Because it is the CORRECT "low impedance" multimeter that can accurately measure line voltage circuits...
The cost is irrelevant, as long as the multimeter is the correct type, you will be able to properly measure for the actual presence or absence of hazardous line voltages...
As others have stated, use an incandescent test light or analog meter to test voltage to "ground." I bet there really is none. This is not a "problem" per se but you really should be using GFCIs on any ungrounded circuits with grounding type receptacles.
Three breakers for the A/C sounds hinky though. You should have one double breaker for the A/C, period. If you can't figure that one out yourself, you may wish to call an electrician to look at it - something ain't right there.
There have been several (correct) attempts at an explanation. As I read your experiment, you tried on a correctly wired circuit and got correct readings. Just what you would expect.
Now, go unhook your ground wire at the panel. The hot line will induce a voltage in that wire that can be read by a high impedance meter as difference in voltage between ground and neutral. Is that plausible?
Why not? You've got the floating wire lying right next to a 120v line for 50 feet or whatever the distance to the panel is. The voltage will be some large percentage of 120v. The current will be tiny (which is why DMM's show the voltage and analog meters don't). -- Doug
Not only is cost irrelevant, but it's also a function of the person using the meter understanding some basic electricity and knowing how to interpret the readings. I've exclusively used digital VOMs for decades and never had any confusion. You could also make up an extra set of test leads with a 50K ohm resistor across them to reduce the input impedance.
Sometimes they are. I have never used the Klein tester but can see where it may be a much beter circuit tester than some meters. Only problem is that it is a $ 50 or so tool where the meters can be bought for $ 5 to $ 20 and be used for more things. A good old low power light bulb is very useful to run some checks with around the house.
For quick checks where I work I have a Fluke tester that is sort of like that. You just hook it up with the two test leads. If it is AC then anything from 24 to about 600 volts will light up some leds. It is DC then other lights will glow from about 12 volts up. And if there is a very low value resistance, another light will glow. Comes in handy for quick test when I may be working on some of the computer controlled equipment and may need to know if I have a relay contacts closed, or 24 volts , 120 volts or
480 volts active.
One thing I did not mention is that on a Simpson 260 and probably others like it is that if you suspect a phantom voltage you can move from one range to another and the meter will stay in about the same place on the scale. If the voltage is a solid voltage then the meter will go up or down a good bit to match the voltage with the scale on the meter.
The neutral is supposed to be grounded at the panel That holds the neutral to ground potential. If the neutral is not grounded it can be either high or low from ground (the ground can be at a higher potential than the neutral due to ground leakage) Quite common in rural areas - where you can sometimes get a shock from a safety grounded device to "eath ground" - and cattle will stop drinking from their water bowls because the grounded bowl and earth ground are at different potentials - giving them "discomfort" when drinking.
If the "long runs" were live, there is no reason the readings would not be accurate. However, a long run with a "dead" circuit paralleling a live one MAY read a voltage that would lead you to believe the circuit was connected and had a problem. If, in the OP's situation, for instance, the ground conductor actually DID exist, but was not connected to the panel ground, it is possible a "sensitive" or high impedence digital (or even VTVM) meter could indicate a voltage between the ground and either power-carrying conductor.
If it doesn't light up visibly, but the voltage is still there (ANY voltage) it's still a problem. If the voltage is ZERO, it most likely is not a problem - just inductive or capacitive coupling.
Three double pole breakers can be quite normal for a heat pump compressor, it's air handler, and it's supplemental resistive heating elements. Two double pole breakers could be normal for a central air conditioning compressor, an air handler, and a condensate lift pump or other accessory. Are the three breakers single or double pole. What are the breakers ampacities.
On 4/3/2010 5:13 PM snipped-for-privacy@snyder.on.ca spake thus:
The tester would expect ground to be at or about at the same potential as neutral. That's as far as it can go, and as you point out, it can't really determine the "goodness" of the ground, only whether it's present and close to the neutral potential.
I never had a 3 lite tester until rather recently. The package explicitly said it would not determine if the ground was good. Also doesn't determine if hot or neutral are good, but you can tell when you use the outlet.
There are other possibilities. Like if there is no ground and an idiot wires a receptacle neutral to the ground, and then an idiot - the same or new - replaces a receptacle upstream and accidentally swaps the hot and neutral. The 3 lite tester will show the receptacle with a hot ground as OK. Real unlikely, but ....
One advantage is a Wiggy is pretty indestructible, as from drops, compared to a meter. I tend to use a neon test light for things like receptacles, partly because you can tell what wire is hot and it takes no space in my pocket.
Particularly after reading about arc-flash and 'sudden reconfiguration of the physical parts of a meter syndrome' I am more careful what I use. Measuring at a receptacle is not so bad, but I want something good if I am in a service panel, and something real good at high energy locations
- 480V or high amps. There is a category rating for meters - Fluke (and others) use it.
Yea - simple but effective.
Ran across that once and it was one of more bizarre measurements I have seen.
Now days, kids who grow up without electricity. and just look at them. Baseball hats on sideways, and droopy pants with underwear showing. Some of them, I'd like to hook them up to the 220 volts until they shape up.
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