Supply and final circuits for stables.

[Schegg]

Hi all, just looking for advice prior to a potential upcoming project supply stables for horses.

The supply characteristics into the main house is TNCS and the stables are located approx 40m away from the building.

I am thinking of putting a 1w non-rcd protected consumer unit at supply end, running a 10mm SWA (25a supply) to stable end terminating into a 2way 30mA rcd main switch consumer unit to provide power and lighting arrangements.
I understand equipment needs to be IP44 and containment needs to be protected from damage so will be using weatherproof switching/socket outlets etc and installed in conduit. All sockets/switching are external to the stables and not inside, however the lighting will be inside.. obviously!

Would it be required/good idea given the the detached stables also be protected by a TT system? This is where it gets a bit confusing..

Any advice greatly appreciated (hopefully not too much criticism), little bit tricky for this little brain of mine!

Thanks

 

[bill01803]

See 705.411.4

 

[buzzlightyear]

Any water near the stables like metal .
you can export the earth providing has above .

 

[buzzlightyear]

https://electrical.------.org/media...tdoors-a-supply-to-a-detached-outbuilding.pdf

 

[Wilko]

If extending supply on farm outbuildings I normally use TT. Check out reg 705.415.2.1 and it's footnote re using PME where animals are involved.
Also, when an outbuilding is on a residential plot it may still be considered domestic and Part P applicable, just saying.

 

[Welchyboy1]

Just an additional thought, not a requirement as im aware, but i protected sockets that were used for hair clippers or in close vicinity to horses etc via 10mA
Rcd

But these were for £30k racehorses

 

[JD6400]

Hi schegg , although not agricultural in as much as cows or pigs , I would say it is a thin argument to class a stable as anything else. After all you can still eat horse , a lot of people proberbly still do after a good staturday night out , even if not aware of it !

If fed from a domestic property , it at least used to be part P applicable , and I suspect still is.

You do need to tt the stable and I would also tt the sub main with an s type up front.

Also unless you are only looking at one or two stables and a tackroom , I would recommend a bigger supply than 25 amp.

 

[buzzlightyear]

Read guidence note 8 .
Sub main out TT the system job done. .

 

[davesparks]

You do need to tt the stable and I would also tt the sub main with an s type up front.

What is your thinking behind installing a TT system for the submain?
This seems like a difficult thing to do safely for no real gain to me. To do it safely you would need to ensure that the two earthing systems are completely isolated from each other and nothing connected to the TT earth is exposed to touch within the TNCS installation. So you would have to install an insulated switch fuse, ensure the SWA gland can't become exposed etc.

 

[Deleted member 26818]

SWA from a non RCD protected source to the stable.
TT at the stable.
Only thing that concerns me, is protecting the external sockets and switches from damage.

 

[buzzlightyear]

Basic requirements for earthing and bonding
Where an installation serves more than one building, main protective bonding is required in each building served, except for a building where there are no extraneous-conductive-parts, such as metallic water, gas or oil installation pipes (Regulation 411.3.1.2 refers).

Option 1: Extending the earthing and bonding system

The image shows an example of the earthing and bonding arrangements where the installation in a house is extended to serve a detached outbuilding. A Building Earth Marshalling Terminal (BEMT) is usually provided in the outbuilding to marshal together the main bonding conductor(s), if any, and the circuit protective conductors (cpcs) in that building. The BEMT must be connected to the MET by:

• the cpc of the distribution circuit supplying the outbuilding, and

• a main bonding conductor, if there are any extraneous-conductive-parts at the outbuilding.

As shown, the functions of the cpc and main bonding conductor (if any) may be combined in a single protective conductor having a cross sectional area (csa) meeting the requirements for both functions.



Option 2: Making the installation in the detached outbuilding part of a TT system with its own installation earth electrode and MET

The image shows an example of the earthing and bonding arrangements where an installation in a house supplies an installation in a detached outbuilding, forming part of a TT system with its own installation earth electrode and MET. It is desirable for there to be no connection between the earthing and bonding arrangement of the installation in the outbuilding and that of the installation in the house (such as through a protective conductor or shared metallic pipeline), as shown.

Note: Although both options show an earthing facility provided by the distributor being used as the means of earthing (TN-S or TN-C-S system), the earthing conductor could be connected to an installation earth electrode instead (TT system).



Table 1 – Sizing requirements for cpc and main bonding conductor

Note. The requirements of Regulation 544.1.1, referred to in Table 1, can result in a main bonding conductor size greater than that of the live conductors or cpc of the distribution circuit supplying the outbuilding, particularly where PME conditions apply (TN-C-S system).

Table 1 summarises the requirements of BS 7671 for sizing the cpc and main bonding conductor to the outbuilding. If the functions of these two conductors are combined in a single protective conductor, this must have a csa not less than that required for either function. Where there is no such connection, the main requirements of BS 7671 applying to the earthing and bonding are as summarised in Table 2.



Table 2 – Requirements where the outbuilding installation forms part of TT system with no connection to the earthing and bonding arrangements of the house installation:

A further consideration applies where there is a connection between the earthing and bonding arrangement of the detached outbuilding and that of the installation in the house, if the latter installation forms part of a TN-C-S system where PME conditions apply.

Where this is the case, PME diverted neutral current may flow in the connection between the two earthing and bonding systems. To avoid harmful thermal effects caused by this current, the csa of this connection and of the main bonding conductors and the earthing conductor of the installation in the outbuilding needs to meet with the requirements for a main bonding conductor of the installation in the house (which are summarised in Table 1).

 

[buzzlightyear]

the best thing to do is copy and paste it to your pc or lap top ,above .

 

[R-fur]

Keep the lights as high as poss as horses will lick, bite anything. I keep the wiring out of reach of the horses and ideally use double pole switching so that the fitting is completely isolated when switched off. I also use pull switches up out of the way, with a cord just long enough to reach.