electrical installation farm

[The apprentice]

Hi there iam about to start a new installation removing existing electrical equipment from a farm and renewing every board etc, inside the new distribution boards my question is would i have a 300mA RCD main switch there for outgoing circuits I.E sockets on a 30mA rcbo.? Also regulation 705.415.2.1 intended for live stock all supplementary bonding shall be connected to extraneous conductive parts sizing of supplementary bonding for this? thanks in advance dont really do farms first one i will do with my boss just want a bit knowledge and hope iam not being stupid asking these questions

 

[Strima]

You only need to protect livestock where livestock might be present. So within office/accommodation areas you only need to provide additional protection as per the book.

Farms can be notoriously difficult to design due to their completely random layouts and multiple uses of buildings. They key is to get your distribution circuits right the first time and add plenty of room for future expansion.

Farmers will quite happily add loads to their installation without a second thought then blame you when the whole lot falls over just at the wrong time.

 

[The apprentice]

You only need to protect livestock where livestock might be present. So within office/accommodation areas you only need to provide additional protection as per the book.

Farms can be notoriously difficult to design due to their completely random layouts and multiple uses of buildings. They key is to get your distribution circuits right the first time and add plenty of room for future expansion.

Farmers will quite happily add loads to their installation without a second thought then blame you when the whole lot falls over just at the wrong time.

total agree with that mate hear alot about farmers as for office/accommodation there is none on this install just farm land there is a shed with a lot of live stock in a farm shed which will need bonding because they can actually touch the metal work

 

[timhoward]

Also regulation 705.415.2.1 intended for live stock all supplementary bonding shall be connected to extraneous conductive parts sizing of supplementary bonding for this?

To check you caught the point - that bit is about connecting exposed and extraneous conductive parts together in areas that can be touched by livestock.
Regarding the size, see section 544.2.2 - you will see why a one size fits all answer isn't possible!

 

[cliffed]

Hi there iam about to start a new installation removing existing electrical equipment from a farm and renewing every board etc, inside the new distribution boards my question is would i have a 300mA RCD main switch there for outgoing circuits I.E sockets on a 30mA rcbo.? Also regulation 705.415.2.1 intended for live stock all supplementary bonding shall be connected to extraneous conductive parts sizing of supplementary bonding for this? thanks in advance dont really do farms first one i will do with my boss just want a bit knowledge and hope iam not being stupid asking these questions

Time delay Rcd upfront

 

[The apprentice]

To check you caught the point - that bit is about connecting exposed and extraneous conductive parts together in areas that can be touched by livestock.
Regarding the size, see section 544.2.2 - you will see why a one size fits all answer isn't possible!

thanks mate will read up that thank you

 

[pc1966]

Section 705 has most details.

As above, most areas will need a 100mA or 300mA delay RCD as part of fire protection.

Also note the extra bonding, earth mats, etc, in any areas with livestock and special needs if the supply is PME (TN-C-S). In that case (even for TN-S in case it is "upgraded" to TN-C-S) you might find it simpler to TT the installation with the up-front delay RCDs along with RCBOs for selectivity and adequate earth rods, the usual spec is 167 ohm for 300mA but aim for under quarter that as you want no more than 25V at disconnection and margin for drought/frost taking the top 0.5-1m of rod out of commission.

Also remember rats! A sparky I know who does a lot of farm work swears by Flexishield cable for most stuff that does not merit SWA. It is tough, UV resistant, gland with simple IP68 plastic things, and looks fairly smart (stays in place better than H07RN-F, your next type to try). They even do a cat-urine flavoured version for really desperate rat problems:

Flexishield R How It Works

Flexishield R How It Works

www.flexcables.co.uk

 

[pc1966]

OK, I don't see any reference to 25V for agriculture in a quick scan of section 705 but I'm sure somewhere in the past I saw that as the limit for livestock areas. Or am I just gibbering?

 

[The apprentice]

OK, I don't see any reference to 25V for agriculture in a quick scan of section 705 but I'm sure somewhere in the past I saw that as the limit for livestock areas. Or am I just gibbering?

never seen that either

 

[timhoward]

OK, I don't see any reference to 25V for agriculture in a quick scan of section 705 but I'm sure somewhere in the past I saw that as the limit for livestock areas. Or am I just gibbering?

You were certainly right once! It was in 16th edition and I think removed in 17th.
( a trip down memory lane
TLC Electrical Supplies - https://www.tlc-direct.co.uk/Book/7.6.2.htm )
I think it's just Medical locations that have a different 25v touch voltage in 18th?

 

[pc1966]

Ah, I thought so!

Must have rubberised cows these days to double the limit...

 

[The apprentice]

the resistance in a cow with the water would be fetal

 

[brianmoooore]

Cows are extremely sensitive to stray voltage. Had a milking parlour a few years ago where the bonding between the metal the cows stand on and the metal where they place their necks to feed had gone AWOL.
There was a fault elsewhere on the farm putting a small voltage on the earth wire, and the cows made it abundantly clear they didn't appreciate this voltage across their bodies. They refused to be milked, lashing out with their hooves, and the place looked like an explosion in a sewage works.
As for rats, they will attack any cable that gets marginally in their way. Route all cables under joists and beams where they cross them, never over the top, and run cables low down on the side when they run along joists.

 

[loz2754]

And of course not forgetting that ALL switchgear, consumer units, and accessories must be at least IP44.

 

[pc1966]

Cows are extremely sensitive to stray voltage.

Lets face it, for the farm animals it is like a shower area as all naked and damp!