Ring circuits from another thread

[roger]

Karl, this is not to put you on the spot but I must ask, in a true ring circuit, no spurs, all loads with no faults, and conductors sized to carry the load individually (being even across hot and grounded conductor, no imbalance) how would we have a high magnetic field if the rules of AC going and coming (conductors side by side or even twisted if in a conduit) would cancel itself.

Let's use a single load dead center of the ring for the conversation.

This is a sincere question.


Roger

[ August 18, 2003, 09:44 PM: Message edited by: roger ]

 

[ryan_618]

Re: Ring circuits from another thread

Roger: This is also a sincere question...how are ring circuits not parrellel circuits?

[ August 18, 2003, 09:55 PM: Message edited by: ryan_618 ]

 

[hurk27]

Re: Ring circuits from another thread

A parallel circuit would be one that has two conductors ran in parallel to allow each conductor to handle half of the total current of the circuit. The load would be connected at the end of the run, not in the middle like a ring circuit. A ring circuit is more for voltage drop and would be protected by a breaker that would have a rating that would protect just one of the two conductors, even if one were lost the breaker would still safely protect the remaining conductor. I Don't see why 310.4 exception 2 could not be changed to include ring type circuit's as if fits all the criteria, except that it is not a control circuit. Unless you want to say that you know when the drive is lit when the lights are on.
Even if you ran parallel conductors to over come voltage drop as long as the circuit protection is only sized for one of the conductors it would be safe.

 

[hurk27]

Re: Ring circuits from another thread

I forgot the question that was asked in the first place.

There would be no heating in a ring circuit because the current would still seek the return path of the same send conductor. if there was 10 amps from the short direction of the ring back to the panel and 5 amps from the long direction back to the panel (total circuit amp's 15) the corasponding neutral will have the equal amp's.
I mean the short neutral will have the same 10 amps on it that the short ungrounded conductor does and it will be 180 deg. out of phase with the ungrounded conductor. So it would cancel out the magnetic heating.

 

[karl riley]

Re: Ring circuits from another thread

Roger, I am answering here as well as on the other thread. Yes, if all conductors including the redundant neutral were run together, no magnetic field. Just like having neutral connected to the EGC out in the circuit, no magnetic field if the EGC runs with the conductors without touching anything metal. I assumed the neutral was going to be run outside the other conductors. In the UK the rings are loops and it is an EMF problem there.

It's still a violation of 310-4 I believe. I know redundancy has reasons, but so does the NEC. By the way, I don't mind any contrary opinions, so no-one be hesitant about telling me they think I'm all wet. Just give me good reasons!

Karl

Karl

 

[karl riley]

Re: Ring circuits from another thread

Hurk, you wrote yours at the same time I was writing mine. I believe the diagram showed only the neutral in a ring but the ungrounded conductor normal.

Karl

 

[hurk27]

Re: Ring circuits from another thread

Get in sinc Karl.

LOL

Just kidding but here in the U.S. we do use the ring circuit but of course it's the power co. that can get away with it.

 

[lrollo]

Re: Ring circuits from another thread

I guess I dont understand, are you calling a "Ring Circuit" a circuit which is fed at two ends. Kind of liked a supervised circuit in a fire alarm circuit? The circuit leaves the breaker, hits the devices and returns the other end to the same breaker? Is this legal in a circuit other than a fire alarm?

 

[iwire]

Re: Ring circuits from another thread

Originally posted by lrollo:
The circuit leaves the breaker, hits the devices and returns the other end to the same breaker? Is this legal in a circuit other than a fire alarm?

You got it exactly, and many people consider this a parallel circuit.

If it is a parallel circuit it would be a violation.

It is used in other countries for dwelling wiring.

 

[roger]

Re: Ring circuits from another thread

Leaman, as Bob says, you are correct in your assumption.

In the overseas version it is used to allow say 16 amp wire to serve a 32 amp circuit.

The diagram below is from Ed MacLaren member #19 here

One problem with the overseas version is that the break in the wire shown in Ed's diagram would leave 16 amp wire potentially carring a much heavier load. If we used full rated wire this wouldn't be a concern. Another problem with the overseas version is the use of "spurs" a tap to an outlet outside of the ring.

The circuit is argued to be parallel by some but I see it as a loop.


Here's a fun thought, if we could parallel fuses (OCPD's) we could serve the loop with #12 and connect to two 20 amp fuses which would provide 40 amps to the total sum of the loads and not overload the conductors, although, we would have to give some thought to even dispersion of conductor lengths and loads. Of course fuses in parallel can't be argued, and this isn't really the reason for using a ring circuit.

Roger

[ August 20, 2003, 09:09 PM: Message edited by: roger ]

 

[lrollo]

Re: Ring circuits from another thread

Thanks for clearing that up. I guess I will pass on using this type of wiring method but heres a thought; I havent seen too many 20 amp breakers that will allow you to install two conductors on its lug. I know to do that it must be listed for use with more than one conductor. Also, if I am interpreting the code correctly, a panel can't be used as a junction box; so the pigtailing of the two conductors to tie under one lug of the breaker would be a violation. I guess one could use the "piggy back " breaker and put one end on one breaker and the other on the other part of the breaker, being it occupies the same bus.

 

[iwire]

Re: Ring circuits from another thread

Roger, This can not be a parallel circuit.

310.4 Conductors in Parallel.
Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and larger, comprising each phase, neutral, or grounded circuit conductor, shall be permitted to be connected in parallel (electrically joined at both ends to form a single conductor).

Because we know that conductors that are not directly connected to each other are not connected.

Bob

[ August 20, 2003, 09:38 PM: Message edited by: iwire ]

 

[lrollo]

Re: Ring circuits from another thread

P.S. the piggy back would pose a problem though if one couldnt tie the handles together.

 

[roger]

Re: Ring circuits from another thread

Bob, thanks I forgot, shame on me.

Leaman, most SQ D & Cuttler Hammer breakers 15 to 30 amp and #14 to # 10 are lisred for two conductors. I will post the information tomorrow if some body else doesn't before then.

Roger

 

[iwire]

Re: Ring circuits from another thread

One thing with the use of this in other countries is that I believe the outlet is fused so you will not have a small gauge appliance cord with 32 amps feeding it.

 

[dereckbc]

Re: Ring circuits from another thread

Quit thinking inside a box Yankee’s. UK uses 220 volts (6600 VA)! They use it to supply something like a lighting 30-amp- circuit to cover a large area like the first floor of your home or other occupancy. The loop does not have to originate at the breaker panel, it can terminate downstream at the first device just like a tap. IT HAS MERIT!

 

[karl riley]

Re: Ring circuits from another thread

Roger, if you look at Ed's diagram that you showed, after the break occured in the hot, the two ring cables back to the panel will be carrying unbalanced hot and neutral currents, hence net current heating from the magnetic fields generated. The reason for 300-3(b) is to prevent this heat buildup. Probably 310-4 for the same reason.

Of course, if the breakers were GFCI they would trip, so you couldn't have that safety protection and get you "uninterupted service". Interruptions have their function: you have to fix the problem. Emergency services might overrule this.

Karl

 

[roger]

Re: Ring circuits from another thread

Karl, in Ed's diagram we only have one load as it is shown which would be equal current between the one hot path and dual neutral paths. So here it would be questionable as to whether a GFCI breaker would pick it.

Roger

 

[karl riley]

Re: Ring circuits from another thread

So you have both hots and both neutrals running to one GFCI?

Karl

 

[roger]

Re: Ring circuits from another thread

Karl, yes the ring would be landed on one breaker regardless of GFCI or not. My mention of connecting to two breakers would no doubt be a violation of 240.8. I could see in some controlled situations where the parallel OCPD could have advantages.

I could also see where in heavy starting and jogging loads, the loop (ring) would make the conductors happy to have a partner in the heating effects.

Roger