superconducting T&E discovered

[plugwash]

Personally I would try and split the outbuldings up into two separate circuits from the house (maybe make both single phase circuits but on different phases?). This would eliminate the second crossing of the road, reduce the demand on any particular circuit and reduce the length of the longest circuit. BTW it is perfectly fine to cleat SWA to the outside of buidlings.

More detail on each of the boards (photos if possible) especially the main board in the house would be useful if you want advice on how best to make connections. It would also be good to know the size of connection from the garage to the cottage.

It would also be useful to have a list of what equipment you have in each outbuilding and what the buildings are used for. Is there any electricity supply to the barn at all?

securespark, why do you recommend changing the existing TN-C-S supply to TT ?

what's wrong with extending the earth conductor from the existing distribution board?

There are a couple of things you need to be aware of if you do use the PME earth for outbuildings.

Firstly if main bonding is needed in the outbuilding (it will be if there are pipes coming in from underground) you need to make sure your earth is up to main bonding standards. Assuming this is a fairly normal sized supply and you use 10mm or 16mm 3-core with a core as earth this shouldn't be a problem.

Secondly TN-C-S isn't reccomended for farm buildings because voltage gradiants in the earth can have a bad affect on livestock. I don't know if this is an issue for these particular buildings.

 

[SparkyTris]

all the pipes to the property are alkathene, plastic. they have brass fittings of course, but the pipes and even the main is plastic. how does this affect bonding?

also pls can you explain a bit more about Voltage gradients in the earth and livestock?

 

[JohnD]

Voltage Gradients and Livestock:

The earth (ground, mud) is somewhat conductive, but has much higher resistance than e.g. a piece of metal.

If you bang a metal spike into the ground, and put 240v through it, the voltage immediately adjacent to the spike will be at 240v compared to the general mass or the world as a whole. At *say) a metre from the spike it will have dropped to (say) 100v, and at (say) two metres from the spike the voltage might be zero

(the distances and voltages are examples only, it will depend on the mineral content of the mud, and how wet it is)

A cow might have a distance between front feet and back feet of two metres.

If it has one front foot adjacent to the spike, and one hind foot two metres away, it will (in the example above) have a PD of 240v between its two feet; therefore current will pass through its body and it might die.

People suffer much less than livestock in this way, since their feet are much closer together, and they are more likely to be wearing boots.

The current passing into the earth might not be a spike; it might be a water pipe, or a metal fence post, or a steel-framed building, or a buried cable that has been damaged. This is a factor that electricians working on agricultural installations have to be very aware of, and is less vital elsewhere.

Metal drinking troughs present an extreme risk, because of the intimate contact with the animal's wet mouth, and horses are at exceptional risk as they usually have metal shoes in intimate contact with the ground, and nailed directly into their feet.

 

[holmslaw]

..

 

[SparkyTris]

Untitled

• SparkyTris
• 1 Apr 2011
• 1

anyone know the accurate name for this (the big brown thing)?

 

[SparkyTris]

I plan to
select the most underused phase inside the big brown breaker thing I posted just now.

take 16mm2 tails from it to a 100A switchfuse which I will mount adjacent.

from the metalclad 100A switchfuse I will route 15 metres of 3-core 16mm2 SWA out to the adjacent shed.

In the shed, the SWA will terminate in a lockable steel box where I will mount 3 x 5-way 100A marshalling blocks (Line, Neutral & Earth).

These marshalling blocks will then supply:
a consumer unit in the shed they are in, located a few yards away. Ill get to it with meter tails.

and

a consumer unit in another shed. This shed is 10m away, and I plan to get there with another run of 16mm2 SWA.

Please comment on my plan!
I'm not too worried about strict adherence to the 16th edition, due to the extremely remote (offshore islands) location. But I am concerned about practical/safety aspect, and doing the job (fairly) well.

NB there are no livestock involved in the sheds, However there is a shower-room in one of them.
there is no gas or oil plumbing on the site.

all comments gratefully received.

 

[Taylortwocities]

Thats why cows lay down during thunderstorms they know about these things.

How about your monkeys. What do they do?

 

[ChrisRogers]

I plan to
select the most underused phase inside the big brown breaker thing I posted just now.

from the metalclad 100A switchfuse I will route 15 metres of 3-core 16mm2 SWA out to the adjacent shed.


all comments gratefully received.

Why not take out three phase? Seems a much more sensible idea and future proof. Cost difference between 3 and 4 core SWA is minimal

 

[ban-all-sheds]

anyone know the accurate name for this (the big brown thing)?

What does the 1st 60% of your user ID represent?

I'm not too worried about strict adherence to the 16th edition,

Does news travel slowly up there?

But I am concerned about practical/safety aspect, and doing the job (fairly) well.

Only "fairly" well?

all comments gratefully received.

It would be better to get someone in, ...You should use a competent person for the work, links below
In Scotland:
Individuals registered;
http://www.sbsa.gov.uk/register/ListAC.asp
Companies
http://www.sbsa.gov.uk/register/SearchRegCo.asp?T=Construction

 

[SparkyTris]

can't anyone do anything better than make fatuous remarks?

 

[ricicle]

That's a single pole moulded case circuit breaker, but the advice you have been given is spot on - you sound out of your depth I'm afraid.

 

[SparkyTris]

The trouble with getting someone in for this work is that "someone" costs too much. There is no "someone" on this island, and there hasnt been for years. So getting someone in means paying their travel and accommodation from mainland UK as well as their market rates for the work, which are too high anyway. No, don't argue with that. They are. I know it's not the tradesman's fault re overheads & regs and all the rest. The reason the "cowboy" market exists is because "professional" rates are too high.

Most of us out here have a modicum of incompetency in all trades, by necessity. Thats how it always has been and hopefully how it always will be. We're demonstrably not any more or less safe than anywhere else that has the dubious benefit of registered tradespersons & buildings inspectors.

regarding the SBSA registers, any idea how many of them there are up here? 1 firm, serving industrial sites and 1 individual, who is at sea half the time. So Thanks for that, but there's really no point in making these comments unless you fully understand the situation is there?

Why on earth am I asking questions here if I hadnt already decided to expedite this work myself?

 

[JohnD]

then maybe you are going to have to learn to do it properly.

Does that idea appeal?

 

[SparkyTris]

that is the general idea. learning, in this case, by doing.

 

[ban-all-sheds]

The reason the "cowboy" market exists is because "professional" rates are too high.

Would you fly in a plane piloted by a "cowboy" pilot?

Or use a "cowboy" dentist or doctor?