Dangers of ring final circuit

[Baker1988]

Hi i have been set some home work from college to find out why ring final circuits are dangerous. I know the obvious that if one leg on the ring breaks it will not be a full ring and the 32 amp mcb will be too big for the cable as it will only be able to carry about 20 amps with out it been a ring which would over load the cable. But i can not find any thing other then what i already new can any one help me with this

 

[johnboy6083]

what would cause a break in the ring, other than manual intervention? Maybe rodent damage, or drilling though a cable, but that would cause short circuit, which would operate the potective device.

 

[needasparks]

I totally agree with you E54,
Ive lost count the amount of times i have been on the phone to my son's college about the poor teaching and wrong information they are pumping out, the best one was that asbestos does not exist in any type of switchgear and i should know as ive been on the tools for 15 yrs, believe it or not this was from a H&S lesson.

 

[Guest123]

what would cause a break in the ring, other than manual intervention? Maybe rodent damage, or drilling though a cable, but that would cause short circuit, which would operate the potective device.

Number 3 on your list John.

Although a million to one shot, conductors becoming loose at their terminals over time 'could' cause a situation as described which may go unnoticed for a good length of time.

Highly improbable for both L&N to work loose but........

 

[Sparky Ninja]

I think you guys are taking this a little too serious.

I've asked similar a question to my students before, not necessarily that rings are dangerous, but more about there opinion to the potential dangers a ring final can create when under the control of "ordinary persons".

and the answer is YES. Ring final circuits are more dangerous.

 

[johnboy6083]

Number 3 on your list John.

Although a million to one shot, conductors becoming loose at their terminals over time 'could' cause a situation as described which may go unnoticed for a good length of time.

Highly improbable for both L&N to work loose but........

fair point lenny. is this more dangerous than any terminal working loose though, lets face it either a loose live, or neutral will probably cause a fire or burning on any circuit, long before it works completely loose.

 

[brman]

As I said in post #7, that is the biggest risk of an RFC, as the householder would not be aware of it so the cable may if heavily loaded, be operating outside of it's capacity.

So you did. Which is why am puzzled that the lecturer is getting abused for asking a question that has a valid answer.

 

[Engineer54]

So you did. Which is why am puzzled that the lecturer is getting abused for asking a question that has a valid answer.

I take it, you don't like RFC either??

 

[telectrix]

if i read the op correctly, the question was "why is a ring final circuit dangerous?", not "how may a RFC become dangerous"?. apart from a leg going O/C, there is the potential for the 2 legs to be fed from different OCDs. that would be dangerous. but, as has been said, it's a potential danger, not an inherent danger.

 

[MarkieSparkie]

An unbiased view of advantages and disadvantages of Ring versus Radial.

Note:- In the following list of advantages and disadvantages of Ring and Radial final circuits. Some points are followed by a question mark because supporters of each type like to argue their best case, but it like most things in electrical engineering it’s not really "black and white" it depends on what is compared with what.

The Ring Final Circuit Camp argue the 32A, 2.5 T+E, Ring Final Circuit versus the 32A, 4 T+E, Radial Final Circuit.
Whereas the Radial Final Circuit Camp argue the 20A, 2.5 T+E Radial Final Circuit versus the 32A, 2.5 T+E, Ring Final Circuit.

Advantages of the Ring Final Circuit:
1) It reduces the amount of copper used in an installation?
2) It reduces the number of circuit protective devices
3) It helps to reduce voltage drop
4) It has proved its value over the last 60 years
5) It promotes sustainability in design
6) It is good for the Environment?

The disadvantages of Ring circuits are numerous:
1) Compliance with Regulation 433.1.103
2) Not understood – lack of training of electricians from other countries
3) Susceptible to fault conditions
4) Testing and fault finding is very time consuming and costly
5) Fault conditions are not apparent when in use
6) Use more cable and take longer to install compared to 20A Radials – waste of resources?
7) Generally not cost effective compared to 20A Radials

Advantages of Radial circuits:
1) Greater flexibility
2) Less cable would be needed
3) Less time to install
4) Lower installation cost?
5) Less drain on the world’s resources of copper?
6) The problems created by Regulation 433.1.103 – distributing load evenly in a ring circuit (that nobody takes any notice of) would disappear thus reducing the exposure of the contractor to a breach of regulation claim.
7) Considerably less time required for inspection and testing.
8) Less likelihood of installation faults
9) Any breaks or loose connections will be readily identified when testing.

Disadvantage of Radial circuits
1) More circuits required
2) Larger distribution boards
3) More circuit breakers required

 

[Geordie Spark]

I seem to remember when I was doing the 16th Edition an college, the lecturer said he preferred Radial circuits over Ring Finals because he felt that there was a greater potential for danger with RFCs.

 

[Engineer54]

If you look and study this list of advantages and disadvantages, there are some blatant contradictions.... In fact i'd go as far as saying there is not much evidence here to say this list is ''unbiased'' at all!! Into the bin with it!! lol!!

 

[brman]

I take it, you don't like RFC either??

not at all. Quite the opposite. I am just puzzled that the lecturer got a lynching for getting his students to think about why they might not be perfect.

 

[Engineer54]

not at all. Quite the opposite. I am just puzzled that the lecturer got a lynching for getting his students to think about why they might not be perfect.

Because he is WRONG to suggest RFCs are dangerous, they are not, and never have been. They can only become dangerous by interference, the same way any other circuit can...

 

[GLENNSPARK]

the question should of been to find the advantages and disadvantages of a ring final circuit. The question your tutor has set is very leading, and hes tryinmg to force his opinion on you.

IMO education should be about giving you the hard facts, and knowledege for you to make your own decsions.

yes....he`s clearly of the "anti ring final" camp.....rather than take his head out of the sand and realise that both ring and radial finals have their advantages and disadvantages ant the fact that you should assess the situation first....and then decide on the best course of action...such as ring or radial...diversity applied....MCB and type and CSA of cable to use etc.....what this lecturer is doing aint on....he`s trying to sow the seeds of doubt here in regards to what is a safe and recognised wireing system......

 

[GLENNSPARK]

An unbiased view of advantages and disadvantages of Ring versus Radial.

Note:- In the following list of advantages and disadvantages of Ring and Radial final circuits. Some points are followed by a question mark because supporters of each type like to argue their best case, but it like most things in electrical engineering it’s not really "black and white" it depends on what is compared with what.

The Ring Final Circuit Camp argue the 32A, 2.5 T+E, Ring Final Circuit versus the 32A, 4 T+E, Radial Final Circuit.
Whereas the Radial Final Circuit Camp argue the 20A, 2.5 T+E Radial Final Circuit versus the 32A, 2.5 T+E, Ring Final Circuit.

Advantages of the Ring Final Circuit:
1) It reduces the amount of copper used in an installation?
2) It reduces the number of circuit protective devices
3) It helps to reduce voltage drop
4) It has proved its value over the last 60 years
5) It promotes sustainability in design
6) It is good for the Environment?

The disadvantages of Ring circuits are numerous:
1) Compliance with Regulation 433.1.103
2) Not understood – lack of training of electricians from other countries
3) Susceptible to fault conditions
4) Testing and fault finding is very time consuming and costly
5) Fault conditions are not apparent when in use
6) Use more cable and take longer to install compared to 20A Radials – waste of resources?
7) Generally not cost effective compared to 20A Radials

Advantages of Radial circuits:
1) Greater flexibility
2) Less cable would be needed
3) Less time to install
4) Lower installation cost?
5) Less drain on the world’s resources of copper?
6) The problems created by Regulation 433.1.103 – distributing load evenly in a ring circuit (that nobody takes any notice of) would disappear thus reducing the exposure of the contractor to a breach of regulation claim.
7) Considerably less time required for inspection and testing.
8) Less likelihood of installation faults
9) Any breaks or loose connections will be readily identified when testing.

Disadvantage of Radial circuits
1) More circuits required
2) Larger distribution boards
3) More circuit breakers required

what do you mean at 9 on the radial list here Markie?.....so you dont do an r1...r2...rn...on a ring final then?...