How are ring mains wired in the UK? It is my understanding that the hot goes to each receptacle and then returns to the breaker. Would this be allowed in the states? What is the advantage? They say that it is because the electricity can come from 2 directions. Maybe some of our expat or overseas members might give me some illuminations
Ring Mains or Ring Circuits
- Thread starter britt
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ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Ring Mains or Ring Circuits
Yes, if done in compliance with 310.4 for parallel conductors. Otherwise, no.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Ring Mains or Ring Circuits
Karl: Come help me here!
I agree with Dereck in that it is a very intriguing circuit, but in my opinion, it is a parallel circuit.
Karl: Come help me here!
I agree with Dereck in that it is a very intriguing circuit, but in my opinion, it is a parallel circuit.
Re: Ring Mains or Ring Circuits
If they are considered parallel conductors, I think they would violate 310.4 which seems to basically say parallel conductors must be the same length and have the same physical characterisics (ie. same size wire following approx. the same route).
Also I think this installation would violate 300.20 since the current on the hot wire would follow either of 2 paths and the neutral would have only one path. (Or are the neutral's ran in a ring also? If so one can't be sure that the current would split the same for both the supply and return current.)
Steve
If they are considered parallel conductors, I think they would violate 310.4 which seems to basically say parallel conductors must be the same length and have the same physical characterisics (ie. same size wire following approx. the same route).
Also I think this installation would violate 300.20 since the current on the hot wire would follow either of 2 paths and the neutral would have only one path. (Or are the neutral's ran in a ring also? If so one can't be sure that the current would split the same for both the supply and return current.)
Steve
- Location
- Illinois
- Occupation
- retired electrician
Re: Ring Mains or Ring Circuits
In a parallel circuit each wire must terminate at the same physical point at both ends. This is not the case with a ring circuit and multiple outlets.
Don
In a parallel circuit each wire must terminate at the same physical point at both ends. This is not the case with a ring circuit and multiple outlets.
Don
Ed MacLaren
Senior Member
Re: Ring Mains or Ring Circuits
britt,
It would be similar to the sketch below, except that I've only shown a few outlets.
There is a medium voltage ring feeder supplying the padmount transformers for the various buildings at our local university. Each transformer is supplied from two directions. An underground cable fault can be isolated and repaired without cutting power to any of the buildings.
Ed
[ November 24, 2003, 06:17 PM: Message edited by: Ed MacLaren ]
britt,
It would be similar to the sketch below, except that I've only shown a few outlets.
There is a medium voltage ring feeder supplying the padmount transformers for the various buildings at our local university. Each transformer is supplied from two directions. An underground cable fault can be isolated and repaired without cutting power to any of the buildings.
Ed
[ November 24, 2003, 06:17 PM: Message edited by: Ed MacLaren ]
- Location
- Massachusetts
Re: Ring Mains or Ring Circuits
A couple of things I can add from reading a non-US forum.
The typical ring circuit in England is fed by one 30 or 32 amp over current device.
The wire size is roughly equal to a 14 AWG.
The plugs themselves (at least some I do not know if all) have fuses in them like this.
Ring circuits UK style.
A couple of things I can add from reading a non-US forum.
The typical ring circuit in England is fed by one 30 or 32 amp over current device.
The wire size is roughly equal to a 14 AWG.
The plugs themselves (at least some I do not know if all) have fuses in them like this.
Ring circuits UK style.
karl riley
Senior Member
Re: Ring Mains or Ring Circuits
I have followed extensive discussion of ring circuits on a non-US forum. There is some strong opinion from UK electricians that the circuit design was a mistake and was due to cost-saving after ww2. Both hot and neutral is ringed. If the neutral is lost somewhere it will not be detected. Or the hot. This can put an overload on some conductors which are sized according to the assumption that current will be shared by both directions on the ring. The overload can be dangerous.
From my area of responsibility a break in the ring also means unequal, non-cancelling currents in hot and neutral with consequent net current magnetic fields.
I think it is a paralleled circuit.
Karl
I have followed extensive discussion of ring circuits on a non-US forum. There is some strong opinion from UK electricians that the circuit design was a mistake and was due to cost-saving after ww2. Both hot and neutral is ringed. If the neutral is lost somewhere it will not be detected. Or the hot. This can put an overload on some conductors which are sized according to the assumption that current will be shared by both directions on the ring. The overload can be dangerous.
From my area of responsibility a break in the ring also means unequal, non-cancelling currents in hot and neutral with consequent net current magnetic fields.
I think it is a paralleled circuit.
Karl
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Ring Mains or Ring Circuits
Karl
But the fault with the UK ring is the fact that the ring shares 1/2 the total current of the OCPD this allows for the failure of the circuit if any break in the circuit were to happen. I think with the breaker rated to protect the wire even if this happened would be safe other that the voltage drop would go up the circuit would be still protected. This is why I don't understand why the NEC will not allow for parallel wires under 1/0 when it is only for voltage drop and not for incresing the current capacity of a circuit?
Karl
But the fault with the UK ring is the fact that the ring shares 1/2 the total current of the OCPD this allows for the failure of the circuit if any break in the circuit were to happen. I think with the breaker rated to protect the wire even if this happened would be safe other that the voltage drop would go up the circuit would be still protected. This is why I don't understand why the NEC will not allow for parallel wires under 1/0 when it is only for voltage drop and not for incresing the current capacity of a circuit?
Re: Ring Mains or Ring Circuits
karl:
A ring circuit would work as parallel circuit since the current would split and flow down two paths to an outlet. So, I won't object if you call it a parallel circuit.
However, it does not meet the NEC requirements for parallel conductors. See Don's post above. The two paths (conductors) would not follow the same path, and they would not be the same lenghth. The result is that the current would not split evenly down the two paths.
Steve
karl:
A ring circuit would work as parallel circuit since the current would split and flow down two paths to an outlet. So, I won't object if you call it a parallel circuit.
However, it does not meet the NEC requirements for parallel conductors. See Don's post above. The two paths (conductors) would not follow the same path, and they would not be the same lenghth. The result is that the current would not split evenly down the two paths.
Steve
charlie
Senior Member
- Location
- Indianapolis
Re: Ring Mains or Ring Circuits
If the conductors are #12 and fed from a 20 ampere OC device, how is this a Code violation? If the circuit is opened or tripped, the entire circuit is open. If an open were to occur on either the phase or grounded conductor, it would not be overloaded.
This is outside my area of expertise but I don't see a big problem. I see a very big problem if you fed the circuit from both directions with separate OC devices or used a 40 ampere OC device on #12 wire.
If the conductors are #12 and fed from a 20 ampere OC device, how is this a Code violation? If the circuit is opened or tripped, the entire circuit is open. If an open were to occur on either the phase or grounded conductor, it would not be overloaded.
This is outside my area of expertise but I don't see a big problem. I see a very big problem if you fed the circuit from both directions with separate OC devices or used a 40 ampere OC device on #12 wire.
Re: Ring Mains or Ring Circuits
But I share the same oppinion as you, that there is no code violation. and it is not a parallel circuit IMO.
Charlie, if the circuit were opened after the breaker it would still be energized (see Ed's sketch). That is the appeal of the circuit. If the braker were opened then it would be de-energized.
But I share the same oppinion as you, that there is no code violation. and it is not a parallel circuit IMO.
karl riley
Senior Member
Re: Ring Mains or Ring Circuits
Steve, yes, I agree this would be a prohibited parallel circuit by NEC.
Charlie, the conductors are the equivalent of #14. UK electricians report overheated conductors when there is a break in one of the ring circuit conductors when the break occurs closer to one end of the ring. Now all the current from most of the ring outlets has to go back the long way, since it cannot be shared by the broken portion of the ring. Since the #14 size is based on sharing both legs of the ring, overloads can take place. These breaks will normally remain undetected unless the overheating is noticed.
Karl
Steve, yes, I agree this would be a prohibited parallel circuit by NEC.
Charlie, the conductors are the equivalent of #14. UK electricians report overheated conductors when there is a break in one of the ring circuit conductors when the break occurs closer to one end of the ring. Now all the current from most of the ring outlets has to go back the long way, since it cannot be shared by the broken portion of the ring. Since the #14 size is based on sharing both legs of the ring, overloads can take place. These breaks will normally remain undetected unless the overheating is noticed.
Karl
karl riley
Senior Member
Re: Ring Mains or Ring Circuits
Dereck, we are writing in real time! Tell me why you think it is not a parallel circuit. It seems self evident to me. But maybe I am missing something. From any one point at an outlet, the current from that load splits and goes back both ways, and is joined on both ends.
Karl
Dereck, we are writing in real time! Tell me why you think it is not a parallel circuit. It seems self evident to me. But maybe I am missing something. From any one point at an outlet, the current from that load splits and goes back both ways, and is joined on both ends.
Karl
Re: Ring Mains or Ring Circuits
Look at it from a different perspective. Let say we closed the phase and neutral ring conductors downstream from the breaker before it reached any load devices. You would only have a single conductor attached the breaker and neutral bus, like a lolly pop if you will.
As far as using a 14 AWG wire on 20-amp device, the solution is simple, 12 AWG.
I know we can go round-and-round on this, but it is just my oppinion.
I concur with Don's point of view. For it to be a parallel circuit the cables need to terminate from point-to-point like a feeder circuit from a main to a sub-panel.
Look at it from a different perspective. Let say we closed the phase and neutral ring conductors downstream from the breaker before it reached any load devices. You would only have a single conductor attached the breaker and neutral bus, like a lolly pop if you will.
As far as using a 14 AWG wire on 20-amp device, the solution is simple, 12 AWG.
I know we can go round-and-round on this, but it is just my oppinion.
roger willis
Member
- Location
- Texas
Re: Ring Mains or Ring Circuits
Karl, you are correct. It is a parallel circuit and is a code violation.
Roger
Karl, you are correct. It is a parallel circuit and is a code violation.
Roger
Re: Ring Mains or Ring Circuits
Are cars on an oval race track moving in parallel?
Are cars on a .25 mile drag strip moving in parallel?
If the conductors are protected at their listed ampacity and we eliminate spurs what would be wrong?
Let's forget the "what if there is a break scenario", in any wiring method a fault, break, or other calamity can be dangerous.
Now for fun, lets protect a #12 conductor ring circuit with two 20 amp breakers on the same phase. Yes I know this puts the ocpd's in parallel and is a violation of 240.8. but look at the loading that could be achieved.
Roger
[ November 25, 2003, 12:16 PM: Message edited by: roger ]
Are cars on an oval race track moving in parallel?
Are cars on a .25 mile drag strip moving in parallel?
If the conductors are protected at their listed ampacity and we eliminate spurs what would be wrong?
Let's forget the "what if there is a break scenario", in any wiring method a fault, break, or other calamity can be dangerous.
Now for fun, lets protect a #12 conductor ring circuit with two 20 amp breakers on the same phase. Yes I know this puts the ocpd's in parallel and is a violation of 240.8. but look at the loading that could be achieved.
Roger
[ November 25, 2003, 12:16 PM: Message edited by: roger ]
roger willis
Member
- Location
- Texas
Re: Ring Mains or Ring Circuits
Roger, Anytime there are two paths for current to flow from the source to the load and back to the source, that is conductors in parallel. It doesn't mean that they have to lay side-by-side.
Another thing that no one has brought up is the fact that this has made a big loop. That loop is a coil, and that coil has inductive and capacitive reactance and will be resonant at some frequency. This could possibly generate noise in the system as it would be able to sent and receive like an antenna.
Roger
Roger, Anytime there are two paths for current to flow from the source to the load and back to the source, that is conductors in parallel. It doesn't mean that they have to lay side-by-side.
Another thing that no one has brought up is the fact that this has made a big loop. That loop is a coil, and that coil has inductive and capacitive reactance and will be resonant at some frequency. This could possibly generate noise in the system as it would be able to sent and receive like an antenna.
Roger
Re: Ring Mains or Ring Circuits
Thank you all for your learned discourse. Thanks Ed for the diagram which was my main interest. Iwire it is my understanding that the cord caps and some receptacles are fused to protect the lamp and appliance cords which we don't do since the Code allows 16AWG to be protected on a 20A ckt.
Thank you all for your learned discourse. Thanks Ed for the diagram which was my main interest. Iwire it is my understanding that the cord caps and some receptacles are fused to protect the lamp and appliance cords which we don't do since the Code allows 16AWG to be protected on a 20A ckt.
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