Open-ground hazard

[hedgehopper]

My AC Line Meter indicates "Open Ground." What are the dangers associated with this condition?

Note added: My system is 30 amp and connected to shore power. Shore power is grounded. The AC Line Meter is plugged into a newly added 120v outlet. The indication is "Open Ground" not "Open Neutral."

[myredracer]

OP needs to provide a bit more info., but to summarize the potential risks of an open ground in no particular order:

- death
- mild to painful shock
- fire
- damage to electronics

[hedgehopper]

wa8yxm wrote:
EXCEPTION: If the outlet is GFCI protected.. The ground may be open on purpose as the GFCI will provide protection.

Pls say more. I think the new outlet is on the same circuit with an outlet with GFCI protection.

[time2roll]

If the existing outlets test normal and your newly added outlet has no ground.... FIX THE GROUND CONNECTION on the new outlet.

The hazard is electrocution during a fault.

[wa8yxm]

Ah Open Ground.. Ok, The safety ground is there for your safety.. Now. understand I am typing from EXPERIENCE.. Painful Experience.

Imagine you are holding a metal cased tool (Skill hand grinder) and there is an internal short. Hot to case (There was) Now the case is HOT.

Mains power is grounded, the neutral is bonded to ground at the pole and again at the service entrance so the Ground offers a return path.

And YOU are part of that path (I broke a few grinding points with that thing and finally went out and bought a Dremel of my own (It belonged to my boss)

Now I just suffered some pain.. But if I'd had that in the other hand....
The human body is ALMOST but not quite symeterical (Two halves mirrored)

Example you have a right hand and a left hand

But the HEART is a bit off center (To the left) Had I had that tool in my LEFT hand (I can use either hand) the current path would have been right THROUGH my heart and I might well NOT be typing this today.

And that folks. is the danger of an open ground...


EXCEPTION: If the outlet is GFCI protected.. The ground may be open on purpose as the GFCI will provide protection.

[ktmrfs]

MEXICOWANDERER wrote:
A Little Test

3-wires

L1 load 10 amperes
L2 load 10 amperes
L0 load (?) amperes

SURPRISE

if L0 is the neutral, and L1 and L2 are 120V legs of 240 and the load is resistive L0=0 amps L2 and L1 out of phase 180 degrees and cancel.

when L1 is +10A, L2 is -10A

Need to use vector not scalar math.

[MEXICOWANDERER]

A Little Test

3-wires

L1 load 10 amperes
L2 load 10 amperes
L0 load (?) amperes

SURPRISE

[hedgehopper]

ktmrfs wrote:

MrWizard wrote:
The poster has not come back to say how he is plugged in
Portable generator or shore
I'll guess and say portable, this is the first time he every saw this

agreed. or he is at a campground with a worn out or defective stand at his campsite. My EMS has caught a bad campsite plug/outlet a few times with intermittent or open ground. One case was intermittent. I was plugged in for several hours before the EMS said open ground.

See note added to my original post.

[ktmrfs]

MrWizard wrote:
The poster has not come back to say how he is plugged in
Portable generator or shore
I'll guess and say portable, this is the first time he every saw this

agreed. or he is at a campground with a worn out or defective stand at his campsite. My EMS has caught a bad campsite plug/outlet a few times with intermittent or open ground. One case was intermittent. I was plugged in for several hours before the EMS said open ground.

[MrWizard]

The poster has not come back to say how he is plugged in
Portable generator or shore
I'll guess and say portable, this is the first time he every saw this

[ktmrfs]

MEXICOWANDERER wrote:
Off Topic but relevant nevertheless

"Why is the neutral wire in a 240 circuit the same gauge as both phases (hot wires). Shouldn't the neutral wire be much larger to carry double the current?"

No.

Current in an AC wire "only flows half the time"

If that current can be "filled up" then the wire will be "full".

The 2nd phase wire wills the neutral wire up with a mirror image filling the sine wave gaps.

Three wire to two wire adapter plug test...

Those little plastic adapter blocks that will allow a grounded three wire plug to connect to a two wire outlet is a great diagnostic tool.

You'll need a non contact AC voltage tester for this...

Unplug ANY metal cased appliance then plug it into the adapter then plug the adapter into a wall socket.

Wave the ac detector over the metal of the appliance. If it sounds off there is a fault inside the appliance.

This is a rare occasion where I will disagree with Mex.

current usually flows all the time in an ac circuit when a load is connected, not just for 1/2 cycle. 120V RMS Voltage goes from about +177 v to -177V each cycle as a sine wave. current likewise goes from positive to negative as a sine wave, not necessarily in phase with the voltage depending on what the load is. resistive is in phase, reactive (inductive or capacitive) is out of phase by some degree with the voltage. Now an exception to sinusoidal continual current flow is switching power supplies, even stranger with non sinusoidal and often non continous current flow.

now in a 120/240 circuit you have two 120v legs relative to the neutral, but they are 180 degrees out of phase. so when one leg goes positive, the other leg is going negative. so when you are connected to the 120V legs if the same current is drawn by both legs, there is no current flowing in the neutral the current from each leg cancels with a resistive load. again the exception being non resisitve loads, but even then it will be close to cancelling. if one leg is drawing rated current, the other no current, then the neutral has rated current flowing in it. anything in between has less current flowing in the neutral than either leg.

If you are connected across the hot side of two 120V legs, you have 240V and when a 240 load is connected all the current flows between the two legs and none through the neutral.

In older 240 V wiring, often the neutral was a smaller guage than either hot leg. the reasoning was the main load was across both legs, and only a minor load was across one leg. Like a dryer, the heating element across both legs, and only the timer across a 120V leg, drawing much less current.

[SoundGuy]

hedgehopper wrote:
My AC Line Meter indicates "Open Ground." What are the dangers associated with this condition?

Potentially a Hot Skin Condition that can kill. :E

[MEXICOWANDERER]

Off Topic but relevant nevertheless

"Why is the neutral wire in a 240 circuit the same gauge as both phases (hot wires). Shouldn't the neutral wire be much larger to carry double the current?"

No.

Current in an AC wire "only flows half the time"

If that current can be "filled up" then the wire will be "full".

The 2nd phase wire wills the neutral wire up with a mirror image filling the sine wave gaps.

Three wire to two wire adapter plug test...

Those little plastic adapter blocks that will allow a grounded three wire plug to connect to a two wire outlet is a great diagnostic tool.

You'll need a non contact AC voltage tester for this...

Unplug ANY metal cased appliance then plug it into the adapter then plug the adapter into a wall socket.

Wave the ac detector over the metal of the appliance. If it sounds off there is a fault inside the appliance.

[wa8yxm]

Dangers of open neutral
On a 30 amp RV nothing 120v including the converter works, It is like the breaker is tripped

On a 50 amp RV plugged into 50 amps

50 amp service is 240 volt divided into two 120 volt legs but leg to leg it is 240 volts.

now how they keep the two legs 'Balanced' is the neutral If say one leg is hauling 20 amps and one 10 the neutral hauls the difference (10 amnps) but if the nutral is open, (Floating) then what happens is the "balance" point (Voltage) changes
So you can easily end up with one leg having say 200 volts, and the other 40.. Now on the 40 volt side very little, if anything will work

but on the 200 volt side, The magic smoke may tend to escape from your electronics.. This is not a good thing because electronics work on Magic Smoke. we know this because once it escapes. they stop working.. Stinks too. So if the tester says "OPEN NEUTRAL" well, do not use that circuit.

[road-runner]

This answer assumes you're plugged into shore power or a built-in generator. If you're plugged into a portable generator, there's a very different answer.

The ground connection is also called the safety ground. If absolutely everything in the RV's wiring and electrical devices is working correctly you won't get a serious shock with an open ground. When something isn't working correctly in the electrical system and wants to make the chassis "hot", the ground connection carries the potentially hazardous electricity away instead of it possibly flowing through somebody's body. The bottom line is: If the RV isn't correctly grounded, unplug it immediately and leave it that way until it's fixed. The problem could be in the outlet the RV is plugged into, or in the RV itself. Testing directly at the outlet the RV is plugged into should isolate where the problem is.

The tester is not able to directly determine if the RV is actually grounded. It deduces this condition from the relative voltages on the hot, neutral, and ground wires. There are other conditions that can cause a tester to falsely declare an open ground, but when it indicates open ground, the highest probability is that's what it really is.

[Old-Biscuit]

Simple explanation:

Electric current has to have a path to flow

That path is from the AC source thru HOT wire (Black) then returns on Neutral wire (White) which goes to earth ground.

Ground wire (Green or Bare) is there as a second path to earth ground.
With an Open Ground (No Ground Path) YOU can become the 'path' to earth ground should Neutral path fail
That condition is called 'electrocution'