Taking cables from a house to a garage

[ianmacd]

Which you have agreed, the few inches of cable between the two is not going to make any difference from the electrical point of view.Did you read mu numeros posts about how I'm not debating the electrical aspects of it?

They're not going to be joined again.

Exactly so you have in no way connected that to the PEN.

So North America and Australia are in agreement.

Not necisserally even with eachother as ADS's post was unclear at to where the required rod needed connecting to just that it was on the clients side and US not with you as, by your own admission they have to connect to PEN at the service head so probably by the DNO equiv.

in RED.

 

[spinlondon]

Ian, Section 411.4 describes a TN system(I know its not allowed, but it is still described), where exactly does it state that the additional connection to earth must be made by the DNO?

Where does it state that the connection has to be made at a service head, and connot be made at the MET?

 

[ADS]

Ian, Section 411.4 describes a TN system(I know its not allowed, but it is still described), where exactly does it state that the additional connection to earth must be made by the DNO?Where does it state that the connection has to be made at a service head, and connot be made at the MET?

Sorry about this, Spin, but I can't let this false claim by others on here go on - TN systems are, of course, allowed.

Three main catagories:

IT

TT

TN

TN is broken down into sub catagories:

TN-C-S

TN-S

TN-C

TN-C is the system that is prohibited in the UK - due to the fact that you would be continuing the PEN conductor into the consumer side of the installation.

When BS7671 refers to a TN system it is referring to the three TN systems.

 

[SPECIAL LOCATION]

When BS7671 refers to a TN system it is referring to the three TN systems.

(just finish your example off there.... :Blushing )

As in the table of max disconnection times on page 46.. (Table 41.1)

"TN" systems

and "TT" systems

far left hand column!

 

[PBC_1966]

Did you read mu numeros posts about how I'm not debating the electrical aspects of it?.

Yes, but as I said earlier, is anyone going to try to argue that what you have done is somehow dangerous? (Other than Steptoe, that is.) Even if your interpretation of BS7671 not allowing it is correct, it doesn't alter the electrical facts on which we both seem to be in agreement.

Exactly so you have in no way connected that to the PEN.

Only if you ignore that big hunk of copper between the incoming supply and the MET. Who's to say whether you have the electrode connected to the PEN and the MET is there just to tap off the installation's earthing system, or whether you have the installation's earthing lead running to the PEN and the MET is there to tap off for the electrode conductor? Either and both. It makes no difference - They're all connected together.

Not necisserally even with eachother as ADS's post was unclear at to where the required rod needed connecting to just that it was on the clients side

Not certain, but I vaguely recall hearing something along the lines of the N & E busbars being bonded together at the main panel in Australia, so this would be the point at which they become separated. Maybe ADS will be able to confirm or correct and clarify on the precise point to which the electrode is connected.

US not with you as, by your own admission they have to connect to PEN at the service head so probably by the DNO equiv.

Not necessarily at the service head. As the NEC rule I quoted above states, the bond may be made anywhere up to and including the neutral bus or terminal at the service disconnecting means.

Typically the conductor will be run directly from the neutral bus at the main distribution panel (where the main panel is also the service disconnect, as is the norm in residential installations). Sometimes it's from the neutral at the meter base, although that's still generally part of the consumer's equipment, as is the feed into the meter (the utility co. just provides the meter itself and hooks up the power).

 

[ADS]

From AS/NZS 3000:2007 Ammended July 2009

Standards Australia - Rod connected to the earthing terminal - complete with link between the main neutral bar and the earthing terminal.

 

[ianmacd]

Ian, Section 411.4 describes a TN system(I know its not allowed, but it is still described), where exactly does it state that the additional connection to earth must be made by the DNO?Where does it state that the connection has to be made at a service head, and connot be made at the MET?

By refering to PE and PEN conductors. We would call them Main Earth (and refer to MET) and Neutral). Also uses the example at the point of entry into the building which will still be the DNO's side of the installation.

When I have been using TN I, of course, refer to the collective of TN-S, TN-C-S and TN-C so I do not understand your comment that its not allowed.

So what I am seeing is support for the argument that the rod should be on the PEN as it is in the overseas examples given. The argument that electrically its no different is flawed in that the PEN has been seperated and as we agrees will not be recombined.

I personally feel that our (UK's) implementation of TN-C-S is dangerous (obviously so do others as its not allowed for supply to caravan parks, pertol statiosn etc...) due to the lack of earth rod at or near point of entry into a premesis and connected directly to the PEN.

 

[spinlondon]

By refering to PE and PEN conductors. We would call them Main Earth (and refer to MET) and Neutral). Also uses the example at the point of entry into the building which will still be the DNO's side of the installation.

Not necessarily.

The point of entry to a building, can often be after the DNO's side of things. e.g. when the meter is placed in an outside cupboard.

 

[ianmacd]

Not necessarily.The point of entry to a building, can often be after the DNO's side of things. e.g. when the meter is placed in an outside cupboard.

Isn't it inside the cupboard then .

 

[spinlondon]

Isn't it inside the cupboard then .

Point of entry is usually considered to be inside the building.

See the requirements for equipotential bonding. "Shall be made as near as practicable to the point of entry of that service into the premises."

 

[ianmacd]

Point of entry is usually considered to be inside the building.See the requirements for equipotential bonding. "Shall be made as near as practicable to the point of entry of that service into the premises."

No idea why you have jumped to that wrong conclusion as premises is defined as land and property. Also a point is defined in BS7671 as a termination of fixed wiring, i.e. the cutout. So all that is saying is as close as possible to where the DNO's cable is terminated on the land (which is usually in or around a building).

 

[spinlondon]

Are you having a giggle?

Are you telling me that you bond at the property line, and not inside the premises?

 

[ianmacd]

If the meter was at the property line, wouldn't you be doing that to try and comply with 7671?

 

[spinlondon]

Not if it was down the end of the garden.

 

[ianmacd]

Not if it was down the end of the garden.

And you have a moan at people for not complying with BS7671 and you wouldn't yourself. Isn't that just double standards?

 

[spinlondon]

Ian the requirements for bonding extraneous-conductive-parts are that they be bonded as close as is practicable to where they enter the premises.

Now you are advocating that we bond as soon as the services cross the propertyline and enter the garden.

This forum doesn't half throw up some weird ideas.

Earth rods are lethal, and bonding must take place down the end of the garden.

 

[ianmacd]

Do you actually read other posts? I stated above that the word premesis refers to land as wellas buildings so that means as soon as the cable is on your land it is in the premesis. I think if you read the regulations properly too you will notice it actually states as close as possible ON THE CLIENT SIDE of any meters or stop taps.

 

[PBC_1966]

O.K., how about in this scenario we put a rod at the point where the power arrives on the land, then another at the other end of the feeder from the main panel in the house?

If it were my installation, that's what I'd be doing.

Can open, worms about to crawl out.....

 

[ianmacd]

Sounds good until the DNO refuse to connect it just because they can and then you have the issue of either not connecting it or connecting it for safety to the MET but not complying.

Would be far simpler just to get DNO to connect it to PEN or throw their unsafe earth away and just TT the installation.

 

[batty]

I really cannot see problem with TN-C-S its used by most dno and I have never heard of anybody being injured because of it. I will always use pme earth if available. To me its better than TT I have seen more unrealible earths due to TT than TN-C-S.