Radial vs Ring Circuit. What is better?

oliboni.n.lee

Would anyone advise me what is better for a 3 beds house, radial or ring circuit and why?

Thanks

Everton

2011

Radial. Off the top of my head:

1) For slightly less cabling twice the number of radial circuits are possible, offering more redundancy.

2) A radial circuit is safer: In the event of a single fault a ring circuit will continue to function, increasing the risk of an overland condition.

3) Less outlets permitted per circuit, it could get ridiculous with ring circuits with some electricians using only one or two ring socket circuits to cover an entire house.

4) Higher risk of wiring error with ring cabling form different circuits getting mixed up. This should be discovered during testing but isn't always as many electricians are weak on testing.

tweek84

2011 wrote: »

4) Higher risk of wiring error with ring cabling form different circuits getting mixed up. This should be discovered during testing but isn't always as many electricians are weak on testing.

Ring isn't used that often in Ireland and the above is a big concern.

For a kitchen it needs to have two socket circuits, for a 3 bed house it is hardly worth using a ring circuit as it would be of no benefit and in future if you decide to modify circuits it is slightly more difficult, i can't remember the regulation regarding spurring off ring circuits.

Risteard81

Ring final circuits are perfectly safe if correctly erected and verified. They also provide cpc redundancy. I vote ring final circuits (although in reality the correct answer is whichever suits the particular circumstances better).

2011

Risteard81 wrote: »

Ring final circuits are perfectly safe if correctly erected and verified.

Agreed.

They also provide cpc redundancy.

Nope.
In electrical engineering terms stating that this provides CPC redundancy is not correct.

If there was true CPC redundancy it would be possible to break the CPC ring and the minimum disconnection time could still be met (just like it was when the ring was intact), this is not the necessarily the case.

Bruthal

2011 wrote: »

Agreed.



Nope.
In electrical engineering terms stating that this provides CPC redundancy is not correct.

If there was true CPC redundancy it would be possible to break the CPC ring and the minimum disconnection time could still be met (just like it was when the ring was intact), this is not the necessarily the case.

I'd agree, no true redundancy alright.

2011

Bruthal wrote: »

I'd agree, no true redundancy alright.

Even though I "won" in the other thread ?? :P:P:D:)

Risteard81

How is it not the case? A ring final circuit serving socket outlets must be RCD protected therefore disconnection times are assured - a fault of 150mA or greater will disconnect within 40mS. A fault of negligible impedance between phase and Earth will be a great many times greater than this.

2011

Risteard81 wrote: »

How is it not the case? A ring final circuit serving society outlets must be RCD protected therefore disconnection times are assured - a fault of 150mA or greater will disconnect within 40mS. A fault of negligible impedance between phase and Earth will be a great many times greater than this.

Do you understand how earth fault loop impedance of a circuit is a function of disconnection time of that circuit?
Yes / No

Bruthal

Risteard81 wrote: »

How is it not the case? A ring final circuit serving society outlets must be RCD protected therefore disconnection times are assured - a fault of 150mA or greater will disconnect within 40mS. A fault of negligible impedance between phase and Earth will be a great many times greater than this.

Does the cpc not have to meet MCB based results now?

After all, redundancy would suggest a backup of equal ability to original. That's not the same as a lesser cpc which will still operate the rcd.

Risteard81

Obviously. Do you understand that a 30mA RCD will disconnect with as Earth Fault Loop Impedance up to 1667 Ohms?

2011

Risteard81 wrote: »

Obviously. Do you understand that a 30mA RCD will disconnect with as Earth Fault Loop Impedance up to 1667 Ohms?

You know that you should not rely entirely on the supplementary protection provided by an RCD? This disconnection time must be met by the over current device.

Risteard81

2011 wrote: »

Risteard81 wrote: »

Obviously. Do you understand that a 30mA RCD will disconnect with as Earth Fault Loop Impedance up to 1667 Ohms?

You know that you should not rely entirely on the supplementary protection provide by an RCD? This disconnection time must be met by the over current device.

I never suggested it should be relied upon. I pointed out that it was incorrect to suggest that the circuit suddenly wouldn't disconnect in the required time though.

Incidentally the IEE Regulations do permit the use of RCDs where the Earth Fault Loop Impedance is too high for the overcurrent protective device.

2011

Risteard81 wrote: »

I never suggested it should be relied upon. I pointed out that it was incorrect to suggest that the circuit suddenly wouldn't disconnect in the required time though.

First off all not all ring circuits are socket circuits so not all are required to have an RCD fitted.

Secondly when you make a statement about redundancy the implication is that there is true redundancy in a manner that is compliant with the regulations. Clearly this is not the case.

You seem to agree that the disconnection time must be met for the over current device (post 13).

I think that you also agree that a higher earth fault loop impedance will result in an increased disconnect time? You have yet to confirm. Assuming that you accept this fundamental principle then it naturally follows that the impedance of two CPCs in parallel is less that one and this could result in a minimum disconnection time being exceeded.

Risteard81

With a B32 MCB you would need an EFLI exceeding 230/5/32 = 1.44 Ohms to not have instantaneous disconnection (0.01 - 0.1 seconds) so your point still isn't terribly valid except in extreme circumstances.

What do you believe ring final circuits are used for other than socket circuits anyway? (And I am referring to ring final circuits and not ring mains before you claim that they are used in distribution.)

2011

Risteard81 wrote: »

With a B32 MCB you would need an EFLI exceeding 230/5/32 = 1.44 Ohms to not have instantaneous disconnection (0.01 - 0.1 seconds) so your point still isn't terribly valid except in extreme circumstances.

There are "extreme" circumstances out there.
A break in the CPC can cause the final circuit CPC impedance to double.

What do you believe ring final circuits are used for other than socket circuits anyway?

I have seen this done long outdoor lighting runs.

Grimwar

tweek84 wrote: »

Ring isn't used that often in Ireland and the above is a big concern.

For a kitchen it needs to have two socket circuits, for a 3 bed house it is hardly worth using a ring circuit as it would be of no benefit and in future if you decide to modify circuits it is slightly more difficult, i can't remember the regulation regarding spurring off ring circuits.

A 13 Amp fused outlet. same 13 Amp fuse as in a plug.

Any spur off a radial or ring circuit is regarded as a non-fixed device, the rules state the above fuse sizes.

To OP, why even consider RING, What are you going to plug in? Just do another RADIAL CIRCUIT, to cover your demand.

Bruthal

2011 wrote: »

Even though I "won" in the other thread ?? :P:P:D:)

Anyone who doesnt have some idea how the test button on an rcd works, may give up:pac:

2011

Bruthal wrote: »

Anyone who doesnt have some idea how the test button on an rcd works, may give up:pac:

How is it that RCDs cause so much confusion?
The discussion on this thread is a prime example!

Bruthal

2011 wrote: »

How is it that RCDs cause so much confusion?
The discussion on this thread is a prime example!

As in?

I dont think they cause as much confusion as you believe, they are not a lot more complex than a light switch.

Grimwar

A residual current device, has nothing to do with a ring or a radial circuit.

These circuits are protected in domestic Houses by a Miniature Circuit Breaker. (MCB) {not in industry as Fuses are needed here for motors starting currents} [also older houses may still have a Fuse board]

The MCB or Fuse is designed to protect the cable. In a radial circuit the
size is smaller than a Ring. But a problem that can happen on a
Ring circuits is.
If at any point in a Ring the cable is damaged or a connection in a socket outlet brakes, then you may have TWO Radial circuits protected by a device designed to protect a Ring circuit.

Bruthal

Grimwar wrote: »

A residual current device, has nothing to do with a ring or a radial circuit.

I thought only rings had them...

Joking of course. In a joker mood this week.

Johnnywaters

I believe they have a place in industry but not in a domestic installation.

Bruthal

Johnnywaters wrote: »

I believe they have a place in industry but not in a domestic installation.

Edit.. you meant rings. Thought you meant RCDs

Grimwar

Bruthal wrote: »

I thought only rings had them

I was implying the correct way to protect a cable.
ie: a 2.5 cable in a Radial vs a Ring circuit layout.

You never as a electrician [and as the rules state] protect a device.
You protect the cable your installing.
That is the Elections job.

The RCD has nothing to do with cable sizes or the correct MCB size.

Tuco88

The type A to a degree, and B variety RCD can detect DC pulse and direct fault currents. I want to see the the AA battery is racist.

+1 on the radial and Keep it country.

The Ring final has its pros and cons. A break or erroneous connection are the two possible flaws for me.

Not to say final rings dont have a use, and are perfectly safe as designed. Each to there own in the end.

All RCBOs are the way to go. A modern dwelling can have several socket circuits.Trying to find an intermittent fault over several circuit's is not practical at all.

FranklinMint

Tuco88 wrote: »

The type A to a degree, and B variety RCD can detect DC pulse and direct fault currents. I want to see the the AA battery is racist.

+1 on the radial and Keep it country.

The Ring final has its pros and cons. A break or erroneous connection are the two possible flaws for me.

Not to say final rings dont have a use, and are perfectly safe as designed. Each to there own in the end.

All RCBOs are the way to go. A modern dwelling can have several socket circuits.Trying to find an intermittent fault over several circuit's is not practical at all.

That reminds me of a certain organization who when called upon to investigate nuisance tripping would test the final circuits and RCDs or RCBOs for correct operation.

Anything outside of that like portable appliances wasn't their problem.