• IMPORTANT: Please note that nobody on this forum should be seeking from or providing advice to those who are not competent and / or trained and qualified in their field (local laws permitting). There is a discussion thread on this global industry-wide matter HERE. This also has more information about the warning with regards to sharing electrical advice in some countries. By using this forum you do so in agreement to this.

Discuss Zs from board supplying another board in the Electrical Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

Ze is only at the origin, the rest are Zs.

Measure/calculate the R1+R2 for each distribution circuit and add the Ze. (Zs=Ze+(R1+R2))
 
I have a ccu with a Ze of 0.09 and it's supplying another ccu which that board supplies multiple other CCUs I was wondering how I would work out my zs and ze on the other boards?

Ze only exists at the origin, e stands for external.

In an existing installation you measure Zs at each board.

If this is at the design stage then you need to use the calculated impedance of the circuit and add it to the Ze quoted for the supply.
 
Ze is only at the origin, the rest are Zs.

Measure/calculate the R1+R2 for each distribution circuit and add the Ze. (Zs=Ze+(R1+R2))
Does it not become Zs at DB? from board to board, I hear what you're saying, but does my statement not hold water in this case?
 
Does it not become Zs at DB? from board to board, I hear what you're saying, but does my statement not hold water in this case?

Yes it does become the Zs at the DB, but obviously that is also the Zs of the distribution circuit because they are one and the same thing.

Strictly speaking 'Zs at DB' or 'Zdb' are not correct terminology, much like 'ring main' instead of 'ring final circuit', everyone knows what is meant by it, it's commonly used, but it's not correct terminology.
 
Does it not become Zs at DB? from board to board, I hear what you're saying, but does my statement not hold water in this case?
Each board would have its own Zs, sometimes referred to a Zdb. I think we're saying the same thing.
 
Yes it does become the Zs at the DB, but obviously that is also the Zs of the distribution circuit because they are one and the same thing.

Strictly speaking 'Zs at DB' or 'Zdb' are not correct terminology, much like 'ring main' instead of 'ring final circuit', everyone knows what is meant by it, it's commonly used, but it's not correct terminology.
But, 'Zs at DB1, 2, 3', whatever, is a statement...nothing wrong with the terminology, whatsoever.
 
Last edited:
But, 'Zs at DB1, 2, 3', whatever, is a statement...nothing wrong with the terminology, whatsoever.
I agree with ipf, but there will always be a Jobsworth that disagrees with this though.
 
Bit of Confusion there, Someone did tell me I have to do the Ze test with all Parallel paths even at origin seems a bit pointless.
You do your PEFC with all parallel paths connected at the origin not a ZE test .The Ze test determines the resistance of the earthing conductor external to the installation and confirms an earth connection to the installation hence it’s done with no parallel paths connected.
 
If it's the origin CUU does anything need to go into
"Zs at DB" on the "Schedule of test results" form ?
You do your PEFC with all parallel paths connected at the origin not a ZE test .The Ze test determines the resistance of the earthing conductor external to the installation and confirms an earth connection to the installation hence it’s done with no parallel paths connected.
I'm talking about Schedule of test result - Zs at DB
 
ill just take it you don't have to do Zs at DB at origin DB, unless anyone says differently.
The test carried out at the origin DB is the Ze not Zs. This is done with parallel paths removed to confirm the continuity and loop impedance of the DNO supply.

Zs is done with parallel paths in place on distribution and final circuits to ensure the installation disconnection times can be met.
 

Reply to Zs from board supplying another board in the Electrical Forum area at ElectriciansForums.net

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top