tt or not tt?

[paul b b]

hello guys.

I was looking at my mum and dads old fuse box with a view to change it. now i could not work out what system it was. there are over head cables but there is only 1 cable not 2.

i can see a earth cable going through the wall but cant work out where it goes.

if it is upgraded from a tt would it be to a TN-S or TN-C-S?

is there a easy way of working out what type of supply people have?

thanks

paul

 

[Andy™]

chances are TT. get a test kit onto the earth and prove it. you will never get TNS on overhead, but it may have been upgraded to TNCS at some point. but unless the earth cable leaves the service head or the sheath, then its almost guaranteed to be TT

 

[paul b b]

sorry to sound like a idiot here.

if i look up at the outside cable and see 2 cables goint to the house then its a tt.

if it is 1 cable then tncs and testing it would confirm that.

many thanks

 

[Andy™]

the incoming supply will always have 2 conductors - phase and neutral. if the earth is split from neutral, its TNCS. this will be done at service head. if ifs elsewhere, its TT

and pics would be good

 

[paul b b]

ok will take pics next time i am there

 

[aptsys]

chances are TT. get a test kit onto the earth and prove it. you will never get TNS on overhead, but it may have been upgraded to TNCS at some point. but unless the earth cable leaves the service head or the sheath, then its almost guaranteed to be TT

There is TN-S in some areas on overhead cables, but they're slowly getting removed by the DNO. Neutral is still at the bottom, then earth, then the three phases. I was chatting to one of the guys removing it recently from Cowbit in Lincs, now converted to TN-C-S, but still exists elsewhere.

 

[Andy™]

There is TN-S in some areas on overhead cables, but they're slowly getting removed by the DNO. Neutral is still at the bottom, then earth, then the three phases. I was chatting to one of the guys removing it recently from Cowbit in Lincs, now converted to TN-C-S, but still exists elsewhere.

no. if you have 5 overhead lines, the second bottom is smaller CSA than the rest. thats because its a switched live for street lights.

 

[binky]

hello guys.I was looking at my mum and dads old fuse box with a view to change it. now i could not work out what system it was. there are over head cables but there is only 1 cable not 2.

paul

Split concentric sometimes used, especially when looping from one property to another. If in doubt TT it anyway, you only need use L & N from supplier whether it be TN-s or TN-C-S

 

[aptsys]

no. if you have 5 overhead lines, the second bottom is smaller CSA than the rest. thats because its a switched live for street lights.

Not what the DNO guy said. There were triple drops to every house also including from this 5th conductor ?:|

 

[Andy™]

first time i heard of that. seperate overhead earth sounds very bad