Modifying ungrounded circuit

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Old 07-20-16, 08:21 PM
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Modifying ungrounded circuit

I know that modifying or extending an ungrounded circuit is not allowed.

Does "modifying" also include removing part of, but not the whole circuit? For example, if there are three receptacles on an ungrounded circuit, can the third one be disconnected from the first two and abandoned? Or would doing any work such as that be "modifying" and require a replacement of the total circuit?
 
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Old 07-20-16, 08:36 PM
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You cannot extend an ungrounded circuit but the word modify is so vague that it could mean almost anything. As such I don't recall ever seeing the prohibition against "modifying" in any electrical code.

In my opinion removing a part of an ungrounded circuit would NOT be contrary to code. However, eliminating the receptacle or light or whatever at the end of the run MAY be a code issue depending on exactly what is eliminated and where it is located. For example, code dictates that any space along a wall must be within twelve feet of a receptacle. If you alter this spacing by eliminating a receptacle you have created a code violation.
 
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Old 07-20-16, 08:41 PM
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2014 NEC has made it easier to ground an ungrounded circuit. Now instead of going back to the panel (or main ground within 5 feet) you can go to the nearest grounded circuit. Of course in the end all code is local so consult your AHJ.
 
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Old 07-20-16, 09:09 PM
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In the case I'm thinking of, there are about five places where there's an ungrounded baseboard receptacle directly beneath a newer, grounded receptacle on a different circuit. So it wouldn't create a receptacle spacing violation. I'm mainly just trying to clean things up, since this circuit manages to get its way into half the rooms in the house, and it's bugging me.

Although you do bring up another question, Ray. Maybe more appropriate for a different thread? I saw that NEC 250.130 allows tying into another grounded branch circuit, like you said. If I wanted to do this (which I can't think of a spot in my house where I would, but talking hypothetically)... Can you just run green THHN or bare copper from the receptacle to a junction box with the nearest grounded circuit? Or does the grounding conductor need to be somehow protected, enclosed, sheathed, etc? Or at least kept in close proximity to the old cable, for identification purposes?

And, if you had a reasonably close grounded branch circuit, wouldn't it make just as much sense to abandon the old cable and run all new cable off of the other branch circuit?

Sorry if this is all a little more hypothetical. I've been trying to understand more of the "whys" behind electrical work versus just the "hows."
 
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Old 07-21-16, 05:53 AM
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Replacing worn out receptacles with like kind is permitted. Replacing a light fixture with a different style of choice (subject to wattage versus circuit capacity) is permitted.

An ungrounded circuit may be upgraded piecemeal. However grounded receptacles may not be installed unless they are grounded according to code which may involve a separately run ground wire, or unless the receptacles have ground fault interrupter protection and are so labeled.

If the "upstream half" of an ungrounded circuit is decommissioned, the orphaned "downstream half" may be hitched up as-is to a modern grounded circuit but another preexisting ungrounded circuit may not be extended in the form of having the orphaned section hitched up.

A separately run ground wire does not qualify the circuit to be extended. A separately run ground wire does not have to follow the current carrying conductors for the circuit.

A separately run ground wire needs to be protected from physical damage. (So does a Romex cable installed to modern code.)

Don't blithely hook up to the nearest modern branch circuit in order to abandon old wiring. Certain bathroom and laundry and kitchen circuits must stay dedicated to those areas or rooms. Also you don't want to accidentally end up with one circuit serving two rooms both of which are likely to have heavy electrical usage that would consistently trip the breaker.

Given an old ungrounded receptacle directly below a receptacle on a modern grounded circuit, the old receptacle might as well be removed and a blank cover plate installed. You may need to splice the incoming and continuing wires to keep the old circuit energized to other receptacles and lights until those can be rewired.
 

Last edited by AllanJ; 07-21-16 at 06:21 AM.
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Old 07-21-16, 09:56 AM
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That makes sense about not tapping into dedicated circuits.

Regarding piecemeal upgrades, then, it is acceptable to run new NM from the panel to a junction box, and then connect it to the old cable with no ground wire? So long as the receptacles served by that circuit are still two-prong or GFCI protected?

And regarding the protection from damage, I'm unfamiliar with THHN applications and have never worked with it. I've only seen mention of running it in conduit. What I'm confirming is that THHN must be run in conduit to protect from damage, even in a wall, whereas NM cable can be run in walls without conduit.
 
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Old 07-21-16, 11:48 AM
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THHN for ground only may be run in walls with out further protection. The wall is the protection. This is an exception because it is not normally a current carrying conductor. Current carrying conductors on the other hand must always be in a raceway such as a conduit or cable sheath for reasons other then just protection.
 
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Old 07-21-16, 12:52 PM
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there are about five places where there's an ungrounded baseboard receptacle directly beneath a newer, grounded receptacle on a different circuit.
This doesn't address all your concerns, but I ran into the same problem when rewiring my house, what to do with the old receptacles.
I didn't have 5 places, only about 2 or 3 where I considered abandoning the old cable or leaving the receptacles.
I chose to install a new receptacle next to the old in a separate box, maybe 6" away.
I also purposely didn't change some receptacles in the house (installed new 2-prong receptacles), I figured the chances of needing to plug in a grounded device in those areas was unlikely.
 
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Old 07-21-16, 03:27 PM
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Thanks for the clarification on that, Ray.

Handyone, I'm a little confused. You mean you left the old receptacle and added a new one as well? Or you abandoned the old one and wired a new one next to it?
 
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Old 07-21-16, 04:21 PM
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Both my ungrounded old circuit and the new circuit can be used. I didn't want 2 circuits in one box so I moved the new box a little away from the original.
It wasn't necessary to keep the old receptacles, but in my case it didn't hurt anything and was easier. The old and new receptacles are mostly hidden behind sofas and beds and will most likely be used for clocks and vacuum.
 
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Old 07-21-16, 05:32 PM
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Ah, I understand now. Yes, that's pretty much what had been previously done here.

My issue/concern is with the circuit itself, that it's just way too much on said circuit. It's a 15A circuit with two hallway lights, three ceiling fan/light combos, outdoor porch lights, a whole house fan with a 1/3HP motor, and then a half dozen or so receptacles throughout the house.

So I'm looking to decommission some of those redundant receptacles, to eliminate the potential for overloading. And then probably try to get the house fan off on its own circuit too.

I apologize that we kind of got sidetracked onto the grounding topic, it was more of a curiosity on my part.
 
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