TheRick

I've got a couple (several dozen actually, but will start with just a couple) of questions about the British Standard.

First some background, I am a Licensed Master Electrician in the State of Maine, but am now working in Iraq. I am working as an inspector, and am now being asked to inspect facilities based on the BS. I have a PDF copy of the British Standards 16th edition and have been brushing up on it.

My big question is on earthing, I will be inspecting installations with the TN -S and the TN-C-S systems. In a Life Support Area (LSA) here on base there are anywhere from 100 to 400 Containerized Housing Units (CHUs) so an LSA basically resembles a trailer park in the states. In a 4 wire TN-C-S system with a combined Protecive and Neutral Conductor the diagram in the code book shows an "additonal source earth" but is pretty vague as to it's location. We have a situation where one set of feeders will feed into a CHU, and then daisy-chain along to feed several other CHUs.

In this application where should this additional source earth connection be made, and how many are required.

It is also my understandig that in a TN-S system with 5-wire feeders there is NO requirement for earthing other than at the source...is this a correct assumption?

Thank you for any and all help...more questions to follow!

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Rick -

"fool-proof systems do not take into account the ingenuity of fools"

Trimix-leccy

Mmmmm, this should be a good one

Firstly 16th edition is no longer used, it is now 17th edition as of July 1st this year. BUT it depends on what you are asked to test/inspect to really.

TN-S and TN-C-S are not usually mixed

on a TN-C-S sytem you have to be careful about importing earths. Prob not an issue if you have plastic water / gas pipes going to each unit BUT if they are metal or you have local earths via gas /water pipes etc you will most likely need individual earth rods along with local earthing of each unit if it is a TN-C-S system

Since you are versed in the US code be warned.......Neutral and earth are never ever combined anywhere within an installation never never never, not in a board, nowhere never never. Also, one circuit one neutral.

Sounds like an interesting job

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TRIMIX...Deep down you know you want it! Trimix-leccy; pulling the envelope---not pushing it

TheRick

Figures...but the 16th is what I have been given to use.

There is nothing "usual" about this job.

No water or gas to any of the housing units, there are seperate toilet and shower facilities(I have more questions about them later). My thought looking at the diagram in the code book was to require one additional source earth connection per feeder circuit, which would be feeding anywhere from 2-6 housing units. These are simple one room approx 8 foot by 20 foot units, basically just sleeping quarters for soldiers.

I am figuring that out...also no earthing connections if fed with 5 wire from the source correct?

You can say that again

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Rick -

"fool-proof systems do not take into account the ingenuity of fools"

Trimix-leccy

I'll dig out my old 16th edition tomorrow and have a look.

TNS

ALL 3 phases along with Neutral and Earth are seperae throughout...so for the earth it would be daisy-chained from the first one. BUT the size may have to be increased above the normally expected size to accomodate the extra length to ensure that the eath loop Zs is low enough to trip the protection on fault

See if your 'employer' will get you a copy of

Testing Electrical Installations. A Practical guide for Electricians, by Anthony Hinsley. ISBN 0-952-5324-1-7. It is about 7 years old but should show you the practical hands on side of testing.

Keep posting and I'll [we'll] try to keep answering

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TRIMIX...Deep down you know you want it! Trimix-leccy; pulling the envelope---not pushing it

TheRick

I will...and I appreciate the Help

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Rick -

"fool-proof systems do not take into account the ingenuity of fools"

TheRick

Been reading Section 601...if I understand it properly there are no socket outlets allowed in Zone 3 of a shower room except for SELV circuits, or shaver units. Is this correct?

I was able to download a copy of the book you recommended...looks like it will be a huge help.

THANKS

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Rick -

"fool-proof systems do not take into account the ingenuity of fools"

Trimix-leccy

Correct. [and remember that the shaver unit HAS to be one with an isolation transformer built in]

Now if you were testing to 17th edition NO zone 3! BUT everything in a 'bathroom ' has to be protected by an RCD [GFCI ??] AND in most cases there is no need for bonding AND.....it goes on and on and on and on and


How are these bathrooms being bonded?....should be a good one

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TRIMIX...Deep down you know you want it! Trimix-leccy; pulling the envelope---not pushing it

John

These may be a little help ...maybe.
Attachment 875
Attachment 876

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Doubt All Before Believing Anything.......

TheRick

The shower rooms and latrines all have feeders, and panels installed in them with 30mA RCD mains in the panels...or at least they will when I am done. My concern is if I have all the receptacles removed I will be angering several thousand soldiers I know that pi$$ing them all off is better than killing even one, but if everything in the unit is RCD protected and wired properly I frankly have bigger fish to fry.

Most of the piping is actually PVC, so no need of a bond there, the ones with copper piping are actually well bonded to the piping. A problem we have seen with the shower/latrine units, and the living units, is that the metal framing of the structure has not been bonded. They have been working to correct that, but it is going slowly.

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Rick -

"fool-proof systems do not take into account the ingenuity of fools"

sparkie

see other thread for my reply on mobile units, secondly main equipotential bonding should be fitted to building frame and any water/gas/service entering the building.
If you can get them I would suggest main switch and rcbo's if money no issue and nuisance tripping is.

TheRick

The bonding to the building frame is being corrected...slowly but surely.

You mention RCBOs...how do they reduce nuisance tripping? If I understand correctly, they are basically and RCD with overcurrent protection. I am trying to learn all of the British terminology, but it still gets confusing at times.

Thanks for your help

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Rick -

"fool-proof systems do not take into account the ingenuity of fools"

frenchelectrican

Sorry to step in here due I am in France now and the regulations related to the shower room unforetally it is correct for both UK and France verison and now the do allowed the RCD { GFCI } but at diffrent trip setting beside the main CU { Customer unit }

If feed from Generator power you will have to follow the same regulatons as normal uility system is.

AFAIK the UK RCD and RCBO they will not only open the Hot conductor and they will open the netrual conductor as well { UK guys correct me if I am wrong on this one }

And the other tibbit the RCD's are set at somewhere in 30 to 500 MA range depending on the set up and how big the CU is.,

However the RCBO have much lower setting IIRC about 25 to 50 MA { this part I need to dig up to make sure I get correct info }

Merci,Marc

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Bleu est beau.

steelsparks

Hi Guys

Been surfing various electrical topics on the web and came across your thread.
As i'm currently working in Iraq on bases i often work on the accomodation huts.
There really are some very bizarre (and downright dangerous) practises going on mainly due to different nationals working on them.


RCBOs are principally overcurrent protection devices known as MCBs(miniture circuit breakers) with the addition of RCD protection usually 30ma.
They are used on individual circuits and are 2 pole isolating (or 3/4 pole depending on application) ,the convenience of these is to operate independantly of each other so as to keep power to adjacent circuits.

They wouldn't stop nuisence tripping just curtail its effect on existing power distribution.

Hope this helps. . .

sparkie

nuisance tripping would be a faulty kettle taking out the whole board, eg lights as well