I just moved into a place with no 3 prong outlets outside the kitchen. I need to change at least some of the outlets to 3 prong in order to hook up my computer and my TV.

I've read that you can use a GFCI to replace the two prong with minimal safety sacrifice and without having to run a ground wire. Is this remotely correct / safe?

6/20/2008 3:06:27 PM

there's none in the bathrooms either?

old house?

6/20/2008 3:07:59 PM

Kitchen and bathroom both have 3 prong, but no GFCI.

The rest of the house is 2 prong. It is actually an older townhouse that I'm renting for only 6 months, so I'm looking for a safe but low-key solution.

6/20/2008 3:10:05 PM

i would just buy adapters; safety isn't really that big of an issue for the tv or computer

[Edited on June 20, 2008 at 3:12 PM. Reason : there might be ground fault breakers for the kitchen & bath]

6/20/2008 3:11:31 PM

me not fucking up my computer is an issue.


And no, there are no GFCIs anywhere in the house. Which surprised me.

[Edited on June 20, 2008 at 3:17 PM. Reason : .]

6/20/2008 3:12:27 PM

it shouldn't matter

[Edited on June 20, 2008 at 3:35 PM. Reason : GFCI's don't have to be in the receptacle, it can be in the actual breaker]

6/20/2008 3:12:53 PM

I'm curious, for a 2000 sqft house with about 30 outlets how much would it cost to have the old two prong outlets upgraded to three prong outlets?

Any electricians care to offer an opinion.

You may assume that there are several three prong outlets downstairs, but only in one room.

6/20/2008 3:46:03 PM

I am going to have to put one in the kitchen of the house I am about to buy. Hopefully it is a cheap fix. If it is, I can get the previous owners to focus on other fixes around the house....

6/20/2008 3:49:22 PM

^^if depends on the way it's done; if there's already a grounding path there, it's basically just a matter of replacing the receptacles. if not, you can replace them all with GFCI, which costs more; or have new wiring put in, which costs a lot more

6/20/2008 3:55:18 PM

^what he said.

basically the only way it's gonna be cheap is if you have metal j-boxes & metal conduit, allowing the ground wire to be wired to the box w/out running a ground wire all the way back to the breaker

i just had my 1200sf house done (1915 bungalow) and there was only like 15 receptacles in the entire house. cost me $200 to have them swapped out for 3-prong.

basically if you are renting, just buy the adapters, the only reason you need a ground anyways is in case lightning strikes or there's some sort of power surge from the power going out. if it's t-storming outside, just shut your high-end electronics off.

6/20/2008 6:04:39 PM

just break the third prong off from your power cords so they will fit.

6/21/2008 9:19:48 AM

run a bunch of extension cords from the kitchen to your electronic equipment

6/21/2008 9:43:23 AM

but the kitchen is two plug. Yarg.

6/22/2008 1:48:36 AM

break off the third prong

6/22/2008 11:45:48 AM

break off the third prong

6/22/2008 12:05:53 PM

get these

http://www.73.com/a/mf756.gif

screw that wire onto the screw holding the socket cover in place. =grounded

6/22/2008 12:12:57 PM

You may get lucky with one of those ^. Buy one of these http://www.mytoolstore.com/ideal/ide05-08.html to test it. This only works if the box is grounded. Don't get your hopes up.

Also test your 3 prong outlets in the kitchen. Sometimes people swap out 2 prong for 3 prong without properly grounding.

A surge suppressor well not function properly on an ungrounded circuit.

GFCI well not protect your equipment.

It sounds like you need to hire an electrician at some point assuming you own the place. The old wiring should be checked by a professional anyway.

6/22/2008 3:48:07 PM

and pray you don't have aluminum wires

6/22/2008 3:50:36 PM

why are Al wires bad?

6/22/2008 7:58:33 PM

Lots of reasons... its not really so much in the cable itself, but where the cables join and connect to devices. aluminum cable expands more than copper as its heated which can loosen connections. over time loose connections can arc and cause fire. copper oxide acts as a conductor whereas aluminum oxide serves as a resistor. this makes aluminum cable hotter especially at the connection joints. you can also get some galvanic corrosion when you join aluminum to copper cable. there are types of connectors that use an antioxidant to prevent corrosion of the connection, but still if not evenly applied it can corrode.

you will find houses that have aluminum wire several times more likely to burn down than those with copper wire.

6/22/2008 8:26:34 PM

interesting

6/22/2008 8:32:35 PM

(1) GFCI receptacles/breakers are designed to prevent LOSS OF LIFE.

(2) GFCI receptacles, when properly installed, do absolutely nothing to protect electronic equipment.

(3) GFCI receptacles will not work properly (ie, protect against loss of life) in an ungrounded receptacle box.

(4) the fact that you have 2-prong receptacles makes it HIGHLY UNLIKELY that your receptacle boxes are grounded.

(5) the only way your receptacle boxes are going to be properly grounded -- that is, to the EARTH GROUND -- is if you have a 3-wire electrical system in your house, with a separate grounding electrode conductor. which you obviously do not.

(6) the 3-prong converters with the grounding pigtail such as tchenku posted are absolutely worthless since your receptacle boxes are ungrounded.

(7) the only thing that will protect computer equipment are surge protectors

(8) like GFCI's, surge protectors rely on the grounding electrode conductor (the "green" ground, NOT the neutral) to work properly.

if you have bypassed a 2-prong receptacle in an ungrounded 2-wire electrical system (such as with one of those adapters), then No Amount of Surge Protection Will Ever Work

....

if you are renting, it is the LAW that your landlord be UP TO DATE on the National Electric Code. force them to upgrade if they are not.

if you own your house and it's out of date, it's up to you to get it fixed yourself. the law does not require that you do so, unless you are making improvements or subletting.



CONCLUSION:

hire an electrician to do this work. do not attempt to do it yourself if you don't know what you are doing.






[Edited on June 22, 2008 at 9:18 PM. Reason : ]

6/22/2008 9:02:25 PM

Quote :

"(2) GFCI receptacles, when properly installed, do absolutely nothing to protect electronic equipment."

that's not true. residual current devices (aka gfci, gfi, whatever) can be used to protect both people and equipment. the NEC mandates that people-protecting rcds trip in the 4-7 mA range. larger equipment-protecting rcds trip in the 30-50 mA range, and even up to the several amps range for machinery (set by the IEC i think).

Quote :

"(3) GFCI receptacles will not work properly (ie, protect against loss of life) in an ungrounded receptacle box."

yea, they will. rcds check for a current imbalance between the phase and neutral conductors for some improper flow of current to ground, whether it be a ground conductor or through a human. two-wire receptacles can be replaced with a gfci to protect a person from electrocution, as it will still function without a ground conductor connected to it.

6/22/2008 9:45:59 PM

with all due respect, joe, i think your work in heavy industrial power generation facilities is causing you to miss the point.

GFCI -- ground fault circuit interrupters -- the residential receptacles or breakers, detect an increase current between the current-carrying conductor and the grounding electrode conductor. the kind of current changes that occur when a person is going to get electrocuted at the bathroom sink, for instance

Surge Protectors are designed to prevent against voltage surges that blow holes in semiconductors without any measurable change in current flow. actually, the current would decrease, if anything. a GFCI is worthless in this situation.

what we're talking about is low voltage residential use -- not power substation industrial applications. And both of these devices require the grounding electrode to be connected to earth ground to work properly.






[Edited on June 22, 2008 at 10:24 PM. Reason : ]

6/22/2008 9:57:06 PM

oh god an asshole programmer and a nice guy electronerd

FIGHT

6/22/2008 10:02:46 PM

Quote :

"GFCI -- ground fault circuit interrupters -- detect an increase current between the current-carrying conductor and the grounding electrode conductor. the kind of current changes that occur when a person is going to get electrocuted at the bathroom sink, for instance"

no. gfcis operate by detecting an imbalance between two conductors (phase and neutral) using a differential current transformer, and opening up the devices contacts (by use of a solenoid) if there is such an imbalance.

you are right about surge protectors trying to block or shunt unsafe voltages caused by some transient to ground (by use of mov's (metal oxide varistors)).

6/22/2008 10:03:42 PM

No, Joe.

I have read up on how GFCI's work for many years, first in my several years as a journeyman electrician, then as an electrical system designer for an engineering consulting firm.

GFCI's work by explicitly sensing the amount of current flowing between the current-carrying (HOT) conductor and the grounding electrode (GREEN/ground) conductor.

The current between the current-carrying (HOT) conductor and the grounded (NEUTRAL) conductor is irrelevant -- it could be the amount required to drive the device -- what's critical is whether or not the operator is getting his ass electrocuted at the same time, and that is the current going from HOT to GROUND. Hence, "ground fault".

the GFCI can only work, if the the Grounding Electrode Conductor is properly connected to EARTH GROUND.

I think you are missing the difference between "grounded conductor" (NEUTRAL) and "grounding electrode conductor" (EARTH GROUND).

this is a common mistake made by many people, even some electricians and engineers.

please consult the NEC Article 250.







[Edited on June 22, 2008 at 10:30 PM. Reason : CLARIFIED neutral current vs. ground current]

6/22/2008 10:13:52 PM

I'm actually surprised to see a legitimate debate go this long without one guy calling the other a dumbass

article 250 deals with grounding and bonding. you're right that in the us neutral conductors are bonded to a grounding electrode at the service entrance (and also at the distribution transformer). article 210.8 is about gfcis for personnel safety

however, a gfci directly senses a current imbalance between a phase (hot) conductor and neutral conductor. in many instances the leakage current going through a person can then pass to the ground conductor, because most people get shocked when touching the faulty device's enclosure which ideally should be tied to ground. but it doesn't always have to be that case. the path to ground through a person could continue through a water faucet or anything at a lower potential than the person experiencing the shock. by your explanation of a gfci, if the current doesn't go through the grounding conductor then it will continue to operate normally.

here's a nice diagram i pulled (borrowed) from the 2005 nec. i don't have the 2008 pdf version yet.


from the diagram above, in normal operation, current in = current out. therefore the 'sensor,' essentially a current transformer senses nothing since the vector sum of the two currents is zero. when a person is getting shocked, some of that current is going somewhere else therefore current in =/= current out. the vector sum of the two currents is not zero which causes the gfci to react and open the circuit.

on that note, i just took some hydrocodone and an ambien, so goodnight folks.

6/22/2008 11:11:12 PM

dumbass



[Edited on June 22, 2008 at 11:20 PM. Reason : ]

6/22/2008 11:19:08 PM

okay Dr. Joe is right, GFCI's don't require grounding conductors to work properly. my original point # (3) is wrong.

in hindsight, i knew this at one time. ive been out of the electrical systems industry for 4 years. i need to re-check my facts more, and argue less

still, (and i've gone back and checked) the rest of my points remain:

-- you need a surge protector (not GFCI) to protect consumer electronics

-- a surge protector will NOT work with an ungrounded electrical system

-- 2-prong to 3-prong converters with pigtail grounding conductors are worthless -- you'll still have an ungrounded electrical system ... the same effect if you just cut the 3rd (ground) prong off your electrical cords.

the reason is there's no path to ground. most residential electrical boxes are plastic or fiberglass, and even if they're metal, they're just nailed to wood 2x4. you dont have metal conduit systems connected to metal framing in your house/townhome/apartment. in a commercial building, yes. residential building, no.







[Edited on June 23, 2008 at 10:01 AM. Reason : ]

6/23/2008 9:40:42 AM

I'm glad that the work I do for clients is typically NEC exempt.

6/23/2008 12:48:35 PM

nicely played argument, gentlemen.

6/23/2008 1:08:02 PM

Quote :

"i need to re-check my facts more, and argue less"

too much time in TSB will do that to you

6/23/2008 2:11:28 PM

werd to that.

6/23/2008 2:29:28 PM

The Joe's are my heroes.

6/23/2008 2:35:47 PM

or he could just break off the third prong

6/23/2008 3:36:51 PM

well, that's what i would do.

6/23/2008 4:41:23 PM

^

6/23/2008 4:47:37 PM

Quote :

"dumbass "

Quote :

"i think your work in heavy industrial power generation facilities is causing you to miss the point."

Quote :

"okay Dr. Joe is right"

Quote :

"I have read up on how GFCI's work for many years, first in my several years as a journeyman electrician, then as an electrical system designer for an engineering consulting firm. "

Quote :

"ive been out of the electrical systems industry for 4 years."

hindsight's a bitch, isn't it?

Quote :

"this is a common mistake made by many people, even some electricians and engineers."

true. me being an asshole for the dumbass comment aside, this stuff isn't easy and it's very simple to get confused. it sounds like you know (most of) your stuff. i agree with your points about surge protection. gg, this was fun

6/23/2008 6:08:14 PM

i HATE THAT PIC, always have

red dude already won long ago

6/23/2008 6:36:42 PM

Quote :

"oh god an asshole programmer and a nice guy electronerd FIGHT"

LMAO

6/23/2008 6:37:10 PM

Quote :

"it sounds like you know (most of) your stuff"

when in doubt, sound like you know what you're talking about.

there will always be time to shift blame later.

6/23/2008 7:07:26 PM

So, if you ran a ground from the outside throughout the house to the places you wanted to upgrade the 2 to 3 prong outlets then just wired in the earth ground to supplement the existing 2 prong outlets wiring would this work?

BTW, I have enjoyed the great GFCI debate above, and not just because joe_schmoe lost.

6/23/2008 9:55:34 PM

idk why not

6/23/2008 10:35:06 PM

joe#'s why do you have time to argue with yourself in the lounge but you dont post the average AC power formula for the guy in tech talk? power factor is like your bread and butter

6/24/2008 12:52:01 AM

Quote :

"So, if you ran a ground from the outside throughout the house to the places you wanted to upgrade the 2 to 3 prong outlets then just wired in the earth ground to supplement the existing 2 prong outlets wiring would this work?"

that would be the very definition of some jackleg bullshit.

"safe", "legal", "craftsmanlike", "will work"

one of these things doesnt belong here...

6/24/2008 12:57:59 AM

Quote :

"joe#'s why do you have time to argue with yourself in the lounge but you dont post the average AC power formula for the guy in tech talk? power factor is like your bread and butter"

a link to said thread would be nice... and clearly i have been arguing with myself

6/24/2008 7:31:28 AM

i was wondering about that .....

6/24/2008 11:56:26 AM

Quote :

"that would be the very definition of some jackleg bullshit. "safe", "legal", "craftsmanlike", "will work" one of these things doesnt belong here..."

idk how you figure that a separate grounding wire is any less safe or legal than using romex

6/24/2008 6:55:44 PM

Well, I suppose my basement has a drop ceiling so I probably could just run new wire from the box without too much trouble now that I think of it. I will admit my previous suggestion, while physically reasonable, is probably not up to "code". I've had courses on industrial electronics a while back, so I kinda know what's the deal, but I thought if I ran it by TWW then if something is wrong with my idea then I would at least give another user the joy of winning on the internet.

6/24/2008 11:04:31 PM