Impedance testing

[Vern Mitchinson]

I have been using this “wiggy” for the past couple years ever since AFGI circuits and Ketik water service pipe was approved in Edmonton and area. I visually inspect the panel bonding to the copper water service pipe when copper is used but last week (I do not know why, maybe instinct) I decided to measure the ground impendence on the wall socket next to the main electrical panel. I was shocked (no pun intended) to find 8.04 ohms resistance on the ground. According to the literature that comes with the Ideal meter 0.25 ohms is max for sensitive electronic equipment and 1 ohm for all other uses. This prompted additional testing. I found 9.08 ohms and 4,05 ohms on two addition circuits.
Has anyone else found this?
Should we do more ground impedance testing?
Do you think this procedure be added to the SOP?

[James E. Braun, CMI]

Isn't impedance testing done when you have a hard time fathering children?

[Marc D. Shunk]

Impedance testing is done routinely in the UK, but not so much in North America. I absolutely would not rely on any field ground impedance measurements unless the instrument had a current calibration certificate. The margin of error on an uncalibrated instrument (or an instrument not specifically designed with impedance measurements in mind) can be greater than than the entire range of typical ground impedance measurements encountered in the field.

[Vern Mitchinson]

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I'm using this meter to do the testing and it is accurate.
Has anyone else found this?
Should we do more ground impedance testing?
Do you think this procedure be added to the SOP?

[Marc D. Shunk]

Originally Posted by vmitchinson

I'm using this meter to do the testing and it is accurate.

Maybe it is, but you can't prove it without current calibration.

[Jae Williams]

Originally Posted by jbraun

Isn't impedance testing done when you have a hard time fathering children?

No, Jim...you're thinking of "impudence".

I know it's hindered me on several occasions...back in the day.

[Richard L. Bennett]

Vern

Yes this should be part of sop

Calibration is a question but not a big one -- one resistor that is checked when the meter is just calibrated or new can be checked to be sure it is OK plus the mfg requirements is OK

I started finding ground problems with my eye - then started using a good meter that is 20 years old

I draw the line when neutral and ground are at 0 to .25 ohm (boot leg ground) and neutral to ground greater than 1 ohm

At the breaker box where the neutral and the ground are common .25 is my limit

If I can find a real ground in the home like a water pipe and a ground on a socket that are in reach of my meter leads (kitchen - bath room - laundry - copper pipes) 2 ohms is my limit

Remember that 25 ohm is the magic number for a good earth ground

My home is very much less because of a what I have done to make it so.

How to measure the 25 ohms is outside the SOP because of a lot of BS about how to do it with out spending a lot of $$ on meters and time

Remember that most of our inspections are by eye and time is real short to get an inspection done

A broken or missing ground is easy and fast - A bad one is probably a bad connection that one can wiggle with ones hand

The use of a meter takes time and extra knowledge but I think it should be part of an inspection esp with Florida being the electrical storm area that it is

Trust me after the amount of $$ that I have lost because of electrical storms - good testable grounding is the word

Please understand that DC resistance and AC impedance are not the same and is another thread

Lighting likes low AC impedance and can not be SOP - Too much knowledge training and equipment

Good thread

rlb

[Richard L. Bennett]

Marc

What is this BS?

What is "current" calibration?

One day - week - year - etc. -- and who can do the calibration? - like I can do it myself if I can trace my standards back to the national bureau of standards which is easy

Remember we are only checking one wire for a good connection

rlb

[Richard L. Bennett]

Marc

The proof can be done with a calibration "CHECK" after the test

rlb