Tt/tns ?

[stidge]

hi all,been to cottage today being refurbed.overhead cables come to old metal JB/isolator on outside wall feeding 3 cottages.From what i can gather then there is an armoured coming from that underground to another metal JB/Isolator. Next door has a 10mm cpc crimped to the metal box,mine has a 6mm cpc crimped also.I have taken a ELI test at mains and it read 9.68 ohms.Obviously im rewiring,new board,earthing etc.Is the best way to fit a front end RCD(100ma or 30 ma ?)and put a new earth spike in and upgrade the original TNs cpc to 16mm ?.Do i fit an 100ma isolator and a 30ma dual RCD board or just a 100ma isol and a non RCD CU ? All advice,comments will be a great help thanks,have never had to install an earth rod yet believe it or not!!

 

[nickblake]

Firstly im totally confused here , what earthing system do you have ,TT or TNS as you mention that its TNS , but judging by the readings its TT ,if the install is that old i would contact the DNO to ensure that the supply installation is safe , you have not mentioned any meters before i commit to any advice a picture may be an idea , whats an ELI test do you mean a Ze test max is , TNCS 0.35 ,TNS 0.8 TT <200 ohms

Nick

 

[stidge]

yes nick its an overhead supply to on box feeding several cottages,from here there is a large SWA feeding three other cottages run underground,the earth is crimped to said box .I am thinking up[grade the earth that is crimped to box,30ma dual rcd board and install an earth rod ? thanks

 

[cs97]

Id be very suprised if the supply authority really understand the system provided here. If i was you id put a new rod in ensuring its less than 200 ohms and fit a split load board 2 30ma rcds seperating the new circuits. Check the psc reading to though. Have to be very careful with tt systems. Like the puppy that wont drown of the supply world.