High integrity earthing

[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

 

[Deleted member 26818]

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

Looking at the diagram, terminal 1 has a conductor labled circuit 1 and one labled circuit 2. Terminal 2 also has a conductor labled circuit 1 and another labeled circuit 2.
I don't see how you can confuse maters and believe that both conductors from the radial (circuit 2) are in the same terminal?

 

[Guest 004]

A radial circuit will only have one earth in normal circumstances, as a diagram it is poor, but clearly shows the hi integ earth with the cpc of the circuit. On the previous page it is stated how to overcome the earth connections on a DB which does not have additional earth bars, and at full capacity

 

[Deleted member 26818]

Yes the diagram is not very good, but are you seriously stating that you cannot see that the conductors with arrows pointing at them marked 'circuit No 2' are in separate terminals?

 

[Guest 004]

Yes the diagram is not very good, but are you seriously stating that you cannot see that the conductors with arrows pointing at them marked 'circuit No 2' are in separate terminals?

Good heavens old chap, indeed I stand corrected. Thanks for pointing that out.

I think the diagram should show 3 earths in the first terminal.

Kind of brings the point home though.

Thanks again

 

[Deleted member 26818]

Yes if using two CPCs for the RFC, I would also expect there to be three earths.

 

[Guest 004]

Couple of questions to add

1. Are there any new values for Zs for this type of install?
2. If the combined earth does not equal 10mm is it still considered an HI circuit? even though the earths have been terminated into there own terminals?

Just having a little debate with the resident tester that's all, would like some concrete ammo

 

[Deleted member 26818]

No the Zs values for the circuit remain the same, however each of the CPCs must be sufficient to satisfy the mazimum Zs values for the CPD on their own.
The 10mm² value refers to non-copper conductors such as the armour of SWA or metal conduit. It also refers to the total CSA of all conductors when a multi-core cable is used for instance 1.5mm² 3 core & earth would not be allowed, as the total CSA of all the conductors is only 5.5mm². Even 2.5mm² 3 core & earth would not be acceptable, as the combined CSA would only be 9mm², although 2.5mm² T&E with an additional 2.5mm² (if mechanically protected) would be.

 

[Guest 004]

The circuits in question are twin and earth 2.5mm RFC's and installed on basket, with no other mechanical path, so IMO this fails miserably

 

[Guest 004]

The circuits in question are twin and earth 2.5mm RFC's and installed on basket, with no other mechanical path, so IMO this fails miserably

I stated this to the resident tester, and his response was "no no no, there is another reg, " , but indeed he could not quote it.

 

[Guest 004]

I stated this to the resident tester, and his response was "no no no, there is another reg, " , but indeed he could not quote it.

I read again, the regs has an 'or' included, so the circuit can have 2 separate earths of 1.5mm 'or' a combined value of 10mm. A bit ambiguous it would seem.