DIY Doctor

what type of wiring system do I have

Postby eddie » Sat Sep 15, 2007 11:16 am

My house electric supply is fed from an overhead line cable with 2 cores, what type of system is this? TT, TNS TNC or what.

It has no in coming earth as such so as I understand I'll have to run a 16mm earth from earth bar in comsumer unit to an earth rod and 2 x 10mm earths to my water & gas.

any help cheers
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Simply Build It

Postby Add » Sun Sep 16, 2007 8:18 am


You have a TT system. Your whole consumer unit must be protected by an RCD. 16mm to the earth rod 10mm to the gas and water also sound right. Remember limitations under part P.

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Postby cm » Sun Sep 16, 2007 6:18 pm

Last edited by cm on Sun Sep 16, 2007 8:26 pm, edited 1 time in total.
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Postby sparx » Sun Sep 16, 2007 6:54 pm

Hi if you are using an earth rod then it must read lower than 100 Ohms to fully comply with all requirements, & must also cover ALL circuits not just power!
standard best-practice is to change main sw. for time delayed 'S' type RCD, idealy of 100mA rating to give tripping discrimination. Cheaper/easier way may to ask supply company to provide earth from Neutral block instead of rod which would not require any RCD changes, most overhead systems work this way & would become PME/TN-C-S.
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