Exporting PME to garage

[peteelecs]

Please canyou help I am a bit confused about the earthing to a shed if the house is PME can I just run an earth from the MET to the shed or can I only do this if house is TNS.How do i get earth to shed if its PME hope this doesnt sound to confusing any suggestions would be appreciated

 

[WDMDL]

No difference between TN-S and TN-C-S (PME) once it's in the house in that respect. Separate neutral and earth once you're past the service head, whatever the supply may be.

Simon.

 

[SimpleSimon]

You could just run a separate earth conductor from your main MET to the distribution board in the shed. 16mm

 

[trebor]

PME earthing should only be exported to buildings that are suitable as a seperate equipotential zone, if the building is suitable then an equipotential bonding conductor must be run equal to or larger csa to the one in the house and in any case a minimum of 10mmsq

Risks associated with sheds/garages are wet concrete floors and perhaps external metal cladding, for these reasons it is usual to create a segregated TT installation in the shed/garage,

PME can be used for earthing the sub main which is then segregated from the TT installation either by cutting back the armour or terminating in an insulated box, if you use this method the CCU in the garage must be all insulated

 

[High Tower]

Seperate the two systems, divorce the Earth. Earth the supply cable if it's Swa from the house side but then TT the shed.

 

[High Tower]

Trebor beat me too it

 

[kung]

Yep as said TT it ! didnt think the DNO would allow PME to be exported anyway because if they drop a neutral its a bigger risk so TT is the best option

 

[sparks1234]

so, what would you do if the garage is attached?, would you only make it a TT over say 10 mtrs? its a bit awkward to get a difinative answer on this

 

[Deleted member 9648]

For the Zillionth trillionth time there are no regulations preventing the TNCS earthing system being used for an outbuilding.If there are extraneous conductive parts in the outbuilding requiring main bonding then you must run that bonding back to the MET,which means a TT is more sense....if there are no parts requiring main bonding then use the TNCS earth as for any other install....or if you prefer waste your time and money providing a totally unecessary separated earth.

 

[kung]

if the garage is attached id keep it PME if detached i always TT its just something i always do buddy

 

[kung]

But everyone isnt as key'd up on the regs such as joe blogs and doesnt know about bonding do they ? just a thought if you TT then their cover'd either way just in case thay add something to the structure !

 

[Deleted member 9648]

if the garage is attached id keep it PME if detached i always TT its just something i always do buddy

Thats your choice........but there is nothing in the BRB preventing the use of a TNCS for an ordinary outbuilding,that should be made clear.

 

[IQ Electrical]

For the Zillionth trillionth time there are no regulations preventing the TNCS earthing system being used for an outbuilding.If there are extraneous conductive parts in the outbuilding requiring main bonding then you must run that bonding back to the MET,which means a TT is more sense....if there are no parts requiring main bonding then use the TNCS earth as for any other install....or if you prefer waste your time and money providing a totally unecessary separated earth.

Unusual to get the correct 'exporting pme' answer in just 9 posts

 

[Deleted member 9648]

But everyone isnt as key'd up on the regs such as joe blogs and doesnt know about bonding do they ? just a thought if you TT then their cover'd either way just in case thay add something to the structure !

cant see the relevance.....the 'added' extraneous conductive part would need bonding even if it was TT....just the method of bonding would be different.

 

[kung]

For the Zillionth trillionth time there are no regulations preventing the TNCS earthing system being used for an outbuilding.If there are extraneous conductive parts in the outbuilding requiring main bonding then you must run that bonding back to the MET,which means a TT is more sense.

I know theres no requirements of TT in the brb its what i always do as said its personal pref only although the DNO might have a different view !