Ring or Radial

[bernardgreen]

how do you make note of that for the next electrician (which may not necessarily be you) so that he/she is aware of this circuit arrangement.

Full design notes given to the owner, including routing of cables and any complex circuits such as two way switching detailed.

From your last post, does this mean that the last time you wired a domestic property was in 1980?

Built the house in 1980. it was not the last install.

Again, with the greatest of respect, there have been a number of changes to the regs since then, times have changed

But basic electrical theory and practise has not changed. electrons remain following the same rules they always have done

But standards may have been dumbed down so that installers can work within a set of tables and guidelines without having to have any knowledge of how and why electrons behave the way they do.

 

[mikhailfaradayski]

again, with the greatest of respect, that answer is a bit wooly.

I was specifically interested to hear of how exactly you wrote/noted the nonstandard RFC on you EIC.

How did you set about evaluating the data that you specified as Zs for that circuit? was it a 'plug in, 3 lights, lets go' test or did you test your RFC as you would any other RFC?

I'm not sure that this has anything to do with dumbing down. I also think that discussing the movement of electrons has no relevance to the accurate recording of a value of Zs for the purpose of assessing disconnection times.

After all, it really is not rocket science, but it could be important to safety of others. (two way switching = complex???? OMG, really? )

But if you don't want to provide a straight answer, thats your choice. Happy new year anyway

 

[bernardgreen]

Straight answer.

My test methods are primarily intended for fault finding on installations that I did not install. First step is often working out how the installation cables run.

Using an isolated constant current source a 1 amp DC current is sent around the ring and the voltage across the ends of the ring is measured. This provides, with calculation, the DC resistance of the conductor being tested. This is performed on CPC, Line and Neutral conductors.

If the circuit is not a ring then a dual wander lead is used to connect to what is presumed to be the far end of the circuit. Dual in that one conductor of the wander lead carries the 1 amp currrent, this will have a voltage drop due to the current flowing in it. and the other conductor provides the reference for the measurement of the voltage. As the current in the reference lead is extremely small the voltage drop along it is insigificant ( less than 0.1 % ) compared to the voltage being measured.

By using the wander lead to measure and record voltages at each socket relative to the start of the circuit when the 1 amp test curent is flowing the order of sockets along the circuit can be determined.

The voltage measured is the voltage drop along the conductor with the 1 amp current flowing.

If two sockets provide the same voltage then one of them is a spur from the circuit with the 1 amp flowing through it taken from the socket with the same voltage.

This also indicates that the assumed end point of a radial is not the actual end point.

If the insulation tests show a low resistance short to CPC from neutral ( or live ) then a lower current is injected into the neutral ( or live ) and taken from the CPC . Measuring voltages between CPC and neutral ( or live ) will enable the location of the short to be found. Some care is needed in this process as injecting a high current may "burn out" the metal forming the fault leaving it temporarily cleared but still there.

So far I have not removed any socket faceplates so the fault has not been mechanically disturbed. An action which may "remove" the fault.

 

[dingbat]

Also, if it were assumed to be a radial with a spur at the cu and the inspecting spark used a live Zs test at each socket outlet, do you think he may be a little concerned/confused to find that the Zs at each socket was substantially the same, as opposed to varying along its length as you would expect to find on a standard radial?

But this would not happen as the Zs of each socket on a ring is NOT substantially the same, far from it. The only reason for that assumption would be an incomplete understanding of how the RFC test procedure works. (R1 + R2) values come out more or less the same because the test reconfigures the ring structure, but on reinstatement, the sockets nearest the origin will have the lowest Zs and be substantially lower than those approaching the midpoint.

 

[dingbat]

Straight answer...

Using an isolated constant current... 1 amp DC... voltage measured. ... DC resistance of the... CPC, Line and Neutral conductors... a dual wander lead ... presumed to be the far end of the circuit... one conductor ... carries the 1 amp currrent, this will have a voltage drop due to the current flowing in it. and the other conductor provides the ref...

blah...

blah...

blah...

Now see what you did Mikhael?


I hope you're happy with yourself!

 

[mikhailfaradayski]

Also, if it were assumed to be a radial with a spur at the cu and the inspecting spark used a live Zs test at each socket outlet, do you think he may be a little concerned/confused to find that the Zs at each socket was substantially the same, as opposed to varying along its length as you would expect to find on a standard radial?

But this would not happen as the Zs of each socket on a ring is NOT substantially the same, far from it. The only reason for that assumption would be an incomplete understanding of how the RFC test procedure works. (R1 + R2) values come out more or less the same because the test reconfigures the ring structure, but on reinstatement, the sockets nearest the origin will have the lowest Zs and be substantially lower than those approaching the midpoint.

ah, yes, my bad

thats sort of what i meant, but completely screwed it up. A combination of two different thoughts that transpired to be a nonsense.

I have no hangover today and it appears to have affected my thought process.

 

[B67BU]

The cartoon was written for a reason.

 

[ban-all-sheds]

For the three full domestic installs that I have carried out the owners and the the technical people in the insurance companies concerned were happy to accept the documents of design and test results I provided.

But not including, of course, EICs because you don't actually own a copy of the Wiring Regulations.

With a radial if there is a single fault on the CPC then down stream sockets have no effective CPC. On a ring they will have a CPC

Rather than radical departures from the regulations maybe the solution you should adopt is radials with a ring cpc.

Straight answer.
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Are you a friend of Nitros?