Grounding Your Camper Part II

Anything electric, AC or DC

Postby asianflava » Fri Mar 31, 2006 2:14 am

Must be this monitor...I'm at work on a shared terminal, they usually get beat up and messed with.
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Postby GeorgeTelford » Fri Mar 31, 2006 3:42 am

Hi TD4

those testers work because the little lights only light with current flowing in the right direction, they are solid wired, with no electrickery how can they possibly go wrong?
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Postby cracker39 » Fri Mar 31, 2006 7:19 am

I don't see any voltage readings on a display either. Is the display toward the bottom of the meter? It's just black on my pics.

TD4, on my meter, I have probes that are red and black. Yours are gray and black. Which one is the Common? In one pic, you have the black to the ground in the receptacle, in another, you have the gray to ground. Doesn't it matter which one goes to the ground and which one goes to the hot? I always put the common (black on mine) to the ground.
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Postby TD4FREEW/CTD » Fri Mar 31, 2006 10:49 am

GeorgeTelford wrote:Hi TD4

those testers work because the little lights only light with current flowing in the right direction, they are solid wired, with no electrickery how can they possibly go wrong?


with the situation i described, i honestly have no idea how they went wrong.

i have also seen them show a grounded recepticle when the ground was in fact VERY poor. the ground light was dim, but it fooled the homowners into believing the ground was good. we ended up openening every single junction box in the entire house and properly connecting the grounds.

Cracker,

my red probe broke. for the function i showed it does not matter which probe is which.
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Postby Ira » Fri Mar 31, 2006 2:44 pm

Man, I appreciate the effort in posting these photos, but I can't see the readouts either. But when George said test the ground, the earth, the soil,and the TD--what does that mean?
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Postby GeorgeTelford » Fri Mar 31, 2006 4:23 pm

Hi Ira

I cant remember asking anyone to test that list.

The pictures show voltage of 115 on top two (exactly where you should see that voltage) and the bottom shows 0 Volts but that could mean that the earth is good and Safe or it could mean the Earth is missing

With one of those tester blocks it would show if the earth was there or missing.

Thats why for the Novice the little tester block is good, plug it in and read off the answer


have a look at this picture, you'll soon get the idea
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Postby TD4FREEW/CTD » Sat Apr 01, 2006 2:33 am

hey telly,

i stick by ma' story! i did a lil research for ya. 8)

i copied all this from this website: http://bg.ecmweb.com/ar/electric_threel ... uit_tester


"Receptacle circuit tester. A device that, by a pattern of lights, is intended to indicate wiring errors in receptacles. Receptacle circuit testers have some limitations. They may indicate incorrect wiring, but cannot be relied upon to indicate correct wiring." (Italics added for emphasis.) Some manufacturers even admit the inaccuracy of the product, printing a disclaimer on the package to caution you of its limitations.

So why are some three-lamp testers ineffective? If you took one of these devices apart, you'd find nothing more than three resistors connected to the three blades of the device. These are ballast resistors, and they prevent each light from burning out when connected across 120VAC.

Two factors contribute to the tester's inaccuracy: circuit wiring capacitance and leakage current from the equipment plugged into the circuit under test. This means the three-lamp circuit testers can provide erroneous indications of the wiring conditions on practically every circuit! To show you the deficiencies of the devices, let's consider these two factors.

Circuit wiring capacitance. Assume you install two conductors for a 120V circuit (a hot and a neutral) and use the metallic conduit as an equipment-ground conductor. The circuit conductor has a distributed capacitance between it and the metallic conduit. If the equipment ground conductor pigtail from the metallic box to the receptacle becomes open, a capacitive voltage exists between the hot conductor and equipment ground terminal at the receptacle. This capacitive voltage causes the tester's lamp (which is connected across these conductors) to light, thus giving an erroneous CORRECT WIRING indication. This open ground condition represents a serious safety hazard during faults, while being detrimental to the operation of electronic equipment. Yet, the three-lamp circuit tester indicates this circuit is good!

Leakage current from equipment. Let's take this a step further. Suppose you connect equipment to the circuit (with the open ground condition). Now, there's no path for leakage current to flow. But there will be one: When you plug the outlet tester into the receptacle. The leakage current will now flow through the lamp connected between the neutral and ground, giving you an incorrect indication of REVERSE POLARITY.

So you follow the tester's indication, and reverse the hot and neutral. Now, you've created an actual reversed polarity. But when you test the receptacle again, the tester indication is CORRECT WIRING.

The original problem was an open ground, and it still exists. Only now, a reverse polarity condition compounds this original problem.

Use a ground circuit impedance tester instead. Your ability to troubleshoot power quality problems on AC wiring and grounding systems is only as good as the tools you use. Instead of choosing the three-lamp circuit tester, use a ground impedance tester. Yes, this more sophisticated device's primary function is to measure the impedance of the equipment grounding conductor or neutral (grounded conductor) from the point of the test back to the source neutral-ground bond. But, it can do additional testing as well:

Detection of wiring errors (reversed polarity, open equipment grounding conductor, and open neutral),


Measurement of voltage, and


Verification of neutral-to-ground and isolated ground shorts.


With this diagnostic tool, you'll get accurate information on which you can base your power quality solutions.

Don't be misled. When checking building wiring, use a ground impedance tester to verify correct wiring and low equipment ground impedances. Use the three-lamp circuit tester as a night-light!
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Postby GeorgeTelford » Sat Apr 01, 2006 6:42 am

Hi

Your average camper is not going to spend thousands on spcialist test equipment to test a campground socket.

I see a bit of self interest there, its in their interests to decry the option that doesnt involve calling an electricion out.

note this sentence

So why are some three-lamp testers ineffective?

So are all indicators useless? I dont think so, now we just need to know which ones work...................
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Postby TD4FREEW/CTD » Sat Apr 01, 2006 5:01 pm

a $10 multimeter from Harbor freight is not thousands of dollars worth of equipment.

all im saying, is if a cheap tester can make you think a ground is there and of good quality, when in fact it is not, which i have seen; then it may be a practical idea to get a cheap meter and learn how to use the thing. its not rocket science. it can save your life.
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Postby GeorgeTelford » Sat Apr 01, 2006 6:12 pm

Hi TD

Sorry they mentioned thousands of dollars

we'll spend thousands of dollars on harmonic analyzers, power line monitors, oscilloscopes, and spectrum analyzers.


You and I can work it out because we know what we are looking for.

But realistically can we teach everybody to use the meter? safely and then read the meter and interpret the results? But in such a way as they will remember?
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Postby TD4FREEW/CTD » Sat Apr 01, 2006 11:42 pm

i dont plan on teaching anyone how to troubleshoot electrical problems. only to show them how to recognize one. all the averaged TD'er needs to know is when NOT to plug in. it is true that more often then not, the plug in tester will give a correct reading; however, it will not show quality of ground and can lead to believe a ground is good when in fact it is useless. its so easy to perform a simple voltage test to ground to verify that your ground is adequate. 90 volts to ground is not adequate, but it will make your plug in tester say so.
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Postby GeorgeTelford » Sun Apr 02, 2006 4:44 am

Hi TD

Would it be true to say that plug tester followed by Earth voltage test would be enough of a safety check?

After all if the Voltage between Live (on the correct pin) and earth is 115 after the socket tester as said correct, would this not confirm everything is OK ? (it would confirm Good earth and Polarity)
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Postby TD4FREEW/CTD » Sun Apr 02, 2006 3:54 pm

GeorgeTelford wrote:Hi TD

Would it be true to say that plug tester followed by Earth voltage test would be enough of a safety check?

After all if the Voltage between Live (on the correct pin) and earth is 115 after the socket tester as said correct, would this not confirm everything is OK ? (it would confirm Good earth and Polarity)


agreed.
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Postby bdosborn » Fri Apr 07, 2006 9:17 pm

Ira wrote:Man, I appreciate the effort in posting these photos, but I can't see the readouts either. But when George said test the ground, the earth, the soil,and the TD--what does that mean?


Ira,

Here's a check list of things I would check before I got the meter out.

- Is the hot on the copper terminal in every outlet?
- Is the neutral on the silver terminal in every outlet?
- Is the ground on the green terminal on every outlet?
- Did you ground the metal box to the green wire for the outlet?
- Do you remember a wire that was hard to pull into a box? Could be you skinned the wire pulling it in?
- Are you sure you didn't connect the neutral and the ground somewhere?
- Did you put a nail or screw *anywhere* near your wiring? ( I drove a screw into a wire even though I was *sure* I would miss it)
- Does your panel have a neutral to ground bond? Seems like I remember a picture of one that had a bond installed from the factory.
- Did you ground the case of your inverter?
- How are your teminations on the receptacles. Could your hot wire be sticking out under the terminal of the outlet and just touching the box?
- Did water get into any of your boxes? The water might conduct to the metal box.

After systematically ruling out any problems by inspecting the wiring then I would move on to the meter. The larger slot on an outlet (left side) is the neutral. Start testing all you outlets like CTD has shown.

Your looking for the following voltages

H-N 120V
H-G 120V
N-G 0V
Write down everything you find and post it so we can all look at it and go from there.
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Postby Jim Marshall » Sun Apr 09, 2006 11:48 pm

I just noticed in bdosborn's post about having the neutral and the ground wire connected at the same place.
"- Are you sure you didn't connect the neutral and the ground somewhere? "

I have installed a breaker box with two breakers. There were two slots for the neutral wires and two slots for the ground wires. The bar for the neutral and for the ground are the same bar, so my neutral and ground wires are connected to the same bar. I thought this is the way they are supposed to be connected. I also have full GFCI connected to everything in our camper including our lights. I did run a ground wire to the aluminum skin of our tear from the breaker box. Did I goof or did I connect correctly?
I started out with nothing and I still got plenty left.

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