Creating a clean earth

[Rockingit]

TNC-S supply, what's the best way to create a separate clean earth for some dedicated outlets? Ignore the MET and bring a dedicated earth back to a separate rod?

 

[La Poste]

Why do you want a clean earth if you don't mind me asking?

 

[Rockingit]

Audio equipment in large buildings, basically.

 

[trev]

It's the only way I can think of Chris. Interesting question though, are you back in your old roadie life again?

 

[malcolmsanford]

On our IT systems over here the american part of the design team, still ask for Clean grounding. We do this simply as we wrote

The best way to reduce noise to a minimum is to use a copper grid ground plane. This technique is often used for ‘computer rooms’ when data processing was centralised and is still frequently the only viable solution. It works because there is an infinite number of paths through the grid with different apparent electrical lengths – while some of these paths may be multiples of a quarter wavelength, there will undoubtedly be many other parallel paths which are not. The result is a low impedance connection over a wide frequency range. Such a grid should cover the whole of the area of the installed equipment – these days usually the whole building – and it should not be forgotten that this applies to the vertical direction as well as the horizontal. There is little point in having horizontal meshes on every floor connected to a single vertical downlead. Grids are normally constructed using flat strip to keep skin effect to a minimum. Where structural elements are used as a grid, such as the supports for a raised floor that have been selected for their mechanical rather than electrical properties, it is important to ensure that the elements are electrically bonded together – using short copper braids – at each intersection.

So to get a cleaner earth, produce loads of different paths, but on a small scale a couple of rods

 

[Rockingit]

Not so much back in it, as having a busmans holiday! It's a question of curiosity more than need; I'm in the brand new built Qatar National Convention Centre for a couple of weeks and it's all very very expensive and state of the art and I was looking at something in the theatre section which has clean earths and realised that even though I've USED them for years, I've never had to think about how they got there!! Maybe E54 might be able to enlighten us!

On another note, this place may be state of the art, but the locals who have been handed the complex now it's been finished don't have the first clue. So whichever electrical engineers stayed up late into the night to design this place shouldn't have bothered as the house 'electricians' don't even know where half the panels are, can't understand the plans left on site and don't even know where light switches are or the difference between a socket switch and an RCD ffs. I had to stop one of them from killing himself the other day when he wanted to stick a screwdriver down a 32/3 ceeform to see if it was live, whilst 60' up on a picker with no harness.

 

[malcolmsanford]

your lucky he was using a screwdriver .................have you marveled yet at the safety footwear ................commonly known as the flip-flop

 

[Rockingit]

Flip-flop? Luxury!! (see ladder thread!).

Seen much worse elsewhere, to be fair. India has been my biggest eye opener so far, that place really did make me shudder. Mexico is probably second. Just been chatting with some guys here about Saudi, ironically, and they were telling me it's here ^10! I've spent a fair amount of time in Dubai and Abu Dhabi and by comparison those guys are pro's!!

 

[malcolmsanford]

I went on site the other day ..........to be met by an engineer of dubious mode, who had the hard hat, hiv viz jacket and the flip flops ...................so that was a good start ...............

Then going around saw the lad knocking up his ladder, mostly made of 2 lengths of 2x2 with various lengths of 2X1s nailed into at various stages to imitate rungs .....................

Just shake your head now, and much to my disgust actually ignore it, as I have tried and tried to change them, even giving tool box talks, which was a real eye opener .................

Not sure what the average life expectancy is of a sub continent worker ..............

 

[trev]

Oh the joys of Saudi. It still scares me to think of it now

 

[Engineer54]

From what i can gather of what Malcolm was describing, is a IT grounding system which is split similarly to a medical room set up, where you have what is known as a PA earth and PE earth system, both being isolated from each other. Although this arrangement is a form of clean earth, it's probably not viable for your small requirements, as it relies on an IT transformer fed via a mains/generator/UPS supply.

What your looking for, is a straight forward clean earth, which is completely separate from the Building/MET earth, and the easiest way to achieve that, is by the use of earth electrodes that are not under/in the influence of any other earthing arrangement. Your probably going to need RCD protection on top, as it's doubtful your going to get decent enough values to trip a breaker. Not unless the soil/sand is full of sulfates and chlorides etc...lol!!

So your initial thoughts were correct...

 

[Rockingit]

So your initial thoughts were correct...

goes into smug mode.......