UK wiring style

[zbang]

Let's get a couple of things out of the way-
Is the breaker rated for two wires under "one screw"? Probably. (are there two on the breaker or is it pigtailed?)
Is the breaker of an appropriate size for the wire?
There are multiple devices, so this is not a pure case of parallel conductors.
I also assume that all three leads are following the entire ring.
I don't think you get anything out of 300.3(b).

When you get past all of that, it's kind of weird practice for the US, but I can't see something that prohibits it. Or more to the point- is it unsafe? If so, why?

 

[Rodolphe Schomberg]

Quote=102 /1445108

Quote=102 /1445108

Just inspected a job done by a gentleman from the UK. The circuits were run from the overcurrent device to a receptacle, then looped through 6 more rececptacles than returned to the overcurrent device effectively creating a loop of the current carrying conductor. He did the same thing with the grounded conductor. It did not pop the breaker, but I refused it based on the NEC. I told him I would get code sections if needed and am just starting to dig into the specifics. What is the thought process behind this? Is it because the UK operates from a 240 volt system typically. He was not happy with me since he says it works just fine.

No BKR trip means the CKT is properly grounded, There is no short circuit present.
mean that it is wired on the same pole. Since the wiring protection must be evident at the electrical panel, the return wire should be clearly identified at the panel. For it not to trip it would have to be a Square D breaker or similar, approved for double connection; or it might have been fed from the same pole, which is a safety hazard. In any case the loop double feeds the circuit, lowering the wiring resistance.
The EI was right not to pass it on two grounds:
1- It is not UK here, the American technician would not understand the wiring technique. Wiring technique in America does not for a loop.

 

[Besoeker]

I also assume that all three leads are following the entire ring.

Obviously the live and neutral have to. We have just single phase 230V live and neutral for most residences.
Clause 543-032-09 of BS7671 requires the protective conductor (earth/ground) to run in the form of a ring having both ends connected to the earthing terminal at the origin of the ring.

 

[dicklaxt]

I forgot to say when we used it in the offshore living quarters and/or decks it was two independant coduits running on opposite outside walls/platforms so a damaged section or fire could easily be isolated and the breaker be reclosed.

dick

 

[Smart $]

...
I don't think you get anything out of 300.3(b).

...

Assuming a physical loop, all circuit conductors are not in the same raceway, cable, etc.

To be compliant, the raceway, cable, etc. would have to contain both hots and both neutrals.

As mentioned, feeding through device terminations is a splice. So it is parallel wiring.

 

[jeremysterling]

I agree with the others that say this is non-compliant parallel conductors.

I agree with iceworm that the fix is very easy.

 

[ronaldrc]

I don't understand all the hype about the UK being 240 volts
Most of the residential dwellings in the USA are 120/240 volts single Phase
this has nothing to do with the nominal voltages.

This is the reason I always liked a inspector that has a lot of experience in all
phases of electrical work. They are able to think out of the box.

When the CMP with the NEC. made the, No parallel anything under 4/0 rule.

I don't think there intentions where to keep electricians from doing things like
we are discussing here.

I think they knew if they needed 60 ft. of 6/3 w/grd for a range and didn't have
it handy and had to make a trip to the hardware they would not hesitate to run
two runs of 10/3 in parallel for a range.

I think this should be the inspectors call using common sense.

Ronald

 

[tom baker]

Perhaps if the NEC allowed it we would see this wiring method more often.
Let me rephrase my question, what section does not allow it (ring wiring)?

 

[PetrosA]

I would say that 310.4 doesn't allow it as it doesn't comply with any of the exceptions or descriptions for allowed parallel wiring methods while it does meet the definition of conductors in parallel.

 

[lavacano]

Well lets get this straight parallel conductors are being used only for increasing ampacity of 2 smaller conductors (i.e. 2x 4/0 for 400a). There are no other reasons to run a circuit in parallel other than to increase ampacity of the circuit or feeder.

By this logic, I restate that as long as the breaker is sized for the wire it should fly.

Also to those on the opposing logic, if he were to pigtail his wire inside the panel down to 1 conductor entering the breaker would it still be considiered parallel to you?

 

[ronaldrc]

I think the reason most would use this circuit would be because
of voltage drop.I do not know of any NEC. section that would not allow it.
Each feeder contains a returning conductor to cancels any eddy currents.

Ronald

 

[PetrosA]

Well lets get this straight parallel conductors are being used only for increasing ampacity of 2 smaller conductors (i.e. 2x 4/0 for 400a). There are no other reasons to run a circuit in parallel other than to increase ampacity of the circuit or feeder.

By this logic, I restate that as long as the breaker is sized for the wire it should fly.

Also to those on the opposing logic, if he were to pigtail his wire inside the panel down to 1 conductor entering the breaker would it still be considiered parallel to you?

Only Exception No. 1 allows wires smaller than 1/0 to be run in parallel, and a ring circuit doesn't meet that exception:

310.4 Conductors in Parallel.
(A) General. Aluminum, copper-clad aluminum, or copper
conductors of size 1/0 AWG and larger, comprising each
phase, polarity, neutral, or grounded circuit conductor shall
be permitted to be connected in parallel (electrically joined
at both ends).
Exception No. 1: Conductors in sizes smaller than 1/0
AWG shall be permitted to be run in parallel to supply
control power to indicating instruments, contactors, relays,
solenoids, and similar control devices, or for frequencies of
360 Hz and higher, provided all of the following apply:
(a) They are contained within the same raceway or
cable.
(b) The ampacity of each individual conductor is sufficient
to carry the entire load current shared by the parallel
conductors.
(c) The overcurrent protection is such that the ampacity
of each individual conductor will not be exceeded if one
or more of the parallel conductors become inadvertently
disconnected.

 

[lavacano]

Only Exception No. 1 allows wires smaller than 1/0 to be run in parallel, and a ring circuit doesn't meet that exception:

But the only reasoning to run a ckt in parallel is to increase its ampacity. If not increasing ampacity it should not, for any intent or purpose be considered a parallel circuit.

 

[PetrosA]

But the only reasoning to run a ckt in parallel is to increase its ampacity. If not increasing ampacity it should not, for any intent or purpose be considered a parallel circuit.

No, Exception No 1 is clearly there for when redundancy is needed. Because of when it allows for that redundancy, I think it's safe to say that ring circuits are not considered a necessary type of redundancy for branch circuits.

 

[gadfly56]

No, Exception No 1 is clearly there for when redundancy is needed. Because of when it allows for that redundancy, I think it's safe to say that ring circuits are not considered a necessary type of redundancy for branch circuits.

If redundancy is required, Exception 1 is exactly how NOT to wire a circuit. Fire alarm circuits are wired Class A for just such a reason, and the code prohibits running the return leg in the same cable or raceway as the supply leg. Although it's an Appendix A note in the 2007 edition, you are supposed to maintain 1 ft vertical or 4 ft horizontal separation of supply and return, except in the vicinity of the FACP.

Does anyone know the history of the prohibition? How exactly is it different if I loop the branch circuit around the building and place the last receptacle 2" away from the panel, or land the hot and neutral back in the panel, assuming the circuit breaker is listed for 2 conductors under a terminal?

By the way, if you carefully read the excerpt from the code as requoted by PetrosA, it says you may parallel 1/0 and larger, but it doesn't forbid smaller. Everything not forbidden is permited, unless there's more before or after that section that I don't remember.

 

[Rick Christopherson]

Unless there is only one device on the circuit, this is not a parallel circuit. Even if there was only one device, the purpose of the rule about parallel conductors does not apply. It is not being done to allow conductors to be smaller than the circuit ampacity.

300.3.B isn't even close to applying. All of the conductors are in the same raceway. Are you suggesting that you can't branch a circuit in 2 different directions because the conductors would no longer be in the same raceway?

There is nothing technically wrong with a ring circuit. You guys are just resisting it because it is foreign to you. Technically it is superior to a linear circuit. That doesn't mean I would waste the wire to create one, but there is nothing wrong with its existence. And there is nothing in the NEC preventing it.

 

[frenchelectrican]

One thing Besoker is right on the spot related to the ring circuit and I will give you a quick example what we are refering to this.,

The typical conductor size is 1.5mm2 ( little smaller than 14 AWG ) and with the 32 amp OCPD breaker ( it used to be fuse only legit on very old installment ) and run them in loop format I know you guys keep saying parallel.,, Yeah I know it is parallel format and we have the power point ( recpetales or socket ) that have fused plug to limit to 13 amp or less.

But that is slowly dropping out of the system due if the ring loop some reason loose the " loop " connection, it can get the 1.5 conductor seriously overloaded.

So therefore few electricians are going with conventail format which it called radial format it casue less issue with it.

By the way ., I know you may say something about France., Well the Ring circuit loop is NOT legit in France so we stay with radial format just like you guys in the state / providices

So techally wise it is not really legit per NEC the item it will kill it is parallel conductor size as few members posted which that is correct.

( the other loop hole I know is if from factory set up as part of equiment then it may get away with it. )

Merci,
Marc

 

[PetrosA]

If redundancy is required, Exception 1 is exactly how NOT to wire a circuit. Fire alarm circuits are wired Class A for just such a reason, and the code prohibits running the return leg in the same cable or raceway as the supply leg. Although it's an Appendix A note in the 2007 edition, you are supposed to maintain 1 ft vertical or 4 ft horizontal separation of supply and return, except in the vicinity of the FACP.

Does anyone know the history of the prohibition? How exactly is it different if I loop the branch circuit around the building and place the last receptacle 2" away from the panel, or land the hot and neutral back in the panel, assuming the circuit breaker is listed for 2 conductors under a terminal?

By the way, if you carefully read the excerpt from the code as requoted by PetrosA, it says you may parallel 1/0 and larger, but it doesn't forbid smaller. Everything not forbidden is permited, unless there's more before or after that section that I don't remember.

So maybe my assumption is wrong. If not for redundancy, why would you run a circuit according to exception 1?

My understanding of the exception is that if you run smaller than 1/0 in parallel, it must meet those conditions. How does that allow you to run smaller than 1/0 if it doesn't meet those exceptions? If you read it to mean that running parallel conductors under 1/0 in general is allowed, but if they feed those items mentioned in exception 1 they must meet those requirements, doesn't that become a design specification, which the NEC isn't supposed to be?

Personally, I don't see anything wrong with a ring circuit in theory. The problem I see is that it's not a wiring style that electricians here would easily identify in use if they came across it in the field. The term "branch circuit" is a visually descriptive name based on the wiring model we use (a tree) and a ring circuit doesn't fit in that model. For instance, in a ring model you wouldn't be allowed to branch out from the ring. Instead, you would have to expand the ring by running two cables from the tap point to the next device and back. Ultimately I think the best argument against using ring circuits in the US is that it would violate 110.8 (only suitable wiring methods are mentioned) and potentially 110.12 (workmanlike manner). Ring circuits are NOT mentioned in the NEC, so are therefore not suitable, and installing one would be unworkmanlike because you'd be violating 110.8.

 

[roger]

The problem I see is that it's not a wiring style that electricians here would easily identify in use if they came across it in the field.

The same could be said of newer electricians and Ungrounded Deltas but, they are still out there and in use.



Roger

 

[Besoeker]

I don't understand all the hype about the UK being 240 volts
Most of the residential dwellings in the USA are 120/240 volts single Phase
this has nothing to do with the nominal voltages.
Ronald

A significant difference between UK and US wiring is that here (and, as far as I know, most of EU land) uses single phase 230V for dwellings. The centre tap arrangement is not used. Everything operates at 230V. Wiring in dwellings is usually flat twin and earth (your ground) cable. Live, neutral, and earth. Brown, blue, and bare copper with an outer sheath which is grey - I don't know if the grey is mandatory but I've never seen any other colour used. I haven't seen metallic conduit used in decades.