High integrity earthing

[securespark]

Thanks for clearing that up, numerical!

 

[ban-all-sheds]

Now 602 - take a close look at 607-02-04 (iii) paragraph 2 - ring circuit (4 * 2.5) + (2 * 1.5) = ?

Here's a RFC:

How many cpcs does it have?

 

[333rocky333]

Any reason why the earths are terminated like that.

issue 26 wiring matters , spring 08
Adressed this subject , and shows, one ring cpc conductor, two connections on TWO seperate terminals at the CU, for an RFC.
Looking again at it, it is as you say.

I misread it as Four terminated cable ends, for the RFC, but what they have done is used term 1 for circuit 1 ring + circuit 2 radial (Second earth) , and term 2 for circuit 2 radial + circuit 1 ring.

 

[ban-all-sheds]

1) Dunno what the 17th requires, but mdbalson's kitchen is being done to the 16th.

2) The implication of the explanation in that Wiring Matters article is that confusion about the topology of a circle is not confined to members of this forum. A ring final circuit has one phase conductor, one neutral conductor and one cpc....

 

[NotHimAgain]

1) Dunno what the 17th requires, but mdbalson's kitchen is being done to the 16th.

2) The implication of the explanation in that Wiring Matters article is that confusion about the topology of a circle is not confined to members of this forum. A ring final circuit has one phase conductor, one neutral conductor and one cpc....

Dear me don't you ever give up

A ring final circuit is not a circle it is two routes to a supply source.

 

[ban-all-sheds]

A ring final circuit is not a circle

Topologically it is.

When you next test for continuity of ring final conductors, try to imagine in your mind what continuity readings you'd get if the two conductor ends in your meter crocs were the ends of two separate conductors, not one....

 

[NotHimAgain]

Topologically it is.

I afraid not - a circle fails to define the essential elements of a ring final circuit.

A circle has no node to source energy.
A circle has no node to sink energy.

The most basic domestic ring final circuit must have these elements to function. Once they are in place you have two routes between them.

A ring can be drawn in the shape of any single closed loop there is nothing special about a circle.

Now you can twist and turn all you like you will not be able to change these requirements.

If I have two routes - each delivering energy from the source to the sink - I have the number of conductors I indicated.

 

[SeanT]

to·pol·o·gy Audio Help (tə-pŏl'ə-j&#275 Pronunciation Key
n. pl. to·pol·o·gies


Mathematics: The study of the properties of geometric figures or solids that are not changed by homeomorphisms, such as stretching or bending. Donuts and picture frames are topologically equivalent, for example.

 

[ban-all-sheds]

If I have two routes - each delivering energy from the source to the sink - I have the number of conductors I indicated.

Please answer these questions:

You go to a CU, and you find a B32 with 2 x 2.5mm² conductors coming from it.

You remove them from the breaker, and apply your continuity tester to them.

1) What sort of values would you get if the two ends you connected your tester to were:

a) The ends of a single conductor?

b) The ends of two separate conductors?

2) What sort of values do you typically see when the breaker is supplying:

a) A ring?

b) Two radials?

3) From your answers to (1) and (2), how many phase conductors do the following circuits have:

a) A ring?

b) Two radials?

If I have two routes - each delivering energy from the source to the sink - I have the number of conductors I indicated.

Please draw us a ring final circuit with a source and 10 socket outlets. To make life simpler you may show just the phase, neutral or cpc elements.

Please state how many phase/neutral/cp conductors the circuit has, and add numbered arrows indicating which ones are which.

 

[NotHimAgain]

The values I get are not relevant because I can engineer them to be what ever I like.

However, I am at the CCU and I have two 2.5mm² conductor ends in the mcb terminal (or perhaps terminus) - so that is 2 * 2.5 = 5.

Next I go to the neutral connection bar and I remove the 2, 2.5mm² conductors related to my circuit. 2 * 2.5 = 5

Then I go to the earth connection bar and - you guessed it - I remove the 2, 1.5mm² related to my circuit. 2 * 1.5 = 3

Now I wonder what (2 * 2.5) + (2 * 2.5) + (2 * 1.5) equals - do you know?

 

[RF Lighting]

BAS, you seem to be missing the point here.

As I'm sure we are all aware, the purpose of high integrity earthing is to ensure that circuits designed to supply equipment with high leakage currents do not lose their connection to earth, as this could lead to all metalwork connected to the CPC rising to a dangerous potential.

A ring circuit is ok to use for this purpose providing both protective conductors are terminated independantly of each other throughout the entire circuit.

This is so if a screw is left loose, or works itself loose, there is still an earth connection to all the appliances on that circuit.

If both ends of the ring were terminated under the same screw, then one screw coming loose could lead to some or all of the appliances loosing their connection to earth.

According to BS7671, a radial circuit is permitted with a single protective conductor if that protective conductor is connected as a ring.

 

[Spark123]

The values I get are not relevant because I can engineer them to be what ever I like.

However, I am at the CCU and I have two 2.5mm² conductor ends in the mcb terminal (or perhaps terminus) - so that is 2 * 2.5 = 5.

Next I go to the neutral connection bar and I remove the 2, 2.5mm² conductors related to my circuit. 2 * 2.5 = 5

Then I go to the earth connection bar and - you guessed it - I remove the 2, 1.5mm² related to my circuit. 2 * 1.5 = 3

Now I wonder what (2 * 2.5) + (2 * 2.5) + (2 * 1.5) equals - do you know?

Does that not mean where both individual CPCs are in the same multicore cable?

 

[ban-all-sheds]

The values I get are not relevant because I can engineer them to be what ever I like.

The sort of values, or orders of magnitude of the values you get are extremely relevant.

However, I am at the CCU and I have two 2.5mm² conductor ends in the mcb terminal (or perhaps terminus) - so that is 2 * 2.5 = 5.

Let us assume that the conductor ends you have removed are those of a ring. When you connect your continuity tester to them to measure the conductor resistance, what order of magnitude would you expect the reading to be?

Let us assume that the conductor ends you have removed are those of two radials. When you connect your continuity tester to them to measure the conductor resistance, what order of magnitude would you expect the reading to be?

 

[scousespark]

The values I get are not relevant because I can engineer them to be what ever I like.

However, I am at the CCU and I have two 2.5mm² conductor ends in the mcb terminal (or perhaps terminus) - so that is 2 * 2.5 = 5.

Next I go to the neutral connection bar and I remove the 2, 2.5mm² conductors related to my circuit. 2 * 2.5 = 5

Then I go to the earth connection bar and - you guessed it - I remove the 2, 1.5mm² related to my circuit. 2 * 1.5 = 3

Now I wonder what (2 * 2.5) + (2 * 2.5) + (2 * 1.5) equals - do you know?

What does this mean?

 

[Spark123]

In response to 607-02-04 part (iii) I think