assessment on garage installation

[darren1981]

Hi guys.

I am in the process of applying for eleca registration and I am planning to wire my new detached garage up.
I know this seems to be a common question but there are so many answers out there I thought it would be helpful for me to start from the beginning . My supply is pme aburied underground via a existing power to the garage via a 2.5mm 3 core swa cable which supplied the old shed that I removed this is burried under ground to the house cu and connected to a 20a rcbo.
but it relied on the 3rd core and armor for earth which is not to regs.
my first questions is can i use this existing cable and install a tt earthing system for the garage I've work out that after v drop the cable will take 26amps and the cable has been tested and shows no sign of any problems .
2nd if that comply s and I can get a good test result from a earth rod (or 2) terminate the swa in a plastic main switch housing commenting the 3rd core and armour together and connecting L&N through it to a 2 way cu with a rcd 1x 16 a powerful circuit (2 socket outlets ) and 1x 6 a lighting (4 florescent luminaries) the garage has no gas or water pipes and I will be bonding and extreneous conductive parts.
Dose this sound right thanks in advance for and help and advic

 

[edrobbo8]

If you get a copy of this month's Professional Electrician magazine, there is a good article in there on exporting PME and running supplies to outbuildings. Pick one up in your wholsesaler, it's free!

 

[R G]

Don't know about Elecsa , but the NIC don't count work on you're own property...

 

[TJ Anderson]

.
but it relied on the 3rd core and armor for earth which is not to regs.

Nothing wrong with that. The only reason you would need to do anything different to what you have would be if you needed to main bond something extraneous in your garage.

 

[baldsparkies]

Don't know about Elecsa , but the NIC don't count work on you're own property...

That's not true.
NIC do asses on work at your property.
And using the 3rd core of an armour supply as a cpc may well be compliant, other factors pending.
Its been done many times.
This is why you should always check info, or advice received on forums.:icon12:

 

[R G]

That's not true.
NIC do asses on work at your property.
And using the 3rd core of an armour supply as a cpc may well be compliant, other factors pending.
Its been done many times.
This is why you should always check info, or advice received on forums.:icon12:

Well thats what they told me a few years ago mind you ...

 

[Guest125]

My understanding that exporting the PME is only an issue if you are doing it to a building that is a metal structure type. (Container/feeder pillar). Exporting PME to a brick built shed is fine.

 

[baldsparkies]

Well thats what they told me a few years ago mind you ...

One thing I have learnt over the years.
Where the NIC are concerned, NEVER believe ANYTHING they tell you.

The assessor won't give a ---- where the work is, if its compliant, its compliant, and so will you be.
After all they want you on board, there's money involved :icon12:

 

[Engineer54]

Here we go again!! Yet another Electrical Trainee that is prepared to drop a perfectly good PME earthing system in favour of a buckshee TT effort, that will undoubtedly turn out be rubbish. That doesn't understand that you are not exporting anything, you are merely extending an existing equipotential zone. If you actually have ''Any'' extraneous metalwork within this garage then you'll need to comply with PME main bonding requirements....

There are probably more threads here on this particular subject (exporting PME to outbuildings) than any other, so i suggest you take a little time (or rather a long time lol!!) to check those threads out!!

 

[PEG]

I am not going to knock the OP on his terminology,but if he is fresh from training/apprenticeship etc,i wonder who it is,that keeps the term "exporting" alive?

When terminology and nomenclature,are important,even critical,in a trade,why are some instructors happy to use such descriptions?

My pal exports horses,but i bet if i asked him to extend one,i'd get the curly finger...:icon12:

 

[darren1981]

Thank for info only going down the tt route as the existing swa is 2.5 so I haven't got a correctly sized earth by using tt I only need a cpc in the swa and my main earth bond to my new and tested earth rod

 

[telectrix]

if you only need a cpc and not 10mm bonding, then why on earth (pun intended) do't you use the PME?

 

[Engineer54]

Thank for info only going down the tt route as the existing swa is 2.5 so I haven't got a correctly sized earth by using tt I only need a cpc in the swa and my main earth bond to my new and tested earth rod

You state you have no water/gas service pipe work within the garage, so what extraneous metal parts are you talking about that requires main bonding??

 

[baldsparkies]

You need to check out other threads on the forum to save going over old ground.
This is also a useful read.

http://static2.voltimum.com/sites/w...hers/6/2005101314414308iee_outdoor_wiring.pdf

Unfortunately where pme systems are in use, main equipotential bonding to outbuildings (only where applicable) can turn into a sledge hammer to crack a walnut scenario.
And all in the name of catastrophic failure of the neutral.
Only seen it happen once, and the size of earthing was the last thing on there mind.
All those fried single phase appliances were the talking point.

 

[davesparks]

Thank for info only going down the tt route as the existing swa is 2.5 so I haven't got a correctly sized earth by using tt I only need a cpc in the swa and my main earth bond to my new and tested earth rod

What extraneous conductive parts are there in the new garage if you have no water or gas services in there?

 

[telectrix]

perhaps it's got metal window frames.:49:

 

[DPG]

Or a bonding cable running to each of the spanners hung on the wall? Daz

 

[darren1981]

The garage has structural steel work manly steel ridge doubt this ecp but would need to test this and a steel across door way. Unless a clad this in upvc ???

 

[telectrix]

Or a bonding cable running to each of the spanners hung on the wall? Daz

now you're getting silly.stop it.

 

[darren1981]

The garage has structural steel work manly steel ridge doubt this ecp but would need to test this and a steel across door way. Unless a clad this in upvc ???

Should I go mad and bond my steel tool boxes or just flot the whole garage on a timber raft

 

[davesparks]

The garage has structural steel work manly steel ridge doubt this ecp but would need to test this and a steel across door way. Unless a clad this in upvc ???

So just a steel ridge beam and a steel lintel then? Are either of them in contact with the ground?

Why not establish whether bonding is required of not before discarding a very reliable earth connection in favour of a potentially unreliable one

 

[baldsparkies]

perhaps it's got metal window frames.:49:

Plus a copy of the 15th !!
He's gonna need a lot of G/Y singles.
And if its got a petrol pump in there forget PME lol

 

[electroyd]

the garage as said is a brick building with no extraneous conductive parts to worry about.
nothing wrong with exporting the TNCS system to an outbuilding.
Different for a metal constructed outdoor car charger for example

 

[Leesparkykent]

What's all this talk about exporting earths? Lol

 

[electroyd]

What's all this talk about exporting earths? Lol

it sounds lovely