DIY electrical repairs in outbuilding and part P

[Simon]

Hello -

A relative has a small outbuilding that needs a general overhaul of its electrical wiring, and I'm wondering if it could be DIY'd without coming under Part P.

It's basically a small steel-framed barn that houses a couple of cars and a couple of horses. There's no wiring in the horses' part. It's fed by a short buried cable from the consumer unit in the house, which feeds a smaller consumer unit in the barn. Things which need to be addressed include:

- Most of the sockets and switches are old, some are cracked. Some may be exposed to rain during severe weather.

- A family of swifts has built a nest on top of the barn's consumer unit, which needs to be replaced.

- Presumably the earthing requirements need to be looked at, particularly in view of the amount of earthed steel around.

- I want to fix whatever needs fixing, but this would just be a repair operation, not a sneaky extension or enhancement.

I have done lesser electrical tasks before, I have a physics/electronics background, and am prepared to buy specialised testing kit. If I read up on all the regulations and best practice, is this legitimately DIYable without falling foul of Part P?

[Andrew Gabriel]

No. All such wiring comes under Part P. It's a separate question if you can self-certify or not though.

This is a very important issue, much more so because of the horses. Tiny leakage currents which humans can barely feel are fatal to most livestock including horses, so this has to be got right. For this reason I strongly suggest you get the work done by an electrician who is familiar with supplies around farm livestock. There are issues here which domestic electricians are unlikely to be very familiar with.

[The Medway Handyman]

Really? I didn't know that. What about electric fences for example?

I would have guessed that horses & cattle could have taken larger shocks than humans because of thier greater mass. How does that work?

Just a thought.

[Guy King]

The message from "The Medway Handyman" contains these words:

The problem comes from the greater wheelbase on a horse. What may be a trivial potential gradient for a biped can knock off a quadruped quite easily. This is why lightning rod terminals are buried a foot or so down

- keeps the surface potential gradient down.

[Andrew Gabriel]

An electric fence is pulsed, and the animal has a choice to move away from it. A leak from mains generally isn't pulsed. It will create a potential difference across the ground where it's earthed and the animal can't decide to let go of the ground and may not have the knowledge or be too confined to move away.

No, it's the opposite. In addition to the large wheelbase problem which Guy mentions, it only needs a volt or two across that to kill large animals, whereas a human would never have any concern about touching the terminals of a 1.5V battery, or even a 12V battery. This first showed up when a field of dead animals was occasionally found with no explanation being obvious. It has then been found that an insulator on an overhead wire is leaking tiny amounts down the support pole, generating a small potential difference across the ground not even noticable by humans, but fatal to the livestock.

Someone on this newsgroup was involved with litigation resulting from death of a horse due to earth leakage creating a small ground potential, but I can't recall who it was.

[David Hansen]

On Tue, 12 Dec 2006 00:52:24 GMT someone who may be "The Medway Handyman" wrote this:-

In addition to what has been said, in a four legged animal the current flowing between the front and back legs passes along the main nervous system and thus may disrupt it. A human standing up will not be affected by the potential gradient.

[Richard]

[The Medway Handyman]

Thanks chaps - I am a wiser man. How fascinating.

[tinnews]

I think the major issue is simply that horses and cows are *longer* than people so even quite small leakage currents into the ground will cause a large enough voltage gradient to affect them whereas it won't affect bipeds.

[Peter Crosland]

It clearly needs doing in a competent manner by someone fully familiar with Part P. The cost of getting done professionally will be much less than buying test gear for a one off job particularly when you add the cost of certification.. When the building comes up for sale your relative will be asked if all work has had the proper authorisation.

Peter Crosland

[jethro_uk]

Apparently it's not unusual to find a field of dead cattle, where lightning has struck the ground and caused a (bovine) fatal pd across the heart.

[Dave Plowman (News)]

Seems to me it's rather the opposite - it needs a specialist in wiring where livestock is involved.

The economic way would be to get it checked and certificated at the same time. Test equipment is needed really just to show up any faults - with decent workmanship and the correct proceeders followed there won't be any.

So what? It won't cost anymore to have done later - if indeed such a thing is asked for.

The idea of doing anything *just* with a view to re-sell is one of these things the TV makeover progs have a lot to answer for...