Upgrading old radial 15A circuit to ring circuit.

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  #1  
Old 05-11-05, 08:19 AM
JonH
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Upgrading old radial 15A circuit to ring circuit.

I have bought an older home that's about 40+ years old. There is no grounding on the receptacles, and the wiring is ad hoc and old. Having done some reading, it sounds like a ring main/ring circuit is the best way to rewire the outlets but I'm a little confused about some technicalities.

If a typical household wiring is 15A, a 15A breaker with 14AWG wiring is sufficient for that circuit, right?

- So how come it's recommended to use a 30A breaker with a ring circuit?
- If ring circuits are so common these days, then how come a typical service panel has mostly 15A breakers?
- Is it common practice to use exclusively ring circuits to wire rooms in the house (i.e. 1 ring circuit for a livingroom, another ring for basement recroom etc.).

Sorry if this doesn't make much sense, I'm still trying to sort out the details in my head.

Thanks in advance!

- Jon.
 
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Old 05-11-05, 08:22 AM
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Are you from the UK?
 
  #3  
Old 05-11-05, 08:24 AM
JonH
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Helps if I give a location, doesn't it? I'm in Canada, so 110V.

- Jon.
 
  #4  
Old 05-11-05, 08:43 AM
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I don't think you need to convert your circuits to ring circuits. If they're all radial now you're asking for lots of work. Unless every circuit is daisy-chained you're going to have a fun time turning the circuits into ring circuits. You just need to run a supply from the (same) breaker to the last outlet on the circuit.

Why do you want to convert to ring circuits?

As far as I know you certainly do not want to put a 30 amp breaker on any circuit that has any length of 14 awg wire. The only thing I can think of that will be helped by converting your circuits the way you describe is a lessening of lights dimming when you turn on a high-load device on the circuit somewhere.

I say it's not worth the conversion, IMO.
 
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Old 05-11-05, 08:52 AM
JonH
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Yes the house is currently all radial. I figured since I was redoing all the circuits for grounding, I might as well upgrade all the circuits to rings so it can handle higher loads. But I guess that's not really necessary.

I've got a few more questions, but I'll save it for a different thread.

Thanks again!

- Jon.
 
  #6  
Old 05-11-05, 10:26 AM
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I was not aware that Canadian Elec Code permits Ring Circuits. The US elec code does not.
 
  #7  
Old 05-11-05, 11:19 AM
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As far as I know the Can code is similar to ours, numbered differently is the major difference.
 
  #8  
Old 05-11-05, 11:48 AM
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The circuits would not be able to handle higher loads. You're still bound by the 80% of the breaker's ampacity for loads lasting 3 or more hours; up to 100% for intermittent loads.

For 14 awg that means 12 amps continuous and 15 amps intermittent.

You'd just notice less dimming of other appliances on that circuit when something with a high-demand is also plugged into that circuit and turned on.
 
  #9  
Old 05-11-05, 12:32 PM
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It sounds like you've been reading the wrong DIY sites.

You cannot use ring circuits in either the US or Canada. If you want to upgrade to more power, the way to do it is to add circuits. These will all be 'radial' circuits protected with the appropriate breaker.

As a bit of background: Ring circuits are common in the UK. In the UK, the rules are quite different, and as a result the various components that you would use in a circuit are different. For one, the permitted OCPD for a given wire size is about double what it would be in North America, based upon the assumption that the current flow will be evenly distributed between the two ring directions. For another, all of the appliance cords are fused, so thin little cords to lamps are properly protected, rather than depending upon the main circuit OCPD. Voltages are higher, and thus currents tend to be lower.

Since current can flow in either direction through the ring, the effective result is that the wire cross-section is doubled. This reduces voltage drop to appliances at the far end of the ring.

Personally, I don't like the idea of ring circuits: the OCPD could let the wire overheat if the load didn't balance, slight imbalances in termination resistance could result in net circulating current flow and significant emf, a circuit that will work but will be overloaded if one of the ring terminals fails.

-Jon
 
  #10  
Old 05-11-05, 01:36 PM
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Ring circuits are not permitted in Ontario. WE use NM cable same as USA. It has a slightly differnt name though NMD for dry locations and NMW for wet locations.
 
  #11  
Old 05-11-05, 03:25 PM
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Cool info, Winnie.

Makes sense, too. I wondered what the advantage of ring circuits was.

Wouldn't it be cheaper to run double the thickness of wire radially, anyway? Not that one can put 15 amp receptacles on a 30 or 40 amp breaker
 
  #12  
Old 05-12-05, 05:34 AM
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"Radial circuit", "ring circuit...." not terms that I've run across before. I'm assuming that "radial" is the normal residential wiring found in general purpose and lighting circuits where a hot and neutral wire start at the panel and go from one device to the next, with or without pigtails.

What's a "ring circuit" and how is it configured?
 
  #13  
Old 05-12-05, 06:06 AM
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A ring circuit makes a complete ring back to the panel. It starts and finishes at the panel. They use a breaker or fuse on each side.
 
  #14  
Old 05-12-05, 06:18 AM
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I suppose the phone wiring in the house I grew up in could be described as a ring circuit. It ran as follows: NID--Jack--Jack...Jack--Jack--NID. I was told that was so if there was a break in the line anywhere, all phones would still work.

The house was built (by my father) in 1978, but I'm not sure whether he ran the phone cables. Was this a common practice then? It was, of course, the standard four wire phone cable.
 
  #15  
Old 05-12-05, 07:51 AM
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Ring configurations are common for all sorts of electrical and communciation circuits. Power transmission lines are almost always arranged in concentric rings around cities so that any single line break will not cause an outage. Computer and telephone networks also usually use rings for redundancy. I have seen phone lines run this way before although I wouldn't call it common. I have actually disconnected a telephone ring because it was causing problems with a modem.

It's really just a confusing overkill for residential application, I think. Personally if wiring in my house fails, I want things to stop working so I know there's a potentially dangerous problem. When a transmission line goes down, it gets noticed. A smoldering electrical fire in a bedroom wall might not be noticed until it's too late.
 
  #16  
Old 05-12-05, 10:33 AM
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Racraft said,
A ring circuit makes a complete ring back to the panel. It starts and finishes at the panel. They use a breaker or fuse on each side.
So this means that after the "last" device neutral, hot, and ground wires would return to the panel and the hot would terminate at a second circuit breaker at the panel? So to work on any given circuit, you'd have to turn off 2 breakers instead of 1? That sounds a bit dangerous.

Steve
 
  #17  
Old 05-12-05, 11:27 AM
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If you lived somewhere where ring circuits were common, it'd be second nature to turn off both breakers.
 
  #18  
Old 05-12-05, 12:09 PM
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Originally Posted by John Nelson
If you lived somewhere where ring circuits were common, it'd be second nature to turn off both breakers.
But are there two breakers on a ring circuit or does both ends of the wire terminate on the same breaker?
 
  #19  
Old 05-12-05, 12:14 PM
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Found some info on ring circuits:

http://www.diynot.com/pages/el/el016.php

Based on the instructions given for connecting to the fuse or breaker, only one fuse/breaker is used for the ring, although that breaker is larger than for the radial circuit...
 
  #20  
Old 05-13-05, 08:36 AM
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Thanks for the link, Mikewu, great link for our European friends. Now I see the light....at least as far as ring vs radial.

Just to recap, radial circuits are not allowed under American or Canadian code.

JonH, I don't know if you've gotten into pulling cable yet, but if the cable insulation is still in good shape, ie. not brittle, you might want to consider providing ground-fault protection by adding a GFCI breaker or GFCI receptacle at the first device box. This gives you the protection you want/ need, without the pain of pulling/ fishing all new cables.
 
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