High integrity earthing

[Deleted member 26818]

Offices where there are lots of computers, School computer rooms, internet cafes etc.
You should also consider other items of equipment such as TVs, game consoles, stereos even washing machines and microwaves. Then there's alarm systems and these new controlable lighting systems to consider.
In fact just about any item of equipment that uses a PLC can have earth leakage.
Older desktop PCs can have as much as 3.5 mA, so an office or internet cafe with 3 or more PCs could easily top the 10mA limit.
I believe the NICEIC video even shows earth leakage from something connected to a fish tank?

 

[Guest 004]

Offices where there are lots of computers, School computer rooms, internet cafes etc.
You should also consider other items of equipment such as TVs, game consoles, stereos even washing machines and microwaves. Then there's alarm systems and these new controlable lighting systems to consider.
In fact just about any item of equipment that uses a PLC can have earth leakage.
Older desktop PCs can have as much as 3.5 mA, so an office or internet cafe with 3 or more PCs could easily top the 10mA limit.
I believe the NICEIC video even shows earth leakage from something connected to a fish tank?

so any hi integ circuit would not be protected by an RCD then

 

[telectrix]

well, it would if considered necessary for the safety of users, but you would be limited to the number of, say, pc's you could connect via the rcd. this would be a deserving case for rcbo's .

 

[Deleted member 26818]

RCD protection would still be required, it may mean however that the installation is divided up into more circuits.
I don't know what equipment a typical household would have.
My Sister's house has a 30 odd inch LCD TV in the front room, along with a desktop PC and a Wii. In the back room there's a 40 odd inch LCD TV with a surrond sound system and a tumble dryer, there may be a stereo as well.
In the kitchen is a small LCD TV, washing machine, a dishwasher, microwave, fridge freezer and quite a large cooker.
Upstairs there's another 40 odd inch LCD TV and a Playstation 3.
All of the items will have varying levels of earth leakage, if there were just one RFC downstairs, the combined earth leakage could well be above 10mA.
Both my Nephew and my Sister have laptops.

 

[Guest 004]

I am going to stick with what I read in the PDF article,

 

[Deleted member 26818]

Just out of interest, what is it that differs in the article to the information I have provided?

 

[IQ Electrical]

It's a big deal in schools and offices now but I'll say categorically that I've yet to see this mythical 3.5mA or anything approaching 3.5mA on the IT room equipment that we test.

The move to laptops in many schools and offices seems to have helped too, probably because the more modern switch-mode power supplies seem to have far less earth leakage.

I think when the op mentioned an 'insulated earth bar', he was confusing clean earthing with high integrity earthing.

 

[Guest 004]

Just out of interest, what is it that differs in the article to the information I have provided?

The fact that you can put the hi integ earths in the same terminal at the DB as long as they are labelled

 

[Deleted member 26818]

The fact that you can put the hi integ earths in the same terminal at the DB as long as they are labelled

I'd suggest you look again, at the diagram in the article.
I think you'll find that it shows the conductor ends for the high integrity earth circuits in separate terminals.
Tthe reason they are labelled, is so as they can be identified because they are not in the same terminals.
The only problem I have with the diagram, is that it does not show how the connections are made for a RFC when two CPCs are used.

 

[Guest 004]

I suggest you read the document again from start to finish, then look at circuit 2 which is a radial, but has the hi integ earth terminated on the same terminal as the cpc of the said radial