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."

trailers by NEC code cannot have the neutral and ground bonded together. Neutral and ground are bonded together at the main panel, but not in the trailer panel which is a subpanel. so, when hooked to most stand alone generators, a meter will indicate ope ground.now, if the meter is indicating open ground on a main panel such as in an rv park or you house, then there is an issue.

Simple explanation:Electric current has to have a path to flowThat 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 failThat condition is called 'electrocution'

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.

Dangers of open neutralOn a 30 amp RV nothing 120v including the converter works, It is like the breaker is trippedOn a 50 amp RV plugged into 50 amps50 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) changesSo 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 workbut 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.

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.

Open-ground hazard | Good Sam Community

30 Replies

MEXICOWANDERER
Explorer
Aug 06, 2017
Wanna hoot? Connect a scope to a microwave that is loading a MSW >50%

140 volt tops would be classified "pipe dream"
road-runner
Explorer III
Aug 06, 2017
MSW peaks vary from model-to-model, and with the DC input voltage. Having said that, after looking at a few of them I think a good generalization for the peak voltage is 140-ish, which is why microwaves run at less than full power with MSW.
time2roll
Nomad
Aug 06, 2017
Actually MSW 120v RMS is likely lower than 177 at peak.
Sine Wave 120vac is 177 at peak.
Harvard
Explorer
Aug 06, 2017
I am with Ktmr, 120V RMS Voltage goes from about +177V peak to -177V peak each cycle....
Harvey51
Explorer
Aug 05, 2017
Ktmr wrote:
120V RMS Voltage goes from about +177 v to -177V each cycle as a sine wave.

I think you mean peak, rather than root Mean square.
ktmrfs
Explorer II
Aug 01, 2017
hedgehopper wrote:
ktmrfs and wa8yxm,

Based on the input from you two, I have determined that the outlet is not connected to a ground wire and is not protected by the adjacent GFCI. The technician who did the installation has promised to correct the problems.

Thank you for your assistance.

glad to see you got it figured out and on the way to a fix.
MEXICOWANDERER
Explorer
Jul 31, 2017
With our tropical salt air, GFCI's malfunction (false trip) all the time. One outside receptacle continued to trip even with a NEMA flapper in place. The bottom line is total sealing. A plug gooped with silicone dieletric grease stuffed into each socket. Life in the tropics.
hedgehopper
Explorer
Jul 31, 2017
ktmrfs and wa8yxm,

Based on the input from you two, I have determined that the outlet is not connected to a ground wire and is not protected by the adjacent GFCI. The technician who did the installation has promised to correct the problems.

Thank you for your assistance.
wa8yxm
Explorer III
Jul 30, 2017
hedgehopper wrote:
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.

It not only has to be on the same circuit it has to be PROTECTED By the GFCI.. How to test for that.

Plug in your 3LT (3 light tester) and note the light comes on, Now go to the GFCI and press the TEST button,,, Are the lights still on. NO Good protected YES not protected.

Now press the Reset (Got to go back in a sec)

Now if it IS down-line from the GFCI (Protected) then here is how GFCI's work

Imagine a Teeter Totter perfectly balanced The weight (Current) on each end is identical One end has a black wire, the other white.. Now so long as the current (Weight) is the same in both wires. it nethier Teeters nor totters it remains flat

But if you add even a single drop of water (Tiny fraction of an ounce or in this case tiny fraction of an ampere) that end goes down and the GFCI is tripped...

So if you go back to my last post.. Had that Skill Hand grinder shorted I would never have felt a ting.. Just tripped the GFCI because it is far more senistive to that imbalance than I am to shock.

That is why they require GFCI in "Wet" places (Kitchen, Bath, Patio)
ktmrfs
Explorer II
Jul 30, 2017
hedgehopper wrote:
myredracer wrote:
OP needs to provide a bit more info

What additional information would you like?

ok,
1) do other outlets on this breaker or other breakers also indicate open ground?
2) when you say shore power, is that connected to 120V at your house or 120V at a campground pedistal?
3) have you verified that on the new outlet that the ground wire is connected to the outlet properly.

Forum Discussion

Open-ground hazard

30 Replies

About Technical Issues

Related Content

Open Ground

Open Ground question

Inverter Installed - Open Ground?

Open ground detected

Portable Generator open ground