Looped Power Feed?

[mbrooke]

How is this different from any circuit. The fact that it is a loop does not change the ability to fault. If you brake the loop then why bother having a loop circuit. Now you have two circuit or one circuit spliced in the panel. That would be what Trevor was talking about earlier. The loop is not necessary

Correct, but a 40amp breaker will allow current to flow for a longer time then a 20amp breaker, hence why thinner cords need a fuse inside the cord cap.

In this day and age with copper being pennies on the dollar compared to right after WWII, rings no longer have the advantage they once had.

FWIW Id argue however that the only rule restricting a ring is the parallel conductor rule.

 

[romex jockey]

How is this different from any circuit. The fact that it is a loop does not change the ability to fault. If you brake the loop then why bother having a loop circuit.

Current returns via two paths to the ocpd, so would fault current

~RJ~

 

[Dennis Alwon]

Guy's I already stated I misspoke. I did not realize you were talking about 2- 20 amp breakers

 

[GoldDigger]

Maybe we can lobby for a 120% rule for two breaker loop circuits. :angel:

 

[kwired]

Maybe we can lobby for a 120% rule for two breaker loop circuits. :angel:

Doubt it, we would get report back stating you can't parallel grounding electrode conductors:roll:

 

[JFletcher]

If you connected line and load of a GFCI to what is essentially the same lines it will not work as intended. Depending on design you may still have voltage at the receptacle but no GFCI protection. But consider that as long as it is tripped - you have opened the "ring circuit"



Those suggesting we land each end of this circuit on separate overcurrent devices - please note I am not in favor of that practice at all for reasons you suggest it is a problem. My only support of such a circuit is if you have a single overcurrent device that is sufficient to protect the conductor size attached to it, the conductor goes out and makes a loop to all the components supplied and returns back to same point of supply. It may or may not be NEC compliant depending on how you interpret 310.10(H), but is in no way ever going to result in a potentially overloaded/overprotected conductor.

I agree. The only way I could possibly see a ring circuit working w/o being a hazard is that the wiring leaving and returning the panel (say 2x14/2 NM) be run thru the same cable clamp/pop-in and then individual conductors be twisted together, wago'd or wirenutted, then pigtailed to ONE breaker (15A in this case). If it were ever NEC approved, perhaps a piece of NM jacket marked "Ring Circuit" slid over the conductors as well. The make-up and marking in the panel would be critical imo to keep a future electrician from doing, say, a panel change, undoing everything, then landing each "leg" of the ring on the same leg of the panel but different OCPD (resulting in double fed double OCPD ampacity) or worse, opposing legs and creating a bolted fault across the mains.

iwire, I hadnt thought of fire, but I'm not sure a ring would make things worse; if you installed 4 7W led lights for a sidewalk fed from a 300W driver, there' still a ton of available current and sufficient voltage to cause a fire. heck, 4-ought steel wool and a 9V battery is an instant fire. I dont know what internal OCP the driver has, and if it had none, under major fault, it would probably let its smoke out before tripping even a 15A breaker.

 

[mbrooke]

If anyone is curious this is how rings and fused plug tops came about:

https://www.google.com/url?sa=t&rct...QOX-49TRDaCODA&bvm=bv.109332125,d.amc&cad=rja


RJ is correct, they came about after a copper shortage and the UK still refuses to ban them.

 

[mbrooke]

Their ring circuits would basically be our #14awg made onto a 30A OCPD twice, or what we'd term double tap...

Ampacity being divisible allowed the lesser conductor(s) to be installed

Originally they'd ring a house twice , keep in mind their voltages are higher, thus magnitudes (their term for ampacity) lower

However, it's easy to see how a compromised 'ring' can cause mayhem , which given their 70 yr old debut as well as building construction is a likely bet

~RJ~

Believe it or not its exactly that. 14 gauge is 2.08mm2 in size and 2.5mm2 is exactly 2.5mm2 in size. The extra .4mm2 gives roughly an extra 1 to 2 amps in current capacity. If 2.5mm2 was put into our code it would come out as 16 amps 60*C, 22 amps 75*C and 27 amp 90*C. 16x2=32 amps. So this is exactly like doing a ring in #14 and putting it on a 30amp breaker.

 

[SceneryDriver]

I did not know you are in NYC. For some reason I thought you were out west.

I used to be. I moved to the NYC area just over a year ago.


SceneryDriver

 

[mgookin]

I used to be. I moved to the NYC area just over a year ago.


SceneryDriver

Welcome to the cool side! :thumbsup:

I've lived my entire life on the East coast of the US but have spent some time on the West coast. It is interesting out there and if I ever have opportunity I'd love to just piddle around out there for a year or so.