Why does my main breaker box have a shared ground/neutral?

On Mon, 10 May 2004 03:03:30 -0400, Michael Shaffer put forth the notion that...

It's supposed to. Just make sure you keep them separate at the other end when you run your outlet.

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Checkmate
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Because the current is supposed to flow in the neutral, and the ground is there as a *safety*. I.E. *ALWAYS* at ground, no matter how the current flows. Think of an open neutral somewhere in your house. If the ground, which is hooked to appliance cases, were the same as the neutral, these case would suddenly be at 120V. ...not good.

Ground is your friend (usually). Neutral is there as a return for electrons. They're tied together at your entrance panel to keep the peace. ;-)

Reply to
KR Williams

A neutral is only a return in direct current applications.

Because the current is supposed to flow in the neutral, and the ground is there as a *safety*. I.E. *ALWAYS* at ground, no matter how the current flows. Think of an open neutral somewhere in your house. If the ground, which is hooked to appliance cases, were the same as the neutral, these case would suddenly be at 120V. ...not good.

Ground is your friend (usually). Neutral is there as a return for electrons. They're tied together at your entrance panel to keep the peace. ;-)

-- Keith

Reply to
Brian

| A neutral is only a return in direct current applications.

In Edison 3-wire DC, one line was + and the other line was - so the neutral was technically not always a return. What is really meant is as if each hot line was sending out power, regardless of polarity. And that's the same in DC or AC.

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phil-news-nospam

| I'm thinking of install a 220v 30amp outlet for a welder (small) but my | main service box has the grounds and neutral hooked to the same block.

The neutral is grounded so it is a reference voltage. The neutral used to be the grounding conductor, too. But it didn't serve that purpose very well when unbalanced currents (or worse, fault currents) were present. By having a separate ground wire that is not supposed to take current back to the source, then it can be held an true ground potential, thus avoiding shock when a human touches equipment chassis properly grounded.

Because both wires do go to ground, they have to join somewhere, and that is defined to be the point where power first enters the building. Beyond that, the neutral and grounding wires are not to be connected, or else the unbalanced or fault currents the neutral might be carrying would also be carried by the grounding wire, defeating the purpose of its existance.

What type of plug does your welder unit have? What is the NEMA code for it? Does it have a 6-30P, 10-30P, or 14-30P (with maybe an L suffix)?

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phil-news-nospam

I'm thinking of install a 220v 30amp outlet for a welder (small) but my main service box has the grounds and neutral hooked to the same block. Take a look

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Reply to
Michael Shaffer

Your picture shows main lugs only. Where is the main service disconnect and overcurrent protection? The grounding conductor, grounded conductor, and grounding electrode conductor are suppose to be bonded at the service disconnect. Your panel does not look like a service to me. I have an article on this at:

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Reply to
Gerald Newton

Reply to
Phil Munro

| That's all there is except for the meter.

To totally disconnect all power, how many breakers and/or switches do you have to operate into the off position to get it all off? The NEC code allows for no more than 6.

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phil-news-nospam

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Phil Munro

Use a screwdriver whose shaft is insulated for this purpose. In a pinch, spiral wrap the shaft with electrical tape, with 1/2 overlap so each point has two layers of tape. Just leave the last 1/4 to 1/2 inch of the tip exposed.

Some boxes, with a lot of stray bare conductors not neatly tucked in can be very scary places. Especially when you try to push them aside to reach a breaker :-)

daestrom

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daestrom

Reply to
Michael Shaffer

It is very unusual to have ready access to the mains when they are only protected by the primary fuse at the service transformer. That seems to be you situation. Before working on this panel hot I would carefully perform a hazard analysis to determine the risks that you may be taking. The fault current could be extremely high and you could be placing yourself in harms way by working this panel hot. I am an electrician with over 40 years experience and I shy away from working on any hot circuits on the supply side of a service disconnect. These hot circuits are like working with nitroglycerine. I would contact the utility company and see if they can pull the meter to de-energize the panel before working on it. I would also ask for a courtesy inspection by any authority having jurisdiction including the utility company. Most utility companies seal any disconnect, box, meter, or panel that allows direct access to the supply side energized circuits.

Reply to
Gerald Newton

|> Michael Shaffer wrote: |>

|> > Ok, I just looked and I guess I thought there were more. There are 5 |> > breakers, one emtpy slot. |> >

|> > snipped-for-privacy@ipal.net wrote: |> >

|> >> On Mon, 10 May 2004 23:06:13 -0400 Michael Shaffer |> >> wrote: |> >>

|> >> | That's all there is except for the meter. |> >>

|> >> To totally disconnect all power, how many breakers and/or switches do |> >> you have to operate into the off position to get it all off? The NEC |> >> code allows for no more than 6. |> >>

| It is very unusual to have ready access to the mains when they are only | protected by the primary fuse at the service transformer. That seems to be | you situation. | Before working on this panel hot I would carefully perform a hazard analysis | to determine the risks that you may be taking. The fault current could be | extremely high and you could be placing yourself in harms way by working | this panel hot. I am an electrician with over 40 years experience and I shy | away from working on any hot circuits on the supply side of a service | disconnect. These hot circuits are like working with nitroglycerine. | I would contact the utility company and see if they can pull the meter to | de-energize the panel before working on it. I would also ask for a courtesy | inspection by any authority having jurisdiction including the utility | company. Most utility companies seal any disconnect, box, meter, or panel | that allows direct access to the supply side energized circuits.

IANAE, but if this were me, I'd definitely NOT work on a panel hot, and especially NOT the one I see in that picture. I especially don't like the placement of the neutral and ground bars relative to the main lugs.

This is most definitely a case to have the power company come out and pull the meter for the day, at the very least.

IMHO, you should hold off on adding a circuit and take a look at doing a complete changeout to a new panel with more space and a real main breaker. Or at least add a separate enclosure for a main breaker by itself and run the service through that first.

Do you have children living in the house?

Also, you need to consider the added load this is putting on the service entrance. Since there is no main breaker, you have to add up all the lower section submains, plus the breakers above them (which should total no more than 6), and make sure the service wiring can handle that amperage. What I see doesn't look like it will do more than 100 amps, but there could easily be over 100 amps of unchecked load with an added 2 pole breaker.

What is that disconnect box on the left?

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phil-news-nospam

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Michael Shaffer

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Michael Shaffer

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Michael Shaffer

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Michael Shaffer

Gerald, don't you remember when it was legal to run unfused service entrance conductors for long distances without a main overcurrent protection? You still could not have more than 6 main disconnects at the panelboard. Most of those panelboards were "split-buss" panels, where one of the mains was used to feed the lighting and receptacles. Now, of course, you cannot run the service entrance more than about 5 feet or less without a main breaker. Usually just on the opposite wall back-to-back with the meter box. Make sense? Later... Blue Crown

Reply to
Blue Crown

The neutral and ground are usually tied together in the CB panel or fuse panel of a residence. A #4 copper wire should go from the neutral bar to a

8 foot ground stake that has been pounded into the ground someplace.

Your best bet would be to install a 30 amp single trip/dual circuit breaker (or 2 circuit breakers with a common trip) and feed your welder off of it.

--jj

Reply to
Cougercat

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