ok guys, we all know this forum is for all, some basic questions do get asked, but that is inevitable this being a forum. I would urge all posters to be honest regards competancy as this would help rid the forum of any remarks that can become personal.
Electricians who have been in the game for over 40 years will still learn if they are willing to acknowledge their limitations.
To the original question
Zs is the measured or calculated maximum earth loop to ensure that circuit protection is in place. The Zs should never be a problem with any rewire or new build because as circuit designer you have a duty to ensure that all cable calculations based on maximum demand are within the precribed limits.
This is one area where I would agree with other members who question the ability of DI's.
It would appear from some questions that very limited knowledge of electrical calculations are being asked from those who are or claim to be fully qualified.
I and the forum administrators are not interested in your abilities, this forum is for all, but we would ask that if a question is asked and you feel the urge to answer just give your answer without the remarks other forums adopt.
The main problem I see with any reply is that when it is posted in the open, few people will ask, and the results can be that those who need to ask will not, resulting in nothing being learned.
Another thought I would like to share is that we get a lot of visits from people who are not trained, who will look through posts and learn from them.
They may never post but your answers will help them pass exams, you may never get any thanks for this but you may be the one responsible for a single person eventually becoming a very good electrician.
I could ask Apache to go through old questions and we could all have a laugh at the basic question we may all have asked at one time or another, or we can carry on giving good advise and answer the question rather than question the Op.
We all learn, if we are honest we learn each and every day.
