sub main?

Talk Electrician Forum

Help Support Talk Electrician Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

musicspark

Senior Member
Joined
Mar 22, 2009
Messages
368
Reaction score
0
Hi chaps,

I visited a house the other day which has a granny flat. this is supplied by a 16mm T&E On a 50A Breaker with 30mA RCD from the CU in the house. There would not appear to be any extra earthing run along with the submain for the granny flat.

would i be right in thinking that the 6mm in the T&E is inadequate for the main earth between the two CUs?

Should I run a 10mm alongside the T&E?

 
If we do any sub mains in 16mm twin and earth we also run a seperate 16mm earth alongside.

I did some work on two flats a few weeks ago where all the flats are supplied by 16mm twin and earth with no additional earthing, not really very good practice and I am amazed they got away with doing it this way.

 
is there any main bonding is the granny flat? its own water supply?

 
is there any main bonding is the granny flat? its own water supply?
This is the key question for me, if there's no main bonding taken from the sub-main CU, what's the difference between this an a fixed load requiring 16mm cable - so long as Zs values are acceptable obviously.

 
kinda what I figured. I will have access to the granny flat later this week and will check the bonding situation

incidentally , can someone explain the adiabatic equation to me?

 
if there are no metallic services the T&E is fine, but if there are metallic services and you want to include the flat into the equipotential zone then a 10mm earth will be required

 
Top