# Two subpanel wiring schemes - serious problems?



## Nancy_in_GA (Oct 20, 2004)

I have two subpanels---one installed by an electrician over 20 years ago, and one done this summer by an electrician who retired 20 years ago and has not kept up. So both have only a 3 wire cable to the subpanel (2 hot wires and a ground, no neutral). I *think* this was acceptable in the past? 

The first one is inside my house, and the neutrals from the circuits and all the grounds are hooked into the same metal bar which is bonded to the panel cabinet.  

The second one is in an outbuilding at my mother's house, and the neutrals and grounds are separated---the grounding wires are bundled together and bonded to the panel. This panel has only 3 circuits--lights, one general receptacle, and one receptacle for a fence charger, no ground rod.

I just found out that neither is up to current code, but changing the lead in cable to 4 wire would be a major pita in both cases. So if I'm stuck with the 3 wire cable, which one is better/safer, or should we check into a motel?

I can rewire either or both panels, or add ground rods. 
Nancy


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## agmantoo (May 23, 2003)

I am NOT an electrician. If you are concerned about compliance with the current code then an upgrade is in order. Metal buildings and mobile homes have a greater requirement for the 4 wire systems. If safety is your concern then you could consider installing ground fault interrupters in the kitchen and bath and on outside circuits. There are millions of homes wired as yours.


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## rambler (Jan 20, 2004)

The outbuilding needs a ground rod, but otherwise would be ok. This is a cheap upgrade. It is considered it's own main box, and you bond the ground rod to the nuetral & ground loop in this main box.

The subpanel inside the house I don't understand. Where is your main box located where these subpanels are coming from? If it is in the house, then you really need to run a 4 wire feed to the subpanel. If the main box is out at the pole, then you can wire up the house with a 3 wire feed, and ground to the water pipes & a ground rod. Also consider it it's own main box.

4-wire all the way is liked better, but individual buildings can have 3 wire & ground rod setups; each is considered it's own main panel.

If you have a subpanel in a building that also has the main box, you should be running 4 wire to the sub.

I don't want to get into the ground/ neutral bonding unless we really understand where all of your boxes are located & how each is grounded. There are many wrong ways to do it, & one right way for each situation..... Need to grasp the entire situation first.....

--->Paul


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## Nancy_in_GA (Oct 20, 2004)

I'm sorry, I guess I edited too much out in a effort to keep things short. Probably should have made two separate threads anyway.

The indoor subpanel runs from a main panel in the basement of that house. So I think the question boils down to, do you let the neutral wires for the circuits just dead end in the breaker box (there is no neutral to go back to the main panel), or do you connect them to the grounding wires. It seems to me the safer method is to separate them, because if you tie them to the grounding wires, and there is a fault, any current in the neutral wires would be diverted to the grounding system and you might get a shock when you touch anything on the grounding system. I'm just guessing though.

The outbuilding subpanel runs from the main panel for a mobile home, which is mounted on a pole outside the home. Since the outbuilding has only 3 circuits I thought it didn't need a separate ground rod, and the ground rods for the fence charger are about 30 feet from the building, so I was also afraid two sets of ground rods that close might cause some kind of conflict.

The only reason I even noticed this at all is because I was going to replace the 2 breaker subpanel in the outbuilding with one that has 4 breaker spaces, and I opened the one in the house for the first time ever in 20 years just to see how it was set up.

I think the outbuilding is OK according to old codes, so I'll just leave the wiring the same as it is set up now, when I replace the breaker box.

Things like this don't worry me as much as they should, I guess. I still have a lot of knob and tube wiring left in my house so if I'm going to upgrade, I'll start there.

Thank you.


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## farminghandyman (Mar 4, 2005)

The out building panel should have a ground rod,



> The indoor sub panel runs from a main panel in the basement of that house. So I think the question boils down to, do you let the neutral wires for the circuits just dead end in the breaker box (there is no neutral to go back to the main panel), or do you connect them to the grounding wires. It seems to me the safer method is to separate them, because if you tie them to the grounding wires, and there is a fault, any current in the neutral wires would be diverted to the grounding system and you might get a shock when you touch anything on the grounding system. I'm just guessing though.


The indoor box should be feed with a separate ground and neutral, and some is for the reasons you stated, but I do believe it is better to have the ground and neutrals hooked together, (the neutral is the white wire, and the circuit will not work with out it, the bare wire is the ground, the black goes to the breaker), than leaving the grounds undone, 

but as long as the "ground/neutral" wire coming into the sub panel is solid and tight, there is not IMO a major problem, or no more as in a sense it is jsut like nearly the same as the main disconnect, no it is not current code and has not been for years, but if you have any older 3 wire 220 volt appliances on this box, such as a dryer or and electric range, the ground and neutral is compromised any way, and the two (the neutral and ground), is connected. So to up grade it would need a 4 wire plug and cord changed out and make sure the appliance has no internal bonding. 

Now if the boxes are connected by metal conduit there is a ground path if the conduit connections are tight and solid. And if there is a conduit adding a ground wire should not be a big thing, if that is what one wants to do. Yes a wire assures a path with out the reliance on the conduit and it's connections.

I was talking to my son in law who is a licenced electrician this last week about similar issues on my farm, and in many instances with out all most starting over and completely rewiring the entire farm from scratch, to meet all the new current codes. (have been general contractor for the last 30 years, and have some knowledge of the electrical code, but do not know all the code specifics). 

but here is the catch 22, if you start to change any thing, by code what ever you touch then needs to be brought up to current code, if you don't touch it and if it was wired properly in its day to the applicable code it is legal.

Just like the knob and tube, (NO you can not wire new knob and tube), but if you have it there is no legal requirement to up grade it, as long as it was correctly wired in its day.


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## sammyd (Mar 11, 2007)

You should replace the 3 wire to the sub in your house with a 4 wire. PITA or not.

Neutral is bonded to ground in the main but should not be in a sub so any fault in the wiring will be directed back to the mains ground and not around through your neutral/ground connection in the sub, which may or may not bring on the problems you are worried about.
Leaving the neutrals disconnected will cause the 115V circuits to not work unless for some reason you have the grounds on those circuits hooked up to the load which is certainly not correct.


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## rambler (Jan 20, 2004)

As FHM says, the outdoor box needs a ground rod (you can't have too many ground rods; you can have too few). I had a building or 2 like that as well, but - it's a whole lot better with a ground rod grounding the box. That box would be considered a main panel, and would be wired as such - neutral & ground bonded in the box & fed to a ground rod. I would not want to use 3 prong outlets in this building without a ground rod - likely it was wired for 2 prong recepticals and there is no ground wire at all in the building.

Also, you should have 4 wires running from the main box in your house to the subpanel, and in the sub panel the ground & neutral wires should _not_ be bonded. Doing so presents a lot of shock hazards for various reasons. Not a good thing. The ground wire protects humans from dying. The nuetral wire is a normal part of the electrical circut. The 2 different wires should only be bonded at one location in a building, and directly from there to a ground rod (and water pipes). To bond them together at more than one location sets up loops that can really hurt a person if things go wrong.

Neither of these upgrades should be a real expensive job, you would need to run a 4 wire feed wire from one box to the other & get a proper ground buss in the subpanel. And run a #6 wire out to a ground rod in the out building.

As always, this is just conversation, I'm a simple dirt farmer, not an electrician.

--->Paul


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## Nancy_in_GA (Oct 20, 2004)

sammyd said:


> ...Leaving the neutrals disconnected will cause the 115V circuits to not work unless for some reason you have the grounds on those circuits hooked up to the load which is certainly not correct.


Sammy, if by "leaving the neutrals disconnected" you mean just hooking the neutrals into the neutral bar in the subpanel, but not connecting them to a neutral wire back to the main panel, then come to my barn sometime and see the lights come on.


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## rambler (Jan 20, 2004)

Just a bit more thoughts on it....



Nancy_in_GA said:


> The indoor subpanel runs from a main panel in the basement of that house. So I think the question boils down to, do you let the neutral wires for the circuits just dead end in the breaker box (there is no neutral to go back to the main panel), or do you connect them to the grounding wires.



That would be _very_ wrong, and not really possible. you can't get any electricity without a neutral return path. The hot & neutral wires are needed for the electricity to flow. With only these 2 wires, things will work & you won't notice any problems until they happen - then all sorts of bad things can happen.....

The ground wire ends up going to all metal surfaces you can touch. It is that 3rd rounded prong on tool cords, as well as a green wire on the frame of your fridge, oven, furnace, etc....

If you confuse the ground & nuetral wires, you end up putting electrical potential on _all bare metal surfaces_ throughout your house.........

So, don't do what you said above. That would be real bad. You do not _ever_ want dangling, unconnected wires in a box. (If you meant let the ground wires dangle - that is real bad too, sets people up to get hurt.)

I would want this part re-done by a qualified electrician. It does not sound safe or good at all as you describe, & involves the house where many people can be exposed to hazard. Really would not be very expensive, unless fishing the 4-strand wire is difficult.



Nancy_in_GA said:


> The outbuilding subpanel runs from the main panel for a mobile home, which is mounted on a pole outside the home. Since the outbuilding has only 3 circuits I thought it didn't need a separate ground rod, and the ground rods for the fence charger are about 30 feet from the building, so I was also afraid two sets of ground rods that close might cause some kind of conflict.


It would be pretty simple to properly run a ground rod & #6 wire into your box, probably $25 or less, and make this building safer. If you don't plug in any 3prong items, yea this is a typical old, old setup. But, for the cheap items needed, sure would be a good simple upgrade.

I'd sure want the house sub-feed fixed up proper, I would not sleep well knowing that trap is waiting to hurt someone in my house.....

The outbuilding is so simple to fix, I'd do that too.

--->Paul


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## sammyd (Mar 11, 2007)

> Sammy, if by "leaving the neutrals disconnected" you mean just hooking the neutrals into the neutral bar in the subpanel, but not connecting them to a neutral wire back to the main panel, then come to my barn sometime and see the lights come on.


I meant this


> do you let the neutral wires for the circuits just dead end in the breaker box


Dead ended is different than terminated on a bar.


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## Nancy_in_GA (Oct 20, 2004)

Sammyd, I owe you, and everyone else, an apology, bigtime. I replaced the tiny 2-breaker box in the barn today and there *WAS* a tap over to the neutral bar from the bundle of grounding wires, which I couldn't see until I tore everything apart. Disconnected this wire and, sure enough, nothing worked. 

So the new 4-breaker box is up and running, but for now, it is set up like the old one. (I really needed at least one more breaker in order to be able to disconnect the fence without also disconnecting the lights or receptacle)

Eventually I will dig up the 330 feet of buried cable from the house (the "PITA") and replace it with 4 wire cable, but will take my chances for now at least until it rains. And I'll install a ground rod there, too, unless someone tells me it will interfere with the fence grounding system.

ps. On the house subpanel, someone privately e-mailed a suggestion. To fish an additional wire alongside the 3 wire cable to act as the missing neutral, snap tie it neatly to the cable (and of course separate the neutral and grounding wires), and add another ground rod. I think I can do this with some patience.

Thanks for the help.

Nancy (feeling really stupid right now)


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## rambler (Jan 20, 2004)

Sounds like you are finding your way through.

========
You keep mentioning 'grounding wires' - are you getting the terminology correct here? The ground wires are always the bare or green ones, really never should be used unless something goes wrong & then they are a real life saver. It would not matter (to the motor or lightbulb hooked up!) if they are connected or not.

Neutral wires are the (Edit, I goofed!!!) WHITE wires that are used as part of the circut, & must be connected or nothing will work.

I fear if you have the terminology wrong, we can hurt you a lot more than help you here. Your circut wouldn't work with the _neutrals_ not connected, but it would work with the _grounds_ not connected. Your description is kinda scary, because it just isn't proper....

=============
You would not need to replace the feed wire to this building with a 4 conductor wire. Code allows you to have 3 wires & a ground rod at the building. No need to go to the expense of replacing 330 feet of buried cable!

=========
The extra wire in the house will work, but I think code doesn't like that very well. I donno. They like things neater than that, not stray wires running around (even if you have it clipped to the feed wire...)..... A single wire would be confusing to the next person working on the whole system, and Code does not like confusion..... This is the one where you really should replace the whole feed cable.....

--->Paul


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## cfabe (Feb 27, 2005)

Code does allow a 3-wire feed with a ground rod at the outbuilding. BUT... it needs to be a 3-wire feed with a full size neutral, not a piece of 2 conductor NM with a ground. You can't use the bare groudn conductor as a current carrying conductor.

It sounds like you're on the right path nancy. I agree with the suggestion to run an additional single neutral wire to the house subpanel and rewire it as a 4-wire feed, keeping the neutrals and grounds seperate back to the main panel. It's not code but given the cost of copper if you're tight on cash and have a long feed to do, it would be better to use a single wire than not do anything at all. 

You might be well advised to surf over to some of the electrical forums:
http://www.electrical-contractor.net/forums/ubbthreads.php
http://forums.mikeholt.com/
These are forums used by professional electricians, they don't allow posting from a layperson, but they have a search feature that you can use to find discussions on your topic. Most of the advice you've gotten here in this thread has been pretty good but there are some errors, you can probably get better advice on the electrical forums.


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## farminghandyman (Mar 4, 2005)

WRONG, WRONG WRONG.



> Neutral wires are the black wires that are used as part of the circuit, & must be connected or nothing will work.


BLACK / RED is a hot wire (and other colored wires can be used in some occasions) , 

WHITE is neutral, 

BARE or GREEN ground/earth.

(Exception: if a different color of wire is used it is to be clearly marked by tape or coloring the wire to the correct COLOR designation for its use, 
Normally, this is only done on main incoming wires, and in some three phase situations, and on some switch legs, there are code rules on how this is done and where it is permissible).


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## morrowsmowers (Jun 14, 2004)

farminghandyman said:


> WRONG, WRONG WRONG.
> 
> 
> 
> ...


That is correct. Your black wires tie into the circuit breakers. The white wires all tie into a common neutral bus bar and the green or bare wires all tie into a common ground bus. Ground and neutral are not the same (but people will tell you they are!). You will see red wires used for positive on 240v lines (black and red are hot) and on switch legs.

I was also told not to add an extra ground rod if I install a sub panel for my shed. I was told that according to national code they want one ground rod at the main panel and all other panels grounded back to that one main panel. That would be your four wire connection -- 2 hot wires, one neutral, and one ground.

Ken in Glassboro, NJ


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## rambler (Jan 20, 2004)

farminghandyman said:


> BLACK / RED is a hot wire (and other colored wires can be used in some occasions) ,
> 
> WHITE is neutral,
> 
> BARE or GREEN ground/earth.



Yup. My mistake, I know it, somehow wrong color came out of my fingertips. Thank you all for the correction. I edited my message above.

--->Paul


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## farminghandyman (Mar 4, 2005)

here is a Mike holt newsletter that has a few graphics and may help,

250.6 Objectionable Current.
http://www.mikeholt.com/newsletters.php?action=display&letterID=458

here is a few more that I would suggest to down load and save,
âTop 101 NEC Rulesâ 

http://www.mikeholt.com/newsletters.php?action=display&letterID=182
http://www.mikeholt.com/newsletters.php?action=display&letterID=205
http://www.mikeholt.com/newsletters.php?action=display&letterID=218
http://www.mikeholt.com/newsletters.php?action=display&letterID=226

link to his news letters one can look them up most have some graphic to illustrate the discussion.
http://www.mikeholt.com/newslettersArchive.php?list=All&back=newslettersCategories.php


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