Home>Discussions>ELECTRICAL & LIGHTING>Upgrading 2-prong to 3-prong in old 2-wire system
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Re: Upgrading 2-prong to 3-prong in old 2-wire system

Sorry I cant get on everyday and our conversations tend to get drug out but..

I understand How a gfi works.
I understand how potential differences create hazzards

but thanks for explaining that to me.

There are a few key points here I want to restate.

1) there is no EGC between the device (three prong) and the gfi so the GFI would NOT detect a fault current on the EGC if it existed on an appliance plugged into the three prong outlet.
2) I keep hearing that the EGC provides little additional protection.. I disagree .. it enables an appliance to become effectively bonded to other metal non current carrying parts of the electrical system that may become energized.

My point

IMO the NEC has some short comings here. Replaceing a 2 prong with a gfi is great if you cant get a ground to it, but load protecting other devices isnt a great practice IMO. I think your better served pulling a piece of thhn for an egc.

djohns
Re: Upgrading 2-prong to 3-prong in old 2-wire system

Somebody correct me if I'm wrong , but isn't it a code violation to pull a seperate grounding conductor in an attempt to correct the non grounded receptacle issue ?

JLMCDANIEL
Re: Upgrading 2-prong to 3-prong in old 2-wire system
djohns wrote:

Somebody correct me if I'm wrong , but isn't it a code violation to pull a seperate grounding conductor in an attempt to correct the non grounded receptacle issue ?

You have been corrected. It is code acceptable to pull a seperate grounding conductor in an attempt to correct the non grounded receptacle issue.

Jack

Re: Upgrading 2-prong to 3-prong in old 2-wire system
deadshort wrote:

Lloyd, you are contradicting yourself. Any flow out that does not return will trip the GFCI. EGC or not.

More then 5 mA .. I get it. I have two questions tho

1) 5mA at what voltage and respect to where?

2) hypothetical; 4mA fault current on the EGC at 120 volt, not enough to trip the GFI. Change the respect from the ungrounded conductor to say the metal part of an appliance on a different circuit QUESTION 2 What potential voltage could be present?

My point (again) and I stand by it, your undervalueing the EGC on a gfi circuit. It still acts to bond metal non current carrying parts, like the metal parts on a ceiling fan or appliance...

IMO load protecting a threeprong outlet and putting a sticker on it is a bad practice. I could understand load protecting a 2prong outlet ...a sticker isnt a ground gfi or not.

also

neither the EGC or the GEC(system) are intended to serve any function having to do with lightning protection or noise filtering. The sole purpose of the two systems is to dissipate fault current and bond non current carrying parts (to dissipate fault current) thus respectfully THE MOST important part of any electrical system. To suggest you are SAFER with a gfi and no EGC is IMO less then accurate.

neither GFCI devices or breakers are intended as PERSONAL safety devices (check the whitebook) (not to mention one of the most unreliable pieces of equipment in the industry ... look at the fail rate)

Jack / Ernie / canuk, dont take me wrong I have nothing but respect for you and I'm not in anyway trying to flame you

JLMCDANIEL
Re: Upgrading 2-prong to 3-prong in old 2-wire system

Lloyd take a look around your house and see how many appliances have a 3 pronged plug on them. Computers and power strips because it is necessary for noise and spike filtering. (Sorry I designed electronic equipment and know why the ground is required) Even wall warts. Refrigerator, washer/dryer, and microwave because they are required (from the beginning of code enforcement)because they are installed in a kitchen or wet area.

If a GFCI fails, it can't be reset. No danger. If the ground wire connector corrodes or is broken. No safety and the fault is almost always hidden.

If a hot wire in a micro gets shorted to the case and the ground is missing or defective and you touch it and a water line the GFCI will prevent injury and damage to the microwave. I it is grounded and no GFCI you would have a direct short that would trip the breaker, however you would produce a 2400 watt (120v X 20 amp)spark that could burn out wiring, melt wire insulation, or cause a fire.

Jack

Re: Upgrading 2-prong to 3-prong in old 2-wire system
deadshort wrote:

So, set up a scenario, please, where there is less than 4mA of "leakage" on any circuit protected by a standard non GFCI breaker. Then tell me how anyone is better protected.

Deadshort
My point isnt wether a gfi or a ground provides better protection, but rather wether a 3pronged outlet should be allowed to be load protected by a gfi with no egc present. (I admit the egc between the gfi and load protected device would serve no purpose) In this case a 2pronged outlet (soley) should be required. BECAUSE THE OTHER FUNCTION OF THE EGC IS TO BOND METAL NON CURRENT CARRYING PARTS. I think this second function is being undervalued.

What provides better protection?

standard breaker with ground

gfi breaker and no ground

gfi breaker and a ground

obviously a gfi w/ground right? (if not why would the nec even require a ground)

what is more UNSAFE the above 3 scenarios or

a gfi protected circuit where someone beleives an egc IS present?

Jack
Of course the ground performs other functions noise filtration one of them, but that isnt why its there. When you designed electronics I assume there was a grounding system in the factory you worked that you plugged your wrist straps into, was that system tied into the egc or gec? (rhetorical) Or was it installed as a seperately derived system with its own gec (system) bonded to the service ground and used specifically for esd protection devices like wrist straps and the like?

buffyscrubs
Re: Upgrading 2-prong to 3-prong in old 2-wire system

I believe the NEC just is covering all the bases on this one.

-------------------------------------------------------------------
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Nip Tuck box set

JLMCDANIEL
Re: Upgrading 2-prong to 3-prong in old 2-wire system
Lloyd wrote:

Deadshort
My point isnt wether a gfi or a ground provides better protection, but rather wether a 3pronged outlet should be allowed to be load protected by a gfi with no egc present. (I admit the egc between the gfi and load protected device would serve no purpose) In this case a 2pronged outlet (soley) should be required. BECAUSE THE OTHER FUNCTION OF THE EGC IS TO BOND METAL NON CURRENT CARRYING PARTS. I think this second function is being undervalued.

What provides better protection?

standard breaker with ground

gfi breaker and no ground

gfi breaker and a ground

obviously a gfi w/ground right? (if not why would the nec even require a ground)

what is more UNSAFE the above 3 scenarios or

a gfi protected circuit where someone beleives an egc IS present?

Jack
Of course the ground performs other functions noise filtration one of them, but that isnt why its there. When you designed electronics I assume there was a grounding system in the factory you worked that you plugged your wrist straps into, was that system tied into the egc or gec? (rhetorical) Or was it installed as a seperately derived system with its own gec (system) bonded to the service ground and used specifically for esd protection devices like wrist straps and the like?

Lloyd,
If you stop to think about it, if it wasn't for the fact that the utility company grounds the neutral at the pole for lightening protection no grounds would be needed at all. If one leg was not grounded you would get no current flow to ground on any leg because it would not supply a return path necessary for current flow.
Jack

Re: Upgrading 2-prong to 3-prong in old 2-wire system
JLMCDANIEL wrote:

Lloyd,
If you stop to think about it, if it wasn't for the fact that the utility company grounds the neutral at the pole for lightening protection no grounds would be needed at all. If one leg was not grounded you would get no current flow to ground on any leg because it would not supply a return path necessary for current flow.
Jack

The function of the circuit ground or grounded conductor whatever you want to call it is completely beside the need for the equipment ground.

Teach me something Jack, show me why the only purpose of the ground rod on the pole is lightning protection.

JLMCDANIEL
Re: Upgrading 2-prong to 3-prong in old 2-wire system

What other purpose does it serve? None. But because the neutral is grounded at the transformer, ground becomes a return to the transformer. Without that connection and the ECG connection at the panel, ground would not provide a return. In that case if you touched a hot wire to ground nothing would happen. If you had a hot shorted to the case, of say a washer, and you touched the case and a water pipe you would not get shocked. The only purpose of the ECG is lightening protection, and bonding is a compensation for a problem the lightening protection causes. A GFCI dose a much better job because it dose not require 15 or 20 amps to react.
Jack

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