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ground and and neutral bonding for parallel 14/3 romex runs

Posted by dgeist (My Page) on
Sat, Dec 24, 11 at 13:49

I have a bathroom fan with multiple loads built in (nightlight, fan, 60w light, and humidistat). It's configured to use a single 14/2 feeder that utilized state changes at the switch to power the fan/humidistat on and off right now. The nightlight is currently unpowered.

Alternately, the ability exists to have each light and the fan/humidistat controlled separately, but it would require more conductors (basically a pair of 14/3s or a 14/2 and a 14/3). The schematic in the instructions covers the switched conductors, but it shows all the neutral and ground conductors simply "running into each other" as a junction. I know that electrically, the whole system should have all the neutrals and grounds bonded, but I don't know if it's proper to do it at the fixture, the switch box, both, or simply only use one conductor for ground and one for neutral in the pair of wires. The parallel romex runs to and from the same place would allow for any combination.

Thanks.
Dan


Follow-Up Postings:

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RE: ground and and neutral bonding for parallel 14/3 romex runs

You need a copy of at least 'wiring simplified' so that you understand wt grounds and neutral do ad how they are connected.


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RE: ground and and neutral bonding for parallel 14/3 romex runs

I'm familiar with ground and neutral conductors, but if I have two grounds and two neutrals from the same branch in the same boxes on both ends, I just need to know where the neutral and ground bonds should be (yes, I know the N and G are not bonded to each other in the branch).

Dan


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RE: ground and and neutral bonding for parallel 14/3 romex runs

The grounded condutor (neutral) and the equipment ground (ground) are connected together in exactly ONE PLACE in any structure and that is at the service disconnect.


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RE: ground and and neutral bonding for parallel 14/3 romex runs

(sigh) I'm not doing a good job explaining this... The ground and neutral conductors will stay separated. I need to know if (in the two NM wires each having neutral and ground conductors) that are used for this, where is the proper place to bond the neutral to the other neutral and the ground to the other ground, switch side, load side, both, or just use one ground and one neutral from the pair for the whole system.

I don't THINK I can have a NM wire with only hot leads in it without running it in a conduit with the wire that DOES have the ground and neutrals. That's why I'm asking where respective neutral and ground pairs should be connected.

Thanks (and hopefully it makes sense this time).
Dan


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RE: ground and and neutral bonding for parallel 14/3 romex runs

Your first problem is stop using the term "BONDING" here. It is not what you are doing and lending to the confusion.

Every piece of NM cable in your circuit will have a ground. You connect all those grounds together. PERIOD, END OF STORY. If you have metal boxes, you also BOND (in this case it is correct) the box to the common ground. Any device (receptacles, switches, fans, heaters) are also bonded to the common ground on the cable feeding them.

The NEUTRALS similarly get connected together. This means that all the white wires will be connected. A natural never runs through the switch (in your case).
There is one case (a loop down to a switch from a box with the power feed) where there isn't a neutral in the cable going to the switch. You are however these days required to remark the white wire some other color (other than white,gray or green).

You should not usually have NM in a conduit EITHER. I have no idea what you're talking about there.


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RE: ground and and neutral bonding for parallel 14/3 romex runs

"The NEUTRALS similarly get connected together."

Not exactly.

Neutrals from seperste breskers dhould NEVER be combined.

A neutral travels with a hot, ad is the return path for current on that hot.
Multi-wire circuits are the sole exception for multiple hots sharing a neutral. They use opposite legs of the 120 V to make sure the shared neutral cannot be overloaded by the two hots.

For conventional circuits fed from a single pole breaker neutrals are NOT combined among branch circuits.

You need a copy of "Wiring Simplified' or a similar book to learn the basics from.


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RE: ground and and neutral bonding for parallel 14/3 romex runs

I believe he is talking about a SINGLE branch circuit.


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RE: ground and and neutral bonding for parallel 14/3 romex runs

Let me try and translate :-) .

I think he has something like this...

* A single circuit 14/2 going to box A.

* Two switches in box A.

* A 14/2 and a 14/3 going from box A to box B to carry two switched loads and one non-switched load.

So you've told him that all the grounds get connected together at both box A and box B.

But I think he is asking what to do with the neutrals - do you connect them together in box A, box B, or both?


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RE: ground and and neutral bonding for parallel 14/3 romex runs

I'm familiar with ground and neutral conductors, but if I have two grounds and two neutrals from the same branch in the same boxes on both ends, I just need to know where the neutral and ground bonds should be (yes, I know the N and G are not bonded to each other in the branch).

Dan


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RE: ground and and neutral bonding for parallel 14/3 romex runs

"I'm familiar with ground and neutral conductors, but if I have two grounds and two neutrals from the same branch in the same boxes on both ends"

No, you are not "familiar with ground and neutral conductors" just from the questions you are asking.


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RE: ground and and neutral bonding for parallel 14/3 romex runs

Brickeyee, I appreciate your candor, but your complaint is with my terminology, not my meaning. I'll endeavor to clarify if you try to stop being condescending.

Blame android for the double-post. It's one branch with line feeding the switch box, 3 switched loads and 1 unswitched. All loads are in the same fixture. All grounds tied to the branch ground. All loads in phase. Do the neutral conductors in the NM 14/3 lines get connected to each other at both ends or only at the switch?

Dan


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RE: ground and and neutral bonding for parallel 14/3 romex runs

I think what Dan is trying to explain is that he needs a 14/5 connection to the fan unit - four hots, one neutral, and one ground.

He'd like to connect this using 14/3 and 14/2 NM from the switch box to the fan assembly.

If code allows this, should he connect the two separate respective NM grounds, and separately, the NM neutrals together at each end?

If this is allowed by code, then he really doesn't need parallel neutrals, but should have grounds in both runs - I don't know - can't fathom why this would be unsafe, but I am not knowledgeable enough on code issues to answer this. Just trying to help him get a safe and knowledgeable answer here.


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RE: ground and and neutral bonding for parallel 14/3 romex runs

Just to correct my above reply - That should read: He'd like to connect this using two 14/3 NMs from the switch box to the fan assembly. ...makes the math work out right! : )


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RE: ground and and neutral bonding for parallel 14/3 romex runs

I spoke with a family member at holiday dinner who does industrial control systems and electrical/mechanical facilities design. He had the following thoughts regarding this issue:

- 99% of power distribution systems he'd seen use only ever use fan-out for return-path conductors, no additional connections are used commonly, even on parallel lines on the same phase/circuit.

- the 1% that DO have multiple conductors connected at multiple points are for critical control systems with redundant power requirements and have special monitoring, design constraints, etc. and none are common in residential.

- Although the NEC may have something to say (which he wasn't sure), most common troubleshooting methodologies would not support connecting the multiple neutrals anywhere except the switch box since if there was a conductor failure, the load would positively indicate the failure and the single tie at the switch location would likely speed troubleshooting.

- In some cases (although not in this case), the operation of GFCI would be affected by connecting diverse neutrals on the same branch, even with adjacent loads (i.e. if there's a GFCI receptacle inline on one of the load lines). This factor is in play here since it's my master bath and will be GFCI protected.
Maintaining good circuit design for support-ability makes sense to me, so unless there IS a stipulation by the NEC, I think that's the way I'll go.

Hopefully I didn't use the wrong terms for anything this time :)

Dan


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RE: ground and and neutral bonding for parallel 14/3 romex runs

The right way to do this would be to run conduit. Then you could run as many hots as you need (respecting the conduit fill rules), and keep everything together. What might be acceptable to the inspector is to run additional cable alongside the existing, keeping them as close together as possible. Connect the grounds of the two cables together at both ends. You don't actually need a second neutral; it's all still the same circuit, and the current capacity is (presumably) still limited by the circuit's 15A breaker, so the one 14 ga. neutral is sufficient.

I'd mark the ends of the additional cable with different colors (blue, yellow, brown, etc.) to reduce confusion in the future.


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RE: ground and and neutral bonding for parallel 14/3 romex runs

", I appreciate your candor, but your complaint is with my terminology, not my meaning. I'll endeavor to clarify if you try to stop being condescending. "

The learn what you are trying to talk about and stop guessing.

"industrial control systems"

Low voltage power limited control wiring does NOT follow the same rules as branch circuit wiring.
It has g\greatly relieved requirements since the power limited circuits are not a significant fire source (think thermostat and doorbell type circuits in residential uses).

If you need to control multiple functions in a single fixture you can use 3 conductor cables, and have two separately switched feeds and a single neutral.

If you use separate 2 conductor cables you do not connect the neutral together at the fixture, but each hot feeds a portion of the fixture, and returns the current from that portion on the neutral in the cable with the hot.


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RE: ground and and neutral bonding for parallel 14/3 romex runs

if the power source..the feed line( hot and neutral) enter the switch box on the wall..
lets call this case 1.
the hot lines to the all 4 switches. there is 1 hot line that feed all 4 switches.
the grounds tie together..
the whites also tie together..same phase guys..the source is ONE BREAKER..ONE HOT..ONE NEUTRAL..

care for case 2 or more??

case 2..the feed is to the fixture..Hot/N/ Gnd..
four 14/2 to the switch. in this case the Gnd tie together.
the H and N don't the N is actually an H..color it something other than white.

case 3..yes it can get worse if your not lost yet
feed the box with 2 breakers of opposite phases..not a double pole breaker either..all the load are 120V..
this is where you have to keep the gnd tied..
the neutrals for the same breaker tied together but not to the other breaker..think GFIC/Arc fault..

if you're lost..especially in case 1 or 2..why are you wiring? hire someone..its safer..for you now and someelse whom might work on it later.

-dkenny


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RE: ground and and neutral bonding for parallel 14/3 romex runs

dkenny: not lost, but amused :)

I fall into case 1, so no worries, there. I'm just trying to imagine someone intentionally feeding two sides of a fairly low power bathroom fixture from different breakers/phases (technically, wouldn't that be a violation of NEC on bathroom branch circuits...).

brickeyee: I understand what you're saying and agree on the low voltage applications, but I wasn't talking about low power (or even DC) applications.

Appreciate the feedback, all. I'm set for now.

Dan


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RE: ground and and neutral bonding for parallel 14/3 romex runs

"I understand what you're saying and agree on the low voltage applications, but I wasn't talking about low power (or even DC) applications.

Most "industrial control systems" are low voltage ad power limited to get relief form the NEC rules about wiring methods and components.

Safety lockouts for machinery, machinery control circuits (on-off and speed control), elevator controls, lift controls, measuring equipment like digital readouts, temperature monitors and controls, pressure monitors and controls, etc.

No on wants to use 14-2 for control circuits (especially when 48 V and a few hundred miliamps is about the most required.

It is a world away from 120/240 V power wring, or even high leg (stinger) commercial building wiring.


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