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winchman
07-07-2010, 05:10 AM
My friend's pump house is about 150 feet from his house. There's a 10-2 w/G cable buried alongside the water line. The pump is 220v, and there's an outlet for 110v. It was all put in when the house was built, or possibly by a previous owner.

Obviously, the side of the outlet that should be connected to neutral is connected to the ground, as is the ground of the receptacle. The ground wire of the cable is connected to the ground in the main panel in the house. Of course, the neutral in the panel is also connected to ground.

The correct way to fix this situation would be running a new 10-3 w/G cable between the main panel in the house and the pump house. The location of the water line and cable is not known, and that's a lot of expensive wire and a lot of work involved.

He's thinking about installing a ground rod at the pump house, continuing to use the cable ground wire as the neutral for the 110v receptacle, and using the new rod for the ground. Obviously this will work, but will it really be any better? Should the new ground rod and the neutral/ground wire in the cable be connected?

It's my understanding that the reason for prohibiting the use of the ground wire as the neutral is to prevent having other grounded points in the circuit become hot if something happens to the neutral closer to the panel. That cannot happen in this situation, since the wire runs straight to the panel ground with no other connections.

garagemark
07-07-2010, 06:46 AM
I doubt if anyone will tell you that it's right to do what you describe- it isn't. However, down on the farm and in reality, many many worse installations have been realized, with favorable (so far) results. I would consider a two pole ground fault circuit breaker instead of a rod. A bit pricey but effective.

GKman
07-07-2010, 07:34 AM
I haven't seen an NEC codebook for a while but the behavior of electricty hasn't changed so I'll offer this. NEC used to require that if one building feed another that the new building starts over with it's own grounding system. Sounds similar to what you have. The neutral conductor for the 120 v circuit wouldn't have it's own insulation, only the cable jacket, but it should be at ground potential from the neutral-ground bond in the service that feeds it. The 120 v recepticle should be a GFI. I don't see how there would be iny improvement in safety or functionality by running an additional grounding conductor 150'. A well casing is the gold standard for g ground. The building supplying it may have a plastic water supply, no rebar and a 6' rusted ground rod in soil too dry to carry any fault current to speak of.

The floor is open for discussion.

winchman
07-07-2010, 08:03 AM
He is planning on replacing the 110v receptacle with a GFI receptacle. That fact didn't seem pertinent to the discussion, so I left it out.

It pipe to the house is plastic, as is the well casing and the drop pipe. That's one reason he's thinking a ground rod is necessary at the pump house.

J Tiers
07-07-2010, 08:22 AM
The "neutral" is called teh "grounded conductor", because it is in fact grounded, back at the service. That is the ONLY place it is grounded*.

The neutral is a "current carrying conductor".

The "ground wire" (USA) is the "equipment grounding conductor" (EGC). It links all the metal parts of the system together so that they are at the same voltage. It should NEVER carry anything but fault current. THE EGC IS NOT A CURRENT CARRYING CONDUCTOR.

If the EGC DOES carry current, a voltage drop will be developed, and some parts of the grounding (earthing) system will be at a different voltage than others.

There is another thing..... in case of a fault shorting a hot wire to ground (earth), the EGC provides a low resistance path that will cause the fuse or circuit breaker to open on over-current.

Now, in this case, there are several problems.

1) The EGC doesn't exist. Therefore, there is a HIGH RESISTANCE ground path (50 metres of dirt), and a short to "dirt ground" may NOT open the circuit protector.

2) The local ground can develop a substantial voltage vs the system ground rod, as in case 1, and this could be hazardous, depending on what may or may not be touched, either in operation, or servicing.


I'd have to look up the specific type case just as a check. But the rule is that remote grounds should be made to have the same potential as the rest of the ground system, so that the voltage of "ground" is the same everywhere.

That would suggest running an EGC and tying it to a local ground rod.

The NEUTRAL can only be bonded to ground one place, but no such rule attaches to the EGC.

*
In other places, "ground" is called "earth". "Ground" is probably the more general term, as there is usually no "earth" in an airplane, but a wire may be "grounded" to the structure.

The entire aircraft may then be "earthed" during fueling while not in the air........

wierdscience
07-07-2010, 08:31 AM
That's a common installation here,10/2 to the pump shed and the 110 split off and returned through the neutral.It's also a common setup in water heater and furnace closets.

The only time a ground rod is added is when a sub-panel is added.Oh I would add also the 110v is usually only for a lightbulb.

Richard-TX
07-07-2010, 08:48 AM
A GFCI will not work correctly if there is no separate ground.

What you have described is likely in the top 20 of code violations.

A single light bulb may be OK in this case assuming plastic junction boxes.

Abner
07-07-2010, 09:53 AM
You are deciding between a 3 wire and a 4 wire system. The code was changed when my house was built to 4 wire( 2 hot, 1 neutral, 1 ground, neutrals and grounds separated in the electrical panel). They have since gone back to 3 wire( 2 hot, 1 neutral/ground).
At the time my well was installed if you were over 10' from the meter base/main disconnects then you had to have a separate ground rod.

You should follow code for a variety of reasons. Having said that, I would think a separate ground rod grounding the pump house panel would be required and safer.
Keep in mind that code is the minimum required. Floor deflection of 1/360 will still rattle china in a hutch with a heavy stride and will still meet code.

garagemark
07-07-2010, 10:06 AM
A GFCI will indeed work without a separate ground. In fact it does not look at the ground at all. Only the imbalance between the hot and the neutral. However, a two pole will not work in this case, it is designed for both hot legs to be balanced. A 120 volt load on just one leg will create an imbalance and will trip a two pole GFCI.

Drive the ground rod if you wish.

RancherBill
07-07-2010, 10:21 AM
Put in a new cable and do it right.

It was a 220 circuit and you are trying to change it into 110/220, it reminds me of those guys who used to take a station wagon and turn it into a pickup. It sorta almost worked, most of the time.

Tell your neighbor to do it right - kludges last for ever and they are just that kludges. There are many future scenarios and the NEC is a safe way to do it.

lakeside53
07-07-2010, 11:10 AM
If the only reason you are going though this is to put a light bulb in the pump house, use a 220v light bulb bulb and forget runing new cable, ground rods etc...

If you need a receptacle for a heat tape or general use, you'll need to run new cable and a ground rod. The "g" portion of your 10/2 cable does not have the same insulation as the current carrying conductors. I doubt its legal to use that as a neutral.

I converted an old pump house last weekend to provide power to a garden and Air streamer. 25 years ago they had run 3 #8 aluminum direct bury conductors, but there was no ground at the pump house, and it was complete with receptacles, power cords lying in water .. rusted metal boxes... great. I rewired the internals, a ground rod and sub panel, and three GFCI breakers (I was wasn't paying :))

Carld
07-07-2010, 12:33 PM
deleted message.

Black_Moons
07-07-2010, 12:50 PM
This sounds like an awful idea.

Anything happens to that ground, And everything 'grounded' in the pump house becomes live due to that load.. Current will start travling down your water pipes (in the water) if theres grounded pipes elsewhere.

Ground is NEVER to be used for a load! Because that makes things MORE unsafe, ground was designed to make things SAFER, and is tied to the metal housing of EVERYTHING electrical.

Now, if you want REAL solutions:

Blah blah, replace wire, Durrr. Expensive, labour, yadayada. Don't like it? ok fine.
Buy a 240v->120v transformer, Bind one output to ground so one side becomes a non floating 'neutral'
Whats the diff you ask? the diff is ground isent being used to carry current anymore. If it fails its just a floating ground, Not one thats tied to 120v AC via a low resistance load.
They even sell them as US/UK 'converter' transformers. Expect $50~150 depending on wattage required, but I think this is the cheapest and safest and least labour intensive solution.

Just running lights? Buy two 120v incandesent (I don't think CCFL's will enjoy this) and run em in series (SAME WATTAGE VITIALY IMPORTANT)

Running something else? See if you can't get one on ebay shiped from the UK :P
Basicly everything 50hz 240v except wall clocks will run on 60hz 240v.

Andrew_D
07-07-2010, 01:05 PM
Could it be made to work? Sure, lots of folks here have given suggestions as to how they might attempt it.

Should you do it? Well now, that's iffy. What are you going to do if there is ever a fire in the pumphouse? Whether the electrical was the cause or not, your insurance investigator is going to see improper electrical and the stinky stuff will hit the fan.

Do it right and then you will know you are covered.

Andrew

davidh
07-07-2010, 01:31 PM
i just can't wrap my headaround my 220V, 2 wire submersible water pump. two hot leads, no return leg, ground wire, etc etc. . . . works fine but why should it ?

jep24601
07-07-2010, 03:12 PM
i just can't wrap my headaround my 220V, 2 wire submersible water pump. two hot leads, no return leg, ground wire, etc etc. . . . works fine but why should it ?
The hot wires are each 110v but 180 degrees out of phase from each other giving 220v across them whereas each would only read 110v to ground or neutral. Because they are 180 degrees out of phase they have the opposite potential from each other and thus the current flows back and forth between them with no need for a ground or neutral.

Boucher
07-07-2010, 03:48 PM
I retired from the water well business in 2003 and have not kept up with the recent changes. The Codes for well pumps started changing about 1995.
Basically it became manditory when the well was serviced that a ground wire be run all the way to the submersible pump. That necessitated new four wire pump cable be installed. Copper prices were much lower back then but it was still a significant cost. The changes also requirred a driven ground be added at certain points. Most voltage spikes result from lightning strikes on the ground of the electrical service system and I originally thought that the code changes were the Electric companies way of improving their ground at the individuals expense. Over time I came to view the changes as beneficial.

Your friend should bite the bullet and bring his system up to current standards. There are some things that I know have happened that I cannot understand or explain like stock being shocked at a water trough and people being shocked in the shower. These ceased to occur when the ground code changes were implemented.

winchman
07-07-2010, 04:11 PM
As I said in the first post, I know the correct way to fix it. I was having some trouble seeing the potential problems associated with the easy fix.

With the correct wiring, a break in any of the wiring will only mean that whatever it's supplying won't work. That's inconvenient, but not unsafe.

With the easy fix, it's possible that a wiring problem could create an unsafe and potentially lethal situation, as Black Moons and others have pointed out.

Thanks, guys, I understand it now.

Don Young
07-07-2010, 09:52 PM
Possibly the cheapest and best solution, IMHO, would be to keep the existing ground wire and install a small 240-120V transformer to feed the 120V circuit. An uninsulated conductor would never be correct for a neutral, whether or not it was also used for a ground.

I do not know the NEC grounding requirements for this case but you can never go wrong following the codes and accepted good practice. To do otherwise is to invite potential hazards. Hazards involving electricity and water tend to be serious. A lot of the fires and electrocutions happen with systems that "work fine".

J Tiers
07-07-2010, 10:19 PM
I actually read through the code for the type case here...

Basically it isn't a special case...... it's just a branch circuit.

You don't have a neutral, and you need one for the outlet. So that ground wire looks good. But it isn't a neutral, and if it IS a neutral it can't be a ground also.

But you need the ground.

Without the outlet, it is OK, you have a ground wire, and can do it per code. WITH the outlet, you got problems.

Can you lose the outlet? Lights can be wired in.

A transformer would be a "separately derived system", and the outlet could be connected to the secondary, with the "local neutral" bonded to the well casing and a ground rod to provide teh ground for the local EGC. At an electrical surplus joint, you can find "four-way" 120/240 to 120/240 transformers for $25 or so. Outdoor ones. That gets you the ground back as a ground, and you can connect it per code.

Otherwise, if you need the outlet, you are probably stuck.

There IS a clause that covers outbuildings that have a single branch circuit going to them..... but this case is sufficiently goofy, with the well, water, etc, that the inspector may not allow you to claim that, and it only "sort-of" applies.

You CANNOT use the neutral as a ground on the load side of the service box. And you cannot use the ground as a neutral, because it is a bare wire ground, presumably, and if not, is a green wire.

So you pretty much are looking at replacing the cable to make it a safe install that satisfies the provisions of NFPA 70 (the NEC).

darryl
07-07-2010, 11:19 PM
It's pretty simple really. You have 220 there for the pump, and without a neutral you don't have a return to give you a 110 circuit. So- what do you need 110 there for, a light? Use a 220 v light and switch, or put two bulbs in series and use a switch rated for 220. I could be wrong, but I thing the standard light switches are rated up to 280v or so- might want to check on that. The single 220v bulb would be the best choice.

If you wanted to draw any significant current at 110 volts, you'd be adding that current to whatever the pump wanted when it came on. That could easily overload the breaker on that phase, and then the pump would not run. Say you have an electric lawnmower plugged in, or maybe even a heater in the wellhouse- not unheard of in cold weather- poof, no runny the pump. Only way for significant power out there at 110v (more than a lightbulb would draw) is to run a second wire.

Adding a transformer to drop the voltage to 110 for a light means adding another potential future problem, though it would work. Using the existing ground wire for a neutral return does work, but it should not be used that way. Given the tactics used by insurance companies these days, that's all they would need to cancel a claim if it could be even remotely tied to improper wiring.

If it's a light that needs powering, do what it takes to install a 220v light and be done with it.

rdfeil
07-08-2010, 01:22 AM
All of the above "legal" suggestions are good and acceptable. The first question that needs an answer is... What is the 120 volt circuit for? If it is for a light, just use a 220 volt lamp and switch. If it is for an actual 120 volt only purpose, power tools, battery charger, convenient place to plug in an extension cord etc... Then you need a safe way to get 120 volts. The only legal ways to do this is to either run a new wire with 3 insulated conductors AND a ground or use a transformer as mentioned above. With the transformer you create a "separately derived system" as J Tiers stated and the local ground is created with a local ground rod. Another thing to remember is that the power in the pump house is protected only with the circuit breaker for the pump. If it was done properly the 10/2 G will be feed with a 30 amp 2 pole breaker. This is not a legal way to feed an outlet in any case. The outlet should be fused / breakered at 15 or 20 amps depending on the outlet and wire feeding it. If it were mine I would install a small breaker panel in the pump house and use it to feed the pump and a transformer. Then the transformer could feed another small panel to feed the outlet and light if needed. The only problem with this is that you are still limited to less than 30 amps total on the 220 volt feeder. This might not be a problem, but it is something to remember.

Robin

Paul Alciatore
07-08-2010, 02:10 AM
It has all been said. The only thing that dictates the use of a neutral is the 115V outlet. You can simply remove it and you are OK with two hots and a ground. Or add a transformer or if it is for lights, use a 230V lamp (or two identical 115V lamps in series). All should be acceptable under the code.

Another thought for lighting, would be to go low Voltage lights.

Adding a ground rod is an "iffy" thing. I have measured the resistance of such locally driven rods and it can vary quite a bit. If you have a good water table and it is consistent, the resistance can be quite low. On the other hand, if the ground is dry the resistance can be very high and the ground rod is almost useless. There is no guarantee that it will do it's job.

If you must have both 115 and 230 Volts, then you need the neutral and that means a four wire system.

J Tiers
07-08-2010, 08:26 AM
Adding a ground rod is an "iffy" thing. I have measured the resistance of such locally driven rods and it can vary quite a bit. If you have a good water table and it is consistent, the resistance can be quite low. On the other hand, if the ground is dry the resistance can be very high and the ground rod is almost useless. There is no guarantee that it will do it's job.


I agree on "iffy" ground rods....

BUT.... 2 things......

1) the ground in the wire, which exists, is supposed to be connected to any local rods, so that the return ground current has a low resistance path regardless.*

2) per the code, ground rods are supposed to be lower than 25 ohms resistance in ground. BUT, in the infinite wisdom of teh code writers, it it is NOT, i.e. you have dead dry soil, you only need to pound in one more, and the code considers you good and legal.


#2 leads to #1, as night follows day.


And, since tehre already IS a ground wire, the branch circuit is not ungrounded, and so you don't have an ungrounded system, and can't wiggle out there by putting in a local one only.

Yes, the 30A circuit which MIGHT be presumed from 10 ga wire is a problem if true. The 10 GA might also be installed merely on account of the distance and voltage drop..... There is at least 50 metres of that, PLUS whatever is in the well leading to the pump, so it isn't a slam-dunk that there is a 20A breaker.

but if there is, that knocks out the outlet, yes..... at least if direct-connected

*
The ground is supposed to be able to open the breaker in case of a fault..... needs low resistance.

jep24601
07-08-2010, 09:35 AM
[QUOTE=Richard-TX]A GFCI will not work correctly if there is no separate ground.QUOTE]

A GFCI trips when it detects a difference between the hot and neutral current.
It does not need a ground in the system to do this.
In really old homes which do not have ground wires you can install GFCI's for safety. Not Code? - codes are not retro-active.

Paul Alciatore
07-08-2010, 12:41 PM
[QUOTE=Richard-TX]A GFCI will not work correctly if there is no separate ground.QUOTE]

A GFCI trips when it detects a difference between the hot and neutral current.
It does not need a ground in the system to do this.
In really old homes which do not have ground wires you can install GFCI's for safety. Not Code? - codes are not retro-active.

Actually the ground is essential and can not be replaced with a GFCI device. The ground is to protect you from shock AND to trip the breaker from high current situations (shorts) which could result in excessive heat and possibly a fire. It also protects from shock when the outer case is conductive and grounded. There are too many different fault scenarios but the code has evolved to cover most, if not all of them.

The ground is the first and most basic protection and it MUST be present. Then, a GFCI is added if it is needed. The GFCI is designed to trip the breaker if just a low level of current is detected as missing in the neutral or return path. It is assumed that this missing current is passing through your body.

On the low resistance thing for a ground rod, consider: a 30 Amp breaker needs more than 30 Amps to trip. I=E/R or R=E/I. 115V / 30A = 3.83 Ohms. So a 25 Ohm ground rod will NOT provide enough current to trip a 30 Amp breaker or even enough to trip a 20 or 15 Amp one. Code or no code, it won't work. A 1 Ohm ground is a good one in my opinion. That would blow up to a 100 Amp breaker. It is hard to get that but it can be done.

ulav8r
07-08-2010, 12:42 PM
Instead of running a 4 wire cable, why not run a single wire to serve as the neutral? Leave the ground wire as a ground and connect it to a ground rod at the well.

jep24601
07-08-2010, 05:22 PM
[QUOTE=jep24601]The ground is the first and most basic protection and it MUST be present.
- but in many old homes it isn't.

lakeside53
07-08-2010, 09:04 PM
.. and a GFCI works fine without a ground (and is better then the alternative of a non-grounded outlet) in those old homes... like my MIL's 1906 houre in MT - about 70% of the oiutllets are 2-wire, and still tie to knob & tube.

And yes, a ground is always very good idea!

lakeside53
07-08-2010, 09:07 PM
Instead of running a 4 wire cable, why not run a single wire to serve as the neutral? Leave the ground wire as a ground and connect it to a ground rod at the well.


All the wires either need to be in the same "conduit" - the casing of the 10-2 UF, or individividual direct burial type.

If you're going to dig a new trench at the code depth, new wires are the easy part.

J Tiers
07-08-2010, 09:58 PM
[QUOTE=jep24601]

Actually the ground is essential and can not be replaced with a GFCI device.


Code allows using a GFCI, which has a 3 wire outlet, on a 2 wire extension, i.e. on wiring that does not, and never has had, a ground.



On the low resistance thing for a ground rod, consider: a 30 Amp breaker needs more than 30 Amps to trip. I=E/R or R=E/I. 115V / 30A = 3.83 Ohms. So a 25 Ohm ground rod will NOT provide enough current to trip a 30 Amp breaker or even enough to trip a 20 or 15 Amp one. Code or no code, it won't work. A 1 Ohm ground is a good one in my opinion. That would blow up to a 100 Amp breaker. It is hard to get that but it can be done.

In lots of soils it cannot be done in any way whatsoever.

The code allows 2 ground rods, and that is IT. End of discussion. No added argument is required.

BUT, luckily, the Code also PROHIBITS a situation where the earth connection between ground rods is depended upon to open the circuit protector.

This is all reasonable......

The REASON for the grounding rod is NOT TO POP THE BREAKER.

The REASON FOR THE GROUNDING ROD is to bring the local "earth" to the same potential as the neutral and equipment grounding conductor.

it is PURELY to ensure that there is no potential between the EGC and the "earth", as that would totally defeat the purpose of the EGC.

if the local earth is so high resistance that it makes a lousy "ground", then the provision of dozens of rods will not improve the local earth-to-EGC potential.

ONLY IN THE CASE of a substation, with tens or hundreds of thousands of amperes fault current possible, is there a real reason for a "ground grid" or "ground mesh" to reduce that potential.