Discuss TT help needed!!! in the Industrial Electrician Talk area at ElectriciansForums.net

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I have a question about TT systems, i have just done a rewire on a bungalow, and have installed an earth rod, all readings are good, have installed a high integrity 17th edition board, single rcbo for smoke alarms then split 30ma dual rcd for rest of bungalow, i think that is all you need to do, am i right to say that due to every circuit being protected by 30ma rcd i do not need to oversee the main incomer on a 100ma time delay.

Replies appreciated.

You are right,if you were installing a metaclad board then you would have to install an RCD on tails to board.As you are using a high integrity board then you dont need to as you already have 30ma protection on all circs.
 
Why do you need 100A Time delay on the tails to a distribution board? I thought if the board was fully protected by RCD and RCBO's the 100A breaker would never trip before them.

Is it to protect any metallic parts of the board becoming dangerous? Does a high integrity board have no metallic parts?

Sorry for been so dumb :eek:
 
i think he is concerned asbout covering the requirement to have a TT system to be protected by a 100mA time delay RCD

i would suggest installing the 100mA time delay RCD to comply, as although in practice it is highly unlikely each circuit could in theory have a leakage of 20mA, no RCD's will trip yet there could be 240mA running through earth in a 12 way CU.

Eskimo, my apologies if i was rude, i assumed you were making a response to something said in another thread.
 
Don't worry about it. I just really was curious. I have been having a good read up on ohms law this morning. Have found 2 different charts. 1 a triangle with V,I,R and the other a circle with P,I,V,R. Not sure what the difference is but it is certainly interesting reading.
 
Beaver74 I am only on the first year of a three year course.

As stated in the post "Ohms law is our third module starting in January and was just curious as to how I could use it" As I am sure some of you will be aware there are 9 modules alone in our first year before they allow us on to NVQ 2 & 3.

The comment in question to uksel was of genuine interest. I joined this forum for support and (hopefully) guidance..

eskimo39 i was'nt being rude i was just statting that ohms law in my apinion should be one of the first thing to learn as almost every thing revolves around this in some way
and i did miss read the 3 years
 

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