneous parts, thus we ensure that we are actually testing the ,means of earthing.
Measuring With the bonds connected could actually be testing via the neighbours means of earthing via a common metallic service and fail to identify a broken/high resistance suppliers earth.

 

[uksparks]

No you test the submain, how would you go about testing up to the submain anyway??
Final circuits fed via that submain you wouldn't necessarily expect to be tested.

Thats what I usually do, test to the next layer / db at the end of the sub main. It depends, if it's off the board I would but if on Henley blocks I wouldn't.