coloradotrout wrote:
On Jan 7, 11:29 am, coloradotrout wrote:
On Jan 7, 10:46 am, bud-- wrote:
coloradotrout wrote:
On Jan 5, 12:26 pm, bud-- wrote:
coloradotrout wrote:
Any receptacle that gave a "funny" indication had a bad ground. It could
be a circuit or the whole panel.
Not only are some outlets not grounded, if a failure at one outlet makes
that ground "hot" many other outlet grounds are "hot". Real bad condition.
To test the ground, connect a light bulb from hot to ground. If the bulb
does not light the ground is open. The bulb should light at full brightness.
Makes be wonder if
the box has a good earth ground or not.
It is not an earth ground problem.
The "ground" wires return to the service. At that point there is a
connection between the "grounds" and the incoming service neutral. (This
is typically a screw from the neutral bus to the enclosure.) On a fault,
like yours, the ground wires go back to the service panel, connect to
the service neutral, and go to the power transformer. That gives a high
current path that will trip a circuit breaker. This is a main function
of "ground" wires, and will happen without an earth connection.
Connection of "ground" (and neutral) wires to the earth keeps a low
potential with respect to the earth. If the "ground wire"-neutral bond
at the service is missing, there will be some return through the
earthing electrode, through the earth, to the earthing electrode at the
transformer. If you had a quite good resistance to earth of 10 ohms,
your fault (120V to earth) would produce a current of 12 amps - not
likely to trip a 15A breaker - there would be a significant delay even
if the breaker was fully loaded.
Bud,
So I should look in my panel and see that the neutral is grounded to
the box?
I thought I recall seeing 3 large wires coming into the box - hot,
hot, and neutral. The box itself then has a ground bar and two
neutral bars ( I think). I do not recall seeing any neutral to box
connection.
Suspect the OP does not understand wiring sufficiently and/or has made
basic error in wiring.
Also is this being wired from the main panel of the house or pony
panel? There is mention of "three wires coming into the panel"! And no
connection between neutral and ground; so it's a sub panel?
Also we are talking 230 volt outlets; not what are sometimes called
Edison outlets or here sometimes called 'split outlets'?????
Split outlets (allow you to plug in more load). Namely when the
connection between the upper and lower parts of a duplex is
deliberately broken by removing that link on the hot side of the
duplex and a common neutral is used, the upper half uses one 115 volt
leg (say red) and the other half uses the other leg (say black). Thus
effectively two separate outlets on the same 230 volt common neutral
circuit breaker.
And who is to say the pony (if indeed it is that) is wired correctly?
Very confusing; but sounds like it would take less than an hour to
sort out!-
I'm not wiring expert, but the panel was already in-place. From the
pole there is a 100A breaker that feeds this panel.
I added the circuits noted - 2 x 220V and 1 x 110V. For the 110v, I
wired white to the neutral bar (where the other 110v white wires were
connected, the bare ground to the bare ground bar, and the black to
the breaker. For the 220v circuits, bare ground to bare ground bar,
white to one screw on the breaker, and black to the other screw.
These are square D panel/breakers. Nothing fancy, all basic
components.
Note my last post -- the detected problems are resolved, but the
concern is I still have an open ground somewhere, else the previous
problem would have trippped a breaker.
If there is an open ground you really need to fix it. If receptacles on
multiple circuits had "funny indications" I would suspect missing
ground-neutral connection at the panel if it is a service panel. Else it
might also be a defective ground on that circuit If it is a sub-panel
maybe a defective ground in the feed. If it is a sub-panel in a
different building, how is it fed - only 3 overhead wires? I gave you a
ground test using a light bulb.
If it is a service panel
- the utility supply will come in through a meter to the panel
- there will be no disconnect between the utility connection and the
main breaker in the panel.
If it is a service panel and wired to the National Electrical Code it
will have
- a heavy wire connected from neutral/ground bus to grounding
electrode(s); in older installations the water service pipe; in newer
installations an additional electrode, commonly a ground rod.
- and a jumper between the neutral bus and the enclosure.
If it is not a service panel, but is fed from a different building there
are options.
If there is a jumper between the neutral bus and enclosure, as I wrote
in a different post, it is commonly a screw from the neutral bus to the
enclosure. The SquareD panels I have seen it is an ordinary looking
round or pan head screw about 10-32. Sometimes they are colored green.
If it is not there, there should be an empty hole in the neutral bus.
The bonding screw is not obvious at all.
If this is a separate building, like a garage, it probably needs to be
wired similar to a service. (I have seen electricians argue about the
relevant code sections.) You have not provided enough information
You may want to call an electrician.
For your 220V circuits, if you are using Romex or other cable, the
"white" wire should have been covered with tape to make it a different
color than white or green. It should have been re-colored wherever the
wire appears. (If using fished wires, white shouldn't have been used.)
The service comes down to the pole into a box. That box has a 100A
breaker that runs to the shop, and a 200A breaker that runs to the
house. The pole to shop is about 200 yards and there are 3 large
wires.
The meter and service are at the pole. The house and shop are subpanels.
The shop and house panels could have hot-hot-neutral-ground feeds and be
wired with a separate ground bar and no N-G bond. Grounding electrode(s)
required (also required in the other method).
Your description is hot-hot-neutral feed. The shop and house panels are
wired the same as a service panel. Neutral-ground bond required (neutral
and ground bars are effectively the same).
[This method is not allowed in the 2008 NEC for new installations. Seems
like what you have is common and safe.]
With a separate ground bar I suspect your panel doesn't have a
neutral-ground bond. If missing it could be a mistake or a local wiring
practice or inspection authority quirk. IMHO it is not safe. The NEC
does not allow the earth to be used as a return. That is because the
earth does not provide an effective return. The need for a metal (not
earth) path for ground fault current back to the transformer is not
understood as well as it should be.


Resorting to my old analog multitester (bec. the battery in the cheap
digital one is dead...)
breaker bar L to neu bar - 120v
breaker bar R to neu bar - 120v
breaker bar L to breaker bar R - 240v
breaker bar L to grd - 120v
breaker bar R to grd - 120v
neu bar to grd - 1v (a trace of voltage, but not 0)
resistance between grd and neu - 20 ohms (that's 2-0, and not K, etc,
I was on the meter 1x setting)- H
..
The voltage of interest is N-G.
If there is voltage from N-G you can't measure the resistance. 20 ohms
could be a reasonable measurement if the shop subpanel has no N-G bond
and the path is through the earth.
..
Bud --

I did some reading tonight in some 'code' book at Lowes. I now see
what you mean by neu-to-grn "bond". There is suppose to be this
"bond" in the service panel, and then any sub panels should be fed by
4 wires - hot1, hot2, neutral, ground.
..
That is true for a subpanel in the same building.

It is one way to wire subpanels in a *different* building.
..

But my shop panel is fed by 3 wires - hot1, hot2, neutral. There is
only an earth ground in the panel.
..
That was a second way of powering a *different* building. But the NEC
then requires a N-G bonding jumper. Without the jumper there is no metal
path back to the transformer, and a short-to-ground will not reliably
cause a breaker to trip (and can make the "grounds" hot).
..
I guess I should go pull the cover off the panel on the pole (which
feeds the shop on a 100A breaker and the house on a 200A breaker).

What should the pole panel look like?
..
Who cares.
..
What should my shop panel look like? (given it has 3 wires from pole
panel)?
..
You still don't know where the grounding problem is. From what I
remember it could possibly be one circuit (but probably not).

Connect a light bulb, 100W or larger would be nice, from a hot to
ground. Is the light fully bright? What is the voltage between the
neutral and ground bus? Note all the grounds in the building, including
the panel, may be "hot" when you do this.
If you actually have 20 ohms N-G, a100W light bulb might give you about
15V from N-G. I would expect well under a volt if there is a N-G bond.


As I said a couple times, the N-G bond is often a screw that looks like
it could just be a mounting screw for the neutral bus. Recent ones are
probably green. If not installed there will be an empty hole in the
neutral bus.
..
What should my house panel look like? ( I need to look at it also)
..
If the shop panel does not have the N-G bond I would certainly check the
house (or check it anyway).

You may want to call an electrician.

(There is a minute possibility local practice is to not add the N-G
bond. That would be very unwise.)

--
bud--