symptoms of a weak Ground.

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troberts2007

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Location
Trussville AL
I had a home owner who was using one of the 3 light receptacle checkers to test plugs in his home, he thought he had a neutral ground reversal because of the light pattern. I went onsite to repair but I noticed the middle light on the tester was not at full brightness but was definitely turned on. as I was searching I removed a receptacle from the circuit the tester went from neutral ground reversal to missing ground. and sure enough we found a broken ground in the first box from the panel so nothing down stream would have had a ground. I re[paired the ground and everything tested ok the rest of the way. but the original problem still has me puzzled on why the tester was showing a partial ground neutral reversal. and my only thing I can think of is possible a back feed from the neutral to the ground at the panel and that maybe the Panel isn't fully grounded and that maybe we should add a 2nd ground rod. Does that sound reasonable?
What are the other symptoms of a panel that isn't properly grounded or has a weak ground.
 
J

JFletcher

Senior Member
Location
Williamsburg, VA
troberts2007 said:
I had a home owner who was using one of the 3 light receptacle checkers to test plugs in his home, he thought he had a neutral ground reversal because of the light pattern. I went onsite to repair but I noticed the middle light on the tester was not at full brightness but was definitely turned on. as I was searching I removed a receptacle from the circuit the tester went from neutral ground reversal to missing ground. and sure enough we found a broken ground in the first box from the panel so nothing down stream would have had a ground. I re[paired the ground and everything tested ok the rest of the way. but the original problem still has me puzzled on why the tester was showing a partial ground neutral reversal. and my only thing I can think of is possible a back feed from the neutral to the ground at the panel and that maybe the Panel isn't fully grounded and that maybe we should add a 2nd ground rod. Does that sound reasonable?
What are the other symptoms of a panel that isn't properly grounded or has a weak ground.
Click to expand...

Which brand/model of tester? They all have different light combos for the various miswires, but no plug tester can find ground/neutral reverse.

Before you think about checking the panel, use a multimeter to check your receptacles instead of the 3 prong plug in, which can give erroneous readings on certain miswires.

Adding another ground rod is not the way to proceed.

eta: weak grounds typically give less than 120V readings from H-G, and the numbers on the DMM can 'float' or jump around. Cheap testers can also show a good ground when there isnt one:

https://www.youtube.com/watch?v=rF0mcq6BRDk

and cant find bootleg grounds:

https://www.youtube.com/watch?v=XfAPkJVYUpY
 
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kwired

kwired

Electron manager
Location
NE Nebraska
jumper said:
Those doohickey testers cannot show a ground-neutral reversal IIRC. How could they know?

Driving a ground rod to solve an unknown problem is silly. Solves nothing.
Click to expand...
They possibly could detect lower voltage to the EGC then to the neutral but still isn't complete assurance of N-G reversal, just means that there is more voltage drop on the EGC terminal when if anything more drop is expected on the neutral.
 
don_resqcapt19

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
peter d said:
:thumbsup:

I wish more electricians understood this. So many misconceptions about grounding/earthing and bonding lead to unnecessary overkill.
Click to expand...
The overkill is not a problem other than an economic one, but you can think the problem is gone because you added some bonding and or grounding, but often you have just masked or covered up the problem...not fixed it.
 
peter d

peter d

Senior Member
Location
New England
don_resqcapt19 said:
The overkill is not a problem other than an economic one, but you can think the problem is gone because you added some bonding and or grounding, but often you have just masked or covered up the problem...not fixed it.
Click to expand...

I'm aware of that, you basically proved my point. Overkill is not a problem, but neither is it a solution.
 
al hildenbrand

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
troberts2007 said:
. . . we found a broken ground in the first box from the panel so nothing down stream would have had a ground. . . . only thing I can think of is possible a back feed from the neutral to the ground at the panel. . .
Click to expand...
The three light polarity tester was plugged into the branch circuit downstream of the break in the equipment grounding conductor (EGC) in the first box, so the tester can't "see" the panel on the EGC. The panel is the wrong direction to look, from the break in the EGC.

The weakly glowing EGC "OK" indicator light in the tester does see the floating section of the EGC that is downstream of the break in the first box because it is electrically connected directly to it at the plug the tester is inserted in.

That floating section of downstream EGC is connected to the device yokes and other metal parts like light fixture bodies. . . and what are they touching? What other grounded conductive surfaces are in the vicinity?

If any three wire cords (with EGC) were left plugged in while the tester was used, "bleed through" inside the load between the neutral and the EGC could be the source of the "weak ground". Worn lamp holders in metal shells, pinched wires. . . all kinds of possibilities for a high resistance path to actual good electrical return paths, ALL on the downstream side of the first box break in the EGC.
 
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