pme earthing

[blackie007]

can i take pme earthing outside of a commercial building to supply some containers or am i right in thinking its treated as the same as domestic and i only take live and neutral out and put an earth rod in local to my new supply?

 

[ashrow]

Whats wrong with taking a pme earthing from a domestic ?
Only asking as it seems you need to do some research !
Others may come across and help but as a first post it does not come across to well (introduce yourself, say hi and if you are studying, learning or asking a home work question) it helps us help you

 

[blackie007]

hi im graham and im 20,as far as ive been told and learnt at college you are not allowed to take pme earthing outside of its origin,not to a shed ect ect,but i need to take a supply to two metal containers from a work shop,in swa cable,but im led to believe that i cant take the earth from the work shop i have to put an earth rod in at the container end? is that right or is someone pulling my chain?

 

[telectrix]

pulling your chain, mate. it's a myth that you can't use the pme for your outbuildings.

 

[ashrow]

No one is "pulling your chain"
From my understanding you can run a feed to your out buildings from your pme supply as long as certain things are met

do you know of these ?

 

[blackie007]

im trying like **** to scrammble through the regs book and as yet i havent found my answer,so are you saying that i can take the earth outside the the work shop and ive no need to put an earth stake stake in? regards graham

 

[ashrow]

Yep

if there are water or gas services to those containers then you need to do some research (i cant give you all the answers but i am sure if you searched these forums you would learn more)

 

[blackie007]

thanks bud

 

[KFH]

If there are services in the outbuilding then they need to be bonded according to the regs which can mean a large bonding conductor so it becomes more economical to TT the outbuilding.

Edit - Apart from any issues about different earth potentials and lost neutrals etc.

 

[blackie007]

there are no services just 3 phase machinery,would it not be safer just to drop the earth from the work shop and earth rod at the containers anyway? thank you for your help

 

[Engineer54]

As these buildings are steel containers, you will need to bond them to the workshops MET. No reason why you can't extend the equiptential zone, and retain TN Zs values that you will almost certainly loose by TT'ing.

Personally i would use the PME but also drive a rod (2 X 5/8'' coupled) or two as well, and connect to the new DB's EMT. In my opinion, all PME/TNC-S supplies should have a local rod connected to the installations MET, but not one with an unstable numbty 200 ohm Ra or thereabouts.... lol!!

And NO it wouldn't be safer dropping the earth and having to rely on a rod and a single RCD.... Not when you can have a TN earth with additional RCD protection....

 

[GLENNSPARK]

can i take pme earthing outside of a commercial building to supply some containers or am i right in thinking its treated as the same as domestic and i only take live and neutral out and put an earth rod in local to my new supply?

stop daydreamin......start understandin that a TN earthin arrangament is beneficial.....(unless livestock or the very real possibility exists of neutral loss exists).....extendin or exportin a PME is good.....