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cuemaker
10-24-2015, 11:24 AM
Morning,

I replaced a sub power panel in the garage for one with more beakers. In doing that, I somehow failed to ground the box or something. If I touch to machines now, I get a slight buzz in the fingers.

I am missing something. I assume the sub panel is not grounded. How to ground it properly?

This is the box I purchased:
http://www.homedepot.com/p/Square-D-by-Schneider-Electric-Homeline-125-Amp-12-Space-12-Circuit-Indoor-Main-Lugs-Load-Center-with-Cover-HOM12L125C/202495819

MTNGUN
10-24-2015, 11:30 AM
Hopefully someone who is familiar with code will weigh in, but from memory a subpanel should be "grounded" to the main panel, not to an independent ground.

RichR
10-24-2015, 11:46 AM
Since this is a sub panel there should be two bus bars in it. One should have all the ground wires connected to it and it should be
screwed directly to the box so it makes electrical contact. The other should have all the neutral (white) wires connected to it and
it should be electrically isolated from the box. Also check the main panel to make sure the ground is secure. In the main panel, there
should be only one bus bar which has all the grounds and neutrals connected to it.

Rosco-P
10-24-2015, 11:47 AM
Hopefully someone who is familiar with code will weigh in, but from memory a subpanel should be "grounded" to the main panel, not to an independent ground.

That is correct. Also a sub-panel should have the ground and neutral bars physically and electrically separate, bonding jumper should be removed, neutral bar should have the screw that bonds it to the metal case, removed if present.

jmm03
10-24-2015, 11:49 AM
Cue, a subpanel should have a completely separate ground buss in a subpanel and not be bonded to the neutral buss as in the main. The ground buss piece should be available from homey depot where you bought the panel. The neutral in the subpanel should not connect anywhere to the subpanel frame,(via a bonding screw) All the green or bare ground wires should connect to the grounding buss and all the white neutral wires should connect to the neutral buss . A separate ground wire of the appropriate size for your subpanel should run continuously back to the neutral/ground buss at your main which should go to a grounding electrode at your main. I don't have an NEC book handy but if you go online to Mike Holt's website and do a search on grounding you will find the relevant code section. Also check the polarity on any devices you have plugged in or if you accidentally misswired a receptacle . Also,depending on your jurisdiction,they want a separate grounding electrode at the sub. Hope this helps. Jim
(sorry for the repeat info, the other guys are faster typists...)

Mcgyver
10-24-2015, 11:55 AM
I assume the sub panel is not grounded. How to ground it properly?
]

The ground wire coming into the sub panel should connect to the sub panel ground bus bar. The other end of that ground should be to the master panel.

But we don't know what wiring you're got or how you hooked up it up.

Also, I'm not sure it not being grounded is your problem (although make sure it is). Somehow there is a connection between something hot and the machine frame (which should be ground to the subpanel). you're basically touching a live circuit and current is flowing through you to earth ground. it gets a good enough connection and you might not be making any more cues

I'd kill breaker at the main panel, all the breakers in the sub panel, and with a meter start figuring out whats connected to what.

BobSchu
10-24-2015, 11:56 AM
If the sub panel is in a separate building, a separate ground rod should be driven and connected to the subpanel ground system. A difference in electrical potential can develop from different grounding characteristics between the ground in the separate buildings and the floor systems. Your concrete floor (if present) will conduct through your machine if it is a better ground than the one supplied by the Electrical service.

If you aren't completely sure, have an electrician check it out and repair your grounding issues. This is not a good situation to be in if you are getting "tingling" or a "buzz" from your machines. A slight increase in your conductivity caused by sweating or a wet floor could be extremely dangerous or deadly.

Bob

lakeside53
10-24-2015, 12:08 PM
For a separate building sub-panel the later codes now require BOTH an remote ground rod AND a grounding conductor run between the buildings (there are exclusions and a couple of ways to do this so look it up). Check your local AHJ for what pertains to you.

For a "local" sub panel, as explained above ground is from your main panel and the neutral is NOT bonded to ground at the sub-panel case.

cuemaker
10-24-2015, 12:08 PM
Ok, here is a pic of the setup.

I think I have the 3rd wire (bar aluminum line labeled "main" in pic) going to the wrong spot

http://i201.photobucket.com/albums/aa129/xringx/Sub_zpspb9sqhvw.jpg (http://s201.photobucket.com/user/xringx/media/Sub_zpspb9sqhvw.jpg.html)

lakeside53
10-24-2015, 12:11 PM
Is that a 4 wire incoming feed? I can't tell but it looks like 2+G. You need 2 phase wires, a neutral AND a ground if you are going to derive any 120v loads. You cannot do this is you have only 2 wires +ground, and even if a separate building, you cannot repurpose that ground braids as neutral (both ends) and provide a separate ground. Did you just grab the feeder going to the stove and try to substitute a subpanel?

Run a NEW feeder cable - 3W plus G.

BTW.. an OVEN (if allowed by your AHJ) can use (grandfathered) a 3 wire circuit even though it's wired for 4 - like yours is (assuming there a ground wire somewhere). You cannot wire a sub-panel like this And.. where is the OVEN GROUND WIRE? If there is no separate ground wire, the "white" is likely assumed to be connected to ground, not neutral... but investigate to make sure it's simply not just cut off.


If you use aluminum feeder, you must use antioxidant paste on the wires /terminals, both ends.

And.. look at the instruction on the subpanel for the removal of any neutral/ground bonding.

Rosco-P
10-24-2015, 12:13 PM
OMG, your panel wiring reminds of the stuff I saw in Mexico.
No budget for proper electrical connectors?

Is that orange extension cord running out of the bottom of the panel?

kendall
10-24-2015, 12:14 PM
Buy yourself some grommets, trim that feed wire up. If 3 wire, If it's 3 wire, black and white go to the main breaker, ground to ground with neutral and ground busses tied together. If 4 wire, black and red to mains, white to neutral, ground to ground and not tied to neutral. Then throw a ground rod in.

lakeside53
10-24-2015, 12:25 PM
Buy yourself some grommets, trim that feed wire up. If 3 wire, If it's 3 wire, black and white go to the main breaker, ground to ground with neutral and ground busses tied together. If 4 wire, black and red to mains, white to neutral, ground to ground and not tied to neutral. Then throw a ground rod in.

No.. He cannot use a 3 wire (2+G) for this configuration (he has both 120v loads and neutral referenced oven), and no separate ground rod is used if in the same building (residential with no separately derived source).

cuemaker
10-24-2015, 12:27 PM
OMG, your panel wiring reminds of the stuff I saw in Mexico.
No budget for proper electrical connectors?

Is that orange extension cord running out of the bottom of the panel?

No..that is not an extension cord. Just the color of the jacket. It's solid wire.

As for connectors, I didn't put them up top yet as am not done..and I now think I will have to redo. And this is much better than my main box.

Ok, its 3 wire..so that is the first problem.

So go 4 wire, run the main ground to ground in sub, neutral to neutral and hots to hots.

lakeside53
10-24-2015, 12:40 PM
Yes.. and investigate how your oven is connected. If it is truly three wire, your white will need to go to panel ground, not neutral. Take care with this... and make sure it's not messed up at the oven end.

When you rewire it, put ONLY your ground connection on the ground bar; your 120v neutral connections go only to one of the two neutral bars. Although it's usually the default, make sure the neutral bars are not bonded to ground.


What size breaker are you feeding the panel from?

kendall
10-24-2015, 12:46 PM
No.. He cannot use a 3 wire (2+G) for this configuration (he has both 120v loads and neutral referenced oven), and no separate ground rod is used if in the same building (residential with no separately derived source).

I didn't see where he mentioned an attached garage. Also, ground on oven is not hooked up either. I read it as he 'replaced' a box, not a whole new service. If using the old feed, and it's 3 wire, then ground and neutral bars should be tied.


Edit bars should be tied because without 4 wire, the only ground will be to the box itself, which means anything with a ground prong on the plug will become part of the ground plane.

Rosco-P
10-24-2015, 01:03 PM
I didn't see where he mentioned an attached garage. Also, ground on oven is not hooked up either. I read it as he 'replaced' a box, not a whole new service. If using the old feed, and it's 3 wire, then ground and neutral bars should be tied.


Edit bars should be tied because without 4 wire, the only ground will be to the box itself, which means anything with a ground prong on the plug will become part of the ground plane.

It's a sub-panel, don't know what that cable fed before, but it's not suitable to feed a sub-panel which requires a separate neutral and ground conductor.

cuemaker
10-24-2015, 01:08 PM
Still digesting the posts.

Yes, stove is 3 wire for sure. Main service is in the garage, and the sub panel is right next to it.


The first sub panel was installed already when I purchased the house a few years ago. But I have decided to replace/rewire it cause I got tired of crawling around **** to plug and unplug machines.

Main panel is a Cutler Hammer from 1972 when the house was built. Its 200amp service.

I have 1 spot open and I believe a spot that is labeled for something that does not exist. Still have to investigate that.

This is my plan. I will see if I can go get another 2 pole breaker for the main box, move the stove wire back to its original location, and jump from the new breaker using 4 wire.

rdhem2
10-24-2015, 01:19 PM
If outlets to plug machines is the problem, why not just add more outlets. Unless you are more clever then me, you will only run one machine at a time anyway. More receptacles are way cheaper and don't draw any power just by being there. More circuits from a new panel does not cure much if the machine plugged to them is not running.

Just a thought.

cuemaker
10-24-2015, 01:49 PM
If outlets to plug machines is the problem, why not just add more outlets. Unless you are more clever then me, you will only run one machine at a time anyway. More receptacles are way cheaper and don't draw any power just by being there. More circuits from a new panel does not cure much if the machine plugged to them is not running.

Just a thought.


I am way to deep for simplicity here...

OK, I have purchased a 60amp breaker, 15feet of 6/3 4 wire(copper) and the cable lock down thingys...

I shall do my best to make Rosco-P proud of the wire work..I expect to fail

J Tiers
10-24-2015, 02:24 PM
before anything else..... If you get a tingle from machines, there is a problem with the equipment grounding conductors, the green wires. They are not doing their proper job. Possibly one is disconnected, or possibly it is connected to the wrong place.

The green ground wire from the subpanel should go all the way to the main box, and be connected to the grounding bus there. If it is not present, you need one. Then the green wires from the branch circuits off the sub-panel should all go to the bar in the subpanel that is connected to the box.

Trying to put it all in one post....

First, boxes and grounds and neutrals.
A box for a subpanel should have two kinds of multi-wire connector blocks/bars.

One SHOULD be attached to the box somehow (usually by simply screwing it to the box in the provided location per instructions with the box). This is for green equipment grounding conductors ONLY.

The other should be INSULATED FROM the box, and is for the neutral (white wires) ONLY. It will often have a spot where a green screw (usually provided) can "bond" the bar to the box. You do NOT use that screw when using the box as a sub-panel


Second, connections to main box

From the main box you should have a 4 wire cable, sized for the subpanel capacity. There should be the two hot wires, a neutral, and an equipment grounding conductor (EGC).

The neutral and EGC will connect to the SAME ground bar in the MAIN box, BUT will be SEPARATE in the SUB PANEL. The EGC goes to the bar in subpanel that connects to the subpanel box, and the neutral goes to the isolated bar.

The hot wires go to the feeder connections in the subpanel.

Your #6 cable is good to 65 amps at 75C. That's the limit, because most connections are rated only to 75C. The use of 90C cable (which you may have) is simply to allow going through hot areas (like attics) without de-rating.

cuemaker
10-24-2015, 02:55 PM
Mr Tiers,

I only got a tingle when I touched my mill and lathe at the same time... not just one or the other. Also, the mill is a 110 plugged into main breaker box, the lathe is 220 plugged into new sub.

And thankyou.. Same to you Lakeside for the help.. I hope to have it under control soon.

The Artful Bodger
10-24-2015, 02:57 PM
J Tiers, is the EGC in the sub box grounded (i.e. earth stake) locally?

Paul Alciatore
10-24-2015, 03:48 PM
If this is a lot better than the main box, RUN, do not walk, but RUN to get a licensed electrician before you fry someone or burn the house down.

If you absolutely insist on doing it yourself, go to Lowe's or another local lumber yard and buy a good book on electrical wiring. AND READ IT 100% BEFORE PROCEEDING.

One more thing, in any case make 1000% sure the grounds are PROPERLY connected FIRST. From a ground rod where the service enters the property, through the meter box, through the main panel, through the aux panel(s), and finally to EVERY outlet or machine. This comes absolutely first.




No..that is not an extension cord. Just the color of the jacket. It's solid wire.

As for connectors, I didn't put them up top yet as am not done..and I now think I will have to redo. And this is much better than my main box.

Ok, its 3 wire..so that is the first problem.

So go 4 wire, run the main ground to ground in sub, neutral to neutral and hots to hots.

Rosco-P
10-24-2015, 03:52 PM
If this is a lot better than the main box, RUN, do not walk, but RUN to get a licensed electrician before you burn the house down.


+1 Paul.
Wanted to say something similar.

Do the right thing before you kill someone like the wife or kids.

cuemaker
10-24-2015, 04:04 PM
I have actually had 2 electricians look at and give me estimates so I can increase the number of breakers. Neither had an issue with the main panel or the sub panel I just removed and gave me quotes to put in a new box.

Its just not neat inside

J Tiers
10-24-2015, 06:13 PM
Mr Tiers,

I only got a tingle when I touched my mill and lathe at the same time... not just one or the other. Also, the mill is a 110 plugged into main breaker box, the lathe is 220 plugged into new sub.

And thankyou.. Same to you Lakeside for the help.. I hope to have it under control soon.

So you were between a presumably properly earthed machine and a questionable one on new circuits. OK makes sense, still suggests a problem with ground/earth wire.


J Tiers, is the EGC in the sub box grounded (i.e. earth stake) locally?

Not as a rule, no has not been. Never in the same building, with an outbuilding supplied from same service, it may or may not be accepted by local authority. The one and only earth is at the "service", where the power enters the building. This avoids earth currents theoretically, although they may still exist.

A local ground should never be used as a substitute for a connection back to the service.

I like it for an outbuilding, there are sound reasons for it, and I think more recent codes have it. But local authorities may not be using the latest code, it has to be accepted by law.

lakeside53
10-24-2015, 08:12 PM
I didn't see where he mentioned an attached garage. Also, ground on oven is not hooked up either. I read it as he 'replaced' a box, not a whole new service. If using the old feed, and it's 3 wire, then ground and neutral bars should be tied.


Edit bars should be tied because without 4 wire, the only ground will be to the box itself, which means anything with a ground prong on the plug will become part of the ground plane.


He's adding a new sub-panel. He cannot use a 3 wire system as he want to derive 120v circuits. He must have a 4 wire. You do not tie the neutral and ground bar together on a sub panel. Anyhow... he's now bought the correct cable and can wire it correctly.

kendall
10-24-2015, 10:50 PM
He's adding a new sub-panel. He cannot use a 3 wire system as he want to derive 120v circuits. He must have a 4 wire. You do not tie the neutral and ground bar together on a sub panel. Anyhow... he's now bought the correct cable and can wire it correctly.

original post:


Morning,

I replaced a sub power panel in the garage for one with more beakers. In doing that, I somehow failed to ground the box or something. If I touch to machines now, I get a slight buzz in the fingers.

I am missing something. I assume the sub panel is not grounded. How to ground it properly?

This is the box I purchased:
http://www.homedepot.com/p/Square-D-by-Schneider-Electric-Homeline-125-Amp-12-Space-12-Circuit-Indoor-Main-Lugs-Load-Center-with-Cover-HOM12L125C/202495819


Note he says "I replaced"
If the original box was fed with the 2 conductor + ground wire shown in his picture, then bridging the ground and neutral bars would have given him exactly what had with more spaces.

mickeyf
10-24-2015, 11:09 PM
If I was an electrical inspector, and saw what you showed in the photo, I would have your power disconnected immediately until an real electrician had required it entirely.

If I were an insurance agent and saw that, I would never insure you again, and I certainly would not pay out when your house burned down, even if it was the fireplace that did it, not the wiring.


RUN, do not walk, but RUN to get a licensed electrician before you burn the house down.

There are places to save money, and doing your own wiring can be one of them - I do all my own wiring. But for the love of all things holy, understand what the code is, and why it is, what the principles of power wiring and safety are before you take this on. You really wanna be a Darwin award winner? Jeez.

lakeside53
10-24-2015, 11:39 PM
original post:




Note he says "I replaced"
If the original box was fed with the 2 conductor + ground wire shown in his picture, then bridging the ground and neutral bars would have given him exactly what had with more spaces.



Makes no difference. It's still illegal and unsafe. Copying or adding to prior mistakes is not a defense. You don't get to use your grounding conductor as a neutral return for 120v circuits except under a very limited circumstances (if allowed by the AHJ) - like for grandfathered stoves where rewiring is not practical. Even with that. you don't get to add more 120v loads.

I had to correct a mess last week where installers 25 years ago had connected a microwave outlet between the stove 50 amp 240v supply and ground. Easy fix but required a convoluted new home run back to the panel.

J Tiers
10-24-2015, 11:49 PM
I WAS gonna say, cut him some slack, at least he's asking....... I WAS gonna do that.

Then I took a good look at the panel picture. OK, the feeder is not connected, and it's the wrong type anyhow, so hanging down is expected. The red and black wires are kinda short, and hard to run neatly, I'd strip back and run those better. The rest of it is no worse in terms of technique and neatness than the electricians did who wired a new breaker box in my house before we closed on it (city required it).

So, like I said, I took a GOOD look at the panel......

I see four apparently 2 pole 220V breakers, and a 120 breaker. One of the 220 breakers is wired with a red and a black wire, as it should be. BUT THAT CABLE HAS NO EQUIPMENT GROUNDING CONDUCTOR. Just a neutral. BAD CUEMAKER!

THEN, there is what appears to be a DIFFERENT PROBLEM... I see three apparently identical breakers at left, and EACH ONE HAS A BLACK AND A WHITE WIRE GOING TO IT. Now if those breakers were GFCI breakers, they would have a wire to the neutral bus, but they don't, so they are just 2 pole breakers. THE WHITE WIRE IS ALWAYS TO BE GROUNDED TO NEUTRAL BUS, IT NEVER EVER IS A HOT WIRE. But you HAVE it connected as a hot wire, and you did not even MARK it as a hot wire. BAD CUEMAKER!

BOTTOM RIGHT CABLE seems to be OK.

So far, out of 5 load side wires, and the input, the only good setup is the 120V at bottom right. All the others have code violations, some serious.

This project is off to a very bad start.

If you are going to do the work yourself, then at least get a basic house wiring book and follow what it says. Or hire it done.

Ohio Mike
10-24-2015, 11:52 PM
Makes no difference. It's still illegal and unsafe. Copying or adding to the prior mistakes is not a defense.

Absolutely.

To take this a step further... Just because a machine was wired up before and works doesn't make it correct! I now check every bit of wiring on machines I purchase. A couple of years ago I picked up a machine that was awful. Many things wrong, first was three phase feed with 4 conductor SO with some NEMA single phase locking connector on it... At least they use the ground pin correctly... Second hit was a 120v control but with no transformer installed. They just tapped one leg on the contactor for the control and tied the other side to the ground in the case. One rule, trust no one.

The Artful Bodger
10-25-2015, 12:51 AM
Here is something we found in the field (Afghanistan) a 440V distribution cabinet and yes it is alive!

https://farm7.staticflickr.com/6032/6280571769_4459b4a2bd.jpg

flylo
10-25-2015, 01:55 AM
Cuemaker will make sure it's done right, I have no doubt. That's why he asked the original question.

cuemaker
10-25-2015, 08:43 AM
Ok, you all are big meanies.. I just followed how the last box that was installed..Have questions, will reply to Mr. Tiers reply with em..

cuemaker
10-25-2015, 08:53 AM
I see four apparently 2 pole 220V breakers, and a 120 breaker. One of the 220 breakers is wired with a red and a black wire, as it should be. BUT THAT CABLE HAS NO EQUIPMENT GROUNDING CONDUCTOR. Just a neutral. BAD CUEMAKER!

Ok, the cable with red and black wire is the original stove wiring. Its a 3 wire. I have moved it back to main panel and hooked up the exact same as the furnace is, which is also 3 wire. I assume its all original from 1972. Not sure what else, other than running a new cable, I can do with that.




THEN, there is what appears to be a DIFFERENT PROBLEM... I see three apparently identical breakers at left, and EACH ONE HAS A BLACK AND A WHITE WIRE GOING TO IT. Now if those breakers were GFCI breakers, they would have a wire to the neutral bus, but they don't, so they are just 2 pole breakers. THE WHITE WIRE IS ALWAYS TO BE GROUNDED TO NEUTRAL BUS, IT NEVER EVER IS A HOT WIRE. But you HAVE it connected as a hot wire, and you did not even MARK it as a hot wire. BAD CUEMAKER!

So is the issue that the wires are white or that they need to be 4 wire instead of 3 wire? Should I run 4 wire, or mark the whites as hot with red tape? Rest of your assumptions were correct. Not GFCI, all double pole breakers.


BOTTOM RIGHT CABLE seems to be OK. Yeah?!?!?!?!?!?

J Tiers
10-25-2015, 09:40 AM
Yes the issue is white wire. The ends should at least be marked as not white. White is neutral and ONLY neutral.

For a 220only circuit, two hots and an EGC is fine. But no white wires please. This is more difficult with cable, since you normally find 2 wire with ground as white and black.

Any inspector will ding you for that immediately.

Since you are working with the stove wire, it needs to be brought up to code. If you left it alone it could be grandfathered. Not if you work with it.

kendall
10-25-2015, 09:41 AM
Makes no difference. It's still illegal and unsafe. Copying or adding to prior mistakes is not a defense. You don't get to use your grounding conductor as a neutral return for 120v circuits except under a very limited circumstances (if allowed by the AHJ) - like for grandfathered stoves where rewiring is not practical. Even with that. you don't get to add more 120v loads.

I had to correct a mess last week where installers 25 years ago had connected a microwave outlet between the stove 50 amp 240v supply and ground. Easy fix but required a convoluted new home run back to the panel.

While I won't argue safety, I will say that if the original box was approved and safe at the time of installation, it would be no less safe to duplicate the installation with the new box. It wouldn't pass inspection, but would be just as safe as the original box. Looking at the picture, with the lack of clamps, I'd say inspection wasn't on his list of things to be done.
That said, I've always been the type to say if you are doing it, do it right.

10KPete
10-25-2015, 10:21 AM
The difference is 'repair' vs. 'replacement'. Repair would be changing a bad breaker; no need to bring up to current code.
Replacement of the whole box means you bring it up to current code.

Pete

lakeside53
10-25-2015, 11:52 AM
Yes, exactly.

And were there any 120v loads in the original box "as inspected"? I doubt it... And.. did it even have an inspection at all or was it a 1970's homeowner or shadetree install?

Cuemaker - drag your stove out and check how it is wired. Stoves were all originally three wire even they derived a small current from 120v for controls (one leg to ground), but they still have to be grounded. IF (IF) they are using the white wire to "ground" to the "neutral"... urgh.... minimally you need green tape on the ends (more recent codes - 2008?- say the entire wire must be green or bare). WRT Jerry's above - you can in most jurisdiction get way with simply wrapping black tape on the last few inches of white when it's repurposed on a 240v circuit.

Rosco-P
10-25-2015, 11:56 AM
The difference is 'repair' vs. 'replacement'. Repair would be changing a bad breaker; no need to bring up to current code.
Replacement of the whole box means you bring it up to current code.

Pete

In most states, repair still requires a permit and an inspection. This job would require a permit, which a homeowner can pull for himself. IMHO, what the inspector would say will be very interesting.

cuemaker
10-25-2015, 01:04 PM
Stove....Stove wire went back to what has to be the original break, and the white wire went back to the only open spot available, right next to the furnace white wire.

I am not going to mess any original main panel except to install the new breaker and 4 wire based on instructions given here. Replacing the box is under discussion.

Is taping the white wires with red or black electrical tape an acceptable fix?

MaxHeadRoom
10-25-2015, 01:07 PM
Conductors can be identified by the correct colour tape etc, at each termination point.
Max.

garyhlucas
10-25-2015, 01:19 PM
Extra credit question. WHY must the neutral and grounding conductors be separated for a sub panel. "Its a code requirement" is not the correct answer.

BobSchu
10-25-2015, 02:01 PM
Stove....Stove wire went back to what has to be the original break, and the white wire went back to the only open spot available, right next to the furnace white wire.

I am not going to mess any original main panel except to install the new breaker and 4 wire based on instructions given here. Replacing the box is under discussion.

Is taping the white wires with red or black electrical tape an acceptable fix?

There is no code requirement for colors for current carrying conductors other than they cannot be white (or grey) or green. Either black or red would work great for color coding white wires where they emerge from the sheath in NMB, but just about any color would be legal.

The Artful Bodger
10-25-2015, 02:10 PM
There is no code requirement for colors for current carrying conductors other than they cannot be white (or grey) or green. Either black or red would work great for color coding white wires where they emerge from the sheath in NMB, but just about any color would be legal.

Is white not the neutral and hence one of the 'current carrying' conductors?

Rosco-P
10-25-2015, 02:30 PM
Extra credit question. WHY must the neutral and grounding conductors be separated for a sub panel. "Its a code requirement" is not the correct answer.

Any stray current on the neutral would then return on the ground and pass through all devices along the way back to the main panel. If there is ever a break in the neutral you wouldn't know it as you would still have a return path for the current.

pstemari01
10-25-2015, 03:11 PM
....

A local ground should never be used as a substitute for a connection back to the service.

I like it for an outbuilding, there are sound reasons for it, ...

+1. The connection back to the main service is what ensure that breakers will pop when something shorts to ground. A local ground spike in the outbuilding ensure that the local ground is equipotential to the protective ground.


Sent from my Nexus 6 using Tapatalk

BobSchu
10-25-2015, 04:07 PM
Is white not the neutral and hence one of the 'current carrying' conductors?

No, technically the white is the neutral, which should only carry the unbalance of the load. In a perfect situation, the voltage of the circuit will be dropped across the loads. But nonetheless, the neutral for code purposes, is not considered a "current carrying conductor". It is referred to as the "grounded conductor"- not to be confused with the "grounding conductor".

Bob

garyhlucas
10-25-2015, 06:06 PM
Any stray current on the neutral would then return on the ground and pass through all devices along the way back to the main panel. If there is ever a break in the neutral you wouldn't know it as you would still have a return path for the current.

Close. Actually the ground conductor would share the neutral load all the time, as it is in parallel with the neutral. Which ever one is the better conductor will carry most of the load. So there could be lethal potential on the ground conductor, and it could arc and cause a fire.

I grew up in the electrical business, starting working every day during the summer when I was about 10 or 12. Dad always taught me the theory behind everything we did as we worked. When I graduated high school I was already running a crew wiring chemical plants and such. Best electrician I ever met, but his career ended when he had a stroke at 48. He's tough though, I was visiting with him today. 86, has a pacemaker, a heart valve, broke both hips, had one replaced completely, broke his pelvis, and one ankle, and 4 ribs, two torn rotator cuffs. The energizer bunny, just keeps going and going.

Paul Alciatore
10-25-2015, 06:51 PM
The answer to this is that there are a number of problems that could develop where keeping these two conductors (ground and neutral) separate is very desirable. Both of them are connected to the ground rod connection at the building's service entrance. But they serve different purposes.

On a 115 V circuit the neutral does carry the same, full current that the hot wire carries. But, the neutral is at "ground" potential. Now consider a situation where the neutral becomes disconnected at the local breaker box. When a device is plugged into the outlet or otherwise connected and is turned on, it will not operate. But all the wiring inside that device will become energized with the full 115 V or close to it. And that disconnected neutral wire will also become energized at that same 115 V potential. Thus the neutral can become a shock hazard.

Another consideration is the Voltage loss in the current's return through the neutral wire. All wire has some resistance and that includes the wire used for neutrals. So, there will be some Voltage drop across that return path and the neutral wire at the device will not actually be at true ground potential. It can be several Volts or even more above that level. If the neutral is used as a ground or the ground is used as a neutral, then the "grounded" case of the device will not be truly grounded. And if it comes in contact with another, true ground, sparks may fly. These sparks could ignite any flammable gas or other substance in the vicinity. This is a FIRE hazard. Thus a separate ground path that does not normally carry any current and that really is at true ground potential is required. If the device fails in a manner that energizes the case, then excessive current will flow and the breaker WILL trip quickly.

There are other failure modes where a separate ground wire is a life or property saver. Thus, the code requires a separate path back to the single point where the ground rod is connected to the incoming service to add additional safety and prevent many of these problems. These problems can exist between the main and the sub panel so the ground and neutral conductors are kept separate there.




Extra credit question. WHY must the neutral and grounding conductors be separated for a sub panel. "Its a code requirement" is not the correct answer.

J Tiers
10-25-2015, 07:43 PM
Neutral IS a current-carrying conductor. The EGC (ground wire) IS NOT a current carrying conductor. Reasons are close to what Paul said, but in addition there is the concept that if there is already a voltage drop in the ground wire, and then you ADD fault current, the total voltage drop may begin to be hazardous, or certainly be more than wanted.

Also, the idea with the EGC is that everything connected to it is at the same voltage. Clearly this is not so if there are pre-existing voltage drops in it. Those voltage drops with right environment conditions might cause corrosion etc that damages the low resistance ground connection.

But, actually, the real answer is in fact that "the code requires it". You really do not need to know more than that.

As for marking wires, the marking is intended to be more-or-less permanent. Inspectors have differing opinions as to what that means. Tape might be OK for one, another might require some other means that is less likely to come off over time.

lakeside53
10-25-2015, 07:53 PM
No, technically the white is the neutral, which should only carry the unbalance of the load. In a perfect situation, the voltage of the circuit will be dropped across the loads. But nonetheless, the neutral for code purposes, is not considered a "current carrying conductor". It is referred to as the "grounded conductor"- not to be confused with the "grounding conductor".

Bob

That is only in the case of a shared neutral between 2 "out of phase" phase conductors; typical in a 3 wire+G romex. With neutrals run separately - like in 12-2+G romex.. the neutral carries the same current as the phase conductor. it gets more complicated when multiple neutrals are joined in a junction box, but...

And... it is defined as a current carrying conductor by NEC.

BTW.. Since 2008... (you area may not be using this yet, but most are) if you are using a 3 wire+G romex , both breakers must now have a common trip tie. PIA when one circuit trips and the other does also, but that's the code and it makes sense. I rarely run common neutrals now.