AGRICULTURAL: TN-C-S extension or TT

[Ryan Lee]

Hi, forgive me if this thread isn't where it belongs.

I would like the gather some alternative views on earthing systems and which one would be correct for agricultural premises.

It is to my current understanding that where livestock are present an earth stake should be used.

Can TN-C-S be extended from the distribution board to another consumer unit, and then onto another one again?

Also, when is it ok to use SWA sheaving as a main earth, and when is it not?

many thanks

 

[jackhammerJIM]

RYAN

do you own a copy of the wiring regs ?

 

[Deleted member 9648]

Section 705 covers agricultural installs.
Using the SWA sheath as a cpc depends on it's CSA in relation to the size of the copper cores.If you do a search there are numerous threads on this,and you will find tables with SWA sizes in a simple go-no go format.

 

[PEG]

Also,fella,there are reasons why you need to keep livestock and earth stakes apart...search for earth rod pits,potential change,distance between beasts legs etc...loads of fun,nowt rude,honest

 

[Engineer54]

Also,fella,there are reasons you need to keep livestock and earth stakes apart...search for earth rod pits,potential change,distance between beasts legs etc...loads of fun,nowt rude,honest

Not quite sure what you're meaning is here?? A building that will be used to accommodate livestock, it is preferred that the electrical earthing system be made TT where TNC-S is the incoming supply to the farm. That's not to say that TNC-S is prohibited, it can be used where the concrete flooring of livestock housing buildings, incorporates a main bonded metal metal grid.

OP... You can extend the equipotential zone of a PME system providing you meet the requirements.
As for the armouring of SWA cables, the CSA of the steel wires will be of a sufficient size to comply as the CPC, up to 95mm. However if any main bonding is required at the load end of the submain, the SWA CPC will ''NOT'' comply and will need either an extra core in the SWA cable or a separate suitably sized earthing conductor to be run in with the SWA cable,

 

[GLENNSPARK]

here:

http://www.earthingnuts.co.uk/pdf/pvc_xlpe.pdf

 

[Engineer54]

here:

http://www.earthingnuts.co.uk/pdf/pvc_xlpe.pdf

Jesus .... how many more times, ....Throw that heap of crap table in the bin where should have been yonks ago!!!!

 

[Engineer54]

Blue = min CSA of cables SWA to comply.

(Red) = Cable does not comply.

Note: These tables relate to Complance for CPC purposes Only, and ''NOT'' for Main Bonding.

Table for 70[SUP]0[/SUP]C Thermoplastic PVC SWA cables.

Conductor CSA​	Minimum CSA of SWA to meet 54G​	CSA of armour 2 core​	CSA of armour 3 core​	CSA of armour 4 core​
1.5​	3.4​	15​	16​	17​
2.5​	5.7​	17​	19​	20​
4​	9.0​	21​	23​	35​
6​	13.6​	24​	36​	40​
10​	22.6​	41​	44​	49​
16​	36.1​	46​	50​	72​
25​	36.1​	60​	66​	76​
35​	36.1​	66​	74​	84​
50​	56.4​	74​	84​	122​
70​	79.0​	84​	119​	138​
95​	107.2​	122​	138​	160​
120​	135.3​	(131) ​	150​	220​
150​	169.2​	(144) ​	211​	240​
185​	208.6​	(201) ​	230​	265​
240​	270.6​	(225) ​	(260)​	299​
300​	338.3​	(250) ​	(289)​	(333)​
400​	403.9​	(279) ​	(319)​	467​

Table for 90[SUP]0[/SUP]C Thermosetting SWA cables operating at 70[SUP]0[/SUP]C.

Conductor CSA​	Minimum CSA of SWA to meet 54G​	CSA of armour 2 core​	CSA of armour 3 core​	CSA of armour 4 core​
1.5​	3.4​	16​	17​	18​
2.5​	5.7​	17​	19​	20​
4​	9.0​	19​	21​	23​
6​	13.6​	22​	23​	36​
10​	22.6​	26​	39​	43​
16​	36.1​	41​	44​	49​
25​	36.1​	42​	62​	70​
35​	36.1​	62​	70​	80​
50​	56.4​	68​	78​	90​
70​	79.0​	80​	90​	131​
95​	107.2​	113​	128​	147​
120​	135.3​	(125) ​	141​	206​
150​	169.2​	(138)​	201​	230​
185​	208.6​	(191) ​	220​	255​
240​	270.6​	(215) ​	(250)​	289​
300​	338.3​	(235) ​	(269)​	(319)​
400​	451.0​	(265) ​	(304)​	452​