TT Supply for shed

[Welshsparky86]

hi everyone.

currently doing some farm work and require some guidance. i currently have a 16mm t+e overhead cable on a 300ma rcd, going to a CU in an outbuilding with a 30ma RCD main switch. I then have a 10mm SWA cable going to an animal shed, fed off a 32a mcb, protected by the rcd 30ma main switch. The armour of the swa is earthed at the supply end and not connected in the shed as it will be a TT system. I was told by a NICEIC inspector last year that there was nothing wrong with using the actual steel structure as means of earthing rather than earth rods, so I have taken a bond from the steel work in to the CU in the shed which supplies lights and sockets in there. Do i need another RCD in the shed to protect the circuits? Or does the one in the outbuilding suffice?

 

[uksparks]

Have you measured the Ra of the steel?

 

[TJ Anderson]

Yeah, steel work will prob give you an excellent Ra. Test and confirm. Re RCD, why add another if you already have the 30ma RCD Main Switch in outbuilding? They are already protected.

 

[uksparks]

Just to add, if it's iff a final circuit which is RCD protected to 30mA then there's no benefit in putting another one in.

 

[Welshsparky86]

Exactly my thoughts, a work mate disagreed with my logic so thought id check on here!
1st loop was 10 ohms but still a few girders to bond yet so can only get better!

While were at it, I have another issue! Got called to look at a job on another farm last week.
A nice new concrete base has been laid with galv poles everywhere for a cattle sorting pen. The farmer has brought 2 ducts from a shed to one of the galv poles hoping to put a socket somewhere close by to feed an electric cattle crush which comes with a 16A plug apparently. My issue is earthing, as I doubt any of the galv poles are bonded together. Suggestions?

 

[Leesparkykent]

Exactly my thoughts, a work mate disagreed with my logic so thought id check on here!
1st loop was 10 ohms but still a few girders to bond yet so can only get better!

While were at it, I have another issue! Got called to look at a job on another farm last week.
A nice new concrete base has been laid with galv poles everywhere for a cattle sorting pen. The farmer has brought 2 ducts from a shed to one of the galv poles hoping to put a socket somewhere close by to feed an electric cattle crush which comes with a 16A plug apparently. My issue is earthing, as I doubt any of the galv poles are bonded together. Suggestions?

How did u carry out this test?

 

[Welshsparky86]

It was a loop test off the incoming supply in the shed with earth lead of my loop tester connected to the brass nut and bolt which is bolted to the steel work. Should I be carrying out any other tests?

 

[uksparks]

That's probably all I would have done

 

[Welshsparky86]

Good! I was expecting a lashing there!ha! Any thoughts on my other issue?

 

[SPARTYKUS]

At the risk of extreme prejudice, wind up.

 

[Leesparkykent]

With main earthing conductor connected or disconnected?

 

[Welshsparky86]

The bond from the brass nut and bolt was disconnected from the shed's CU whilst testing

 

[davesparks]

Test it as you would an earth rod, I don't believe that farm wont have space for you to get the test electrodes placed at good distances.

your loop test is probably getting its reading via the bonding connections of everything else in the installation.

As for the design of the installation, well, I hope my learned friend Mr Spartykus at post #10 has hit a bullseye.

 

[Engineer54]

I literally switched off after reading about the 16mm T&E outbuilding submain being run overheard.

You can just guess what the rest of this farms electrical installation is going to be like...

 

[Welshsparky86]

Youre right. The state of the installation when I 1st got the call to go there was shocking. a lot has been done to improve it. The new shed with the swa feed underground is a good tidy job. As for the overhead, it was already there. Installed 10yrs ago. Obviously underground is a preferred method but can hardly make the customer change it. Maybe you should of switched off after reading "guidance" for all your comments worth

 

[Engineer54]

Youre right. The state of the installation when I 1st got the call to go there was shocking. a lot has been done to improve it. The new shed with the swa feed underground is a good tidy job. As for the overhead, it was already there. Installed 10yrs ago. Obviously underground is a preferred method but can hardly make the customer change it. Maybe you should of switched off after reading "guidance" for all your comments worth

Trying to have a dig are you son?? I commented on the installation not YOU. Now after reading your post 5, i'd be keeping gob firmly shut, you clearly have little to no idea of what you're doing on this farm....