Ungrounded Recept

MSSI

I cant find anyting in 2005 that says I must have a grounded receptacle if the circuit has a ground...
My realator friend called me and said they switched all the recepts. to 2 prong even though there is a ground avalable...

Her Engineer husband thought you had to, becuase the old ground wires were insufficient..After a chuckle or two I told her Ill check... The home inspector says they must change em to grounded recepts.

What do you guys think?????

Cole

Why would they make the switch to 2 prong?

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MSSI

Thats what I asked...I never had to argue it this way...Its usually about trying to put 3 prongs into a ungrounded circuit...

I guess somewhere along the line when selling a house they were told to switch to 2 prongs. (probably for the obvious) so when they rehabbed this one they changed em ALL to 2 prong......If I was buying the house I would want em to change them back as well..Bottom line is they didnt know what the hell they were doing,,,but since they have been a help to me in the past I told them I would check to see if they have an arguement to leave them as is....

mdshunk

406.3 General Installation Requirements. Receptacle
outlets shall be located in branch circuits in accordance
with Part III of Article 210. General installation requirements
shall be in accordance with 406.3(A) through (F).
(A) Grounding Type. Receptacles installed on 15- and 20-
ampere branch circuits shall be of the grounding type.
Grounding-type receptacles shall be installed only on circuits
of the voltage class and current for which they are
rated, except as provided in Tables 210.21(B)(2) and
(B)(3).

Sparky Joe

A good question is how would they be deemed insufficient?

A low impedance ground path is the goal, but at what point does the impedance of the ground wire gauge become a hazard?

MSSI

Thanks again MD....I just skipped right over that part..Duh I was whipping through looking for "un grounded circuits" to pop out at me.........

jbfan

Could it be that it is an older house with undersized grounds.
That may be why he thought the grounds were insufficient.

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mdshunk

I've seen people "rewire" a house, but they continue to use the ungrounded home runs. The appearance of a ground wire at the receptacle doesn't necessarily mean it's hooked to anything at the other end.

Sparky Joe

My point exactly

If the ground wire is way undersized and poses too much resistance to trip a 20 amp breaker, it then becomes a bigger hazard than having no ground wire at all by energizing the entire grounding system

Bubbles

Couldn't you just ring out each receptacle from ground to neutral. If you get 0 then put a 3 prong. if its over 20ohms or so put the 2 prongs in ???? Just a random thought.

neolitic

If it's old work with flex conduit, I've been grounding to a bond screw in the steel box if I read continuity to the panel. Is this wrong?

JohnJ0906

20 ohms would be way too high.

120/20 ohms = 6 amps. That's not tripping any breakers.

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All replies based on the 2008 NEC

Sparky Joe

Again the "sufficient" question comes to play. 4 ohms would draw 30 amps and may trip a breaker in 2 minutes, but again is that sufficient?

mdshunk

Depends on what you're calling "flex conduit". The sheath of the old type AC cable without the thin aluminium sheath bonding strip inside (pre-1957 or thereabouts) is not and never was rated for use as an equipment grounding conductor, regardless of what shows up on your ohm meter.

Magnettica

406.3 (D)(3)(b)... tells me, where a grounding means does not exist (the box) to change a non-grounding receptacle to a GFCI type. I had to do this earlier this week.

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neolitic

Thanks for learnin' me somethin'. I always figured all that steel was as good as those little #18 or whatever it was in that early romex stuff. Now on I'll take the three holers with me when I'm done plugging my cords in.Just leave the folks with new old.