dslreports logo
site
 
    All Forums Hot Topics Gallery
spc

spacer




how-to block ads


Search Topic:
uniqs
6501
share rss forum feed

iLearn

join:2013-01-16
canada

First post - recently joined - GFCI without a ground wire

Hi guys,

I was referred to this forum and thought I should make my first post with a question.

I know a little but about home system and home improvements in general but I would like to learn more from people on this forum.

My first question is do we need a ground wire to make an outlet GCFI protected? I have heard mixed opinions on this and wanted some feedback on this.

A friend of mine just moved to an older house and he was told that he can install a GFCI outlet in the kitchen where is no ground.

Can someone please clarify?

Thank you



leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET

Yes, it is perfectly safe and legal to install GFCI outlets on circuits without a ground wire. There is a requirement to mark those outlets with the text "No Equipment Ground" (stickers are often included when you buy a GFCI outlet).

Because a GFCI measures the differential in current between hot and neutral there is no requirement for a ground wire. Note that a GFCI without ground only provides safety against personal injury. If you have the rare situation of equipment that requires grounding for other purposes such equipment may not function properly (e.g.: ground for interference shielding).
--
Got some spare cpu cycles ? Join Team Helix or Team Starfire!



LazMan
Premium
join:2003-03-26
canada
reply to iLearn

Welcome to the board...

Yes, it's acceptable to use a 3 prong GFCI outlet in a non-grounded application; as long as that outlet, and any downstream are labelled "No Equipment Ground".

The GFCI will provide improved safety, but it doesn't magically create a ground, either.

It's far better then just replacing an ungrounded outlet with a 3 prong, and leaving the ground open, or using those 2-3 prong 'cheaters'. Best option is always to replace the ungrounded circuit with proper grounded circuit, but that's not always an option...

All that said - typically in Canada, kitchen outlets are either 15A split receptacles (meaning the connecting tab is removed on the 'hot' side, and there's 2 x 15A fuses or breakers feeding the outlet) - or are on 20A circuits. If it's a 20A circuit, it should be new enough to be grounded. It's a 15A split, there's no way to replace it with a GFCI... They just don't make such a beast.


iLearn

join:2013-01-16
canada
reply to iLearn

Thanks leibold and LazMan.

@ leibold - I wanted some clarification, you said 'differential in current between hot and neutral', do you mean differential in voltage instead? I am saying this because as far as I know, the neutral carries the different between the current coming in through hot and the amp (current) used by the resistance (a bulb for example). So the current flowing through the neutral will always be less than the hot wire and the GFCI will always trip, correct?

Sorry, I am just trying to get my basics right.



leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET

Regardless what potential you are using as your reference (neutral is often used as 0V reference in the context of line voltage AC) the voltage on hot and neutral will be different (by about 120V in a North American household).

Any current coming from the power source (utility, generator) through the hot wire to the load needs to somehow return to the power source to complete the circuit. The normal return path is the neutral wire which carries the exact same strength current in the opposite direction. In a ground fault situation a portion of the return current takes an alternate return path (ground wire, water pipe, moist soil, ...) which causes the current in the hot wire to be different from the current in the neutral wire. Even a slight difference in currents is sufficient for the GFCI to trip.
--
Got some spare cpu cycles ? Join Team Helix or Team Starfire!


garys_2k
Premium
join:2004-05-07
Farmington, MI
Reviews:
·Callcentric
·callwithus

1 recommendation

reply to iLearn

said by iLearn:

Thanks leibold and LazMan.

@ leibold - I wanted some clarification, you said 'differential in current between hot and neutral', do you mean differential in voltage instead? I am saying this because as far as I know, the neutral carries the different between the current coming in through hot and the amp (current) used by the resistance (a bulb for example). So the current flowing through the neutral will always be less than the hot wire and the GFCI will always trip, correct?

Sorry, I am just trying to get my basics right.

Think of voltage like the water pressure on a pipe system and current as the amount of water flow. The voltage (pressure) pushes the water (electricity) through the pipes (wires) but the flow (current) is the same no matter which of the series connected pipes (wires) you measured it.

Now, if the pipes should spring a leak, then the one supplying the water (electricity) will have more flow (current) than the one "downstream" (past) the leak. That leak will be bleeding off some of the flow (current) that was supposed to run through the pipe (wire). The flows (currents) in the pipe (wire) supplying the system won't balance with the flow (current) in the pipe (wire) carrying the flow (current) away.

In no case does the total pressure (voltage) really enter into it, that's what makes the flow (current) happen, but whether the leak is there, or not, the pressure (voltage) won't change much.

Does that help, or make it worse?

iLearn

join:2013-01-16
canada

Thank you. I understand it now.


lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1

Here is a diagram from wikipedia RCD entry and really simplified description to help you visualize what is inside a typical GFCI outlet.

Both hot and neutral (L/N) conductors pass through the core of a single current transformer (3). Ideally the currents flowing through L/N are identical and in opposite direction, so effectively zero current flows through the coil (2).

But when there is some leakage current from either L or N (to some grounded human or grounded object) the electromagnet (1) disconnects both L/N conductors from the outlet.

The ground conductor (when available) is connected straight through to the ground of the outlet. So when a GFCI outlet has tripped, ground prong is still connected to ground, but the L/N prongs are both floating.

P.S. The test switch (4) bypasses about 5mA from L to N.

iLearn

join:2013-01-16
canada

ah great, now I am confused again (j/k)


lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to iLearn

said by iLearn:

... do we need a ground wire to make an outlet GCFI protected? I have heard mixed opinions on this ...

The ground wire is not shown in the diagram because it is not "technically" required to "make an outlet GFCI protected" ... only the hot and neutral wires are disconnected by black magic which saves human lives.

Bob4
Account deleted

join:2012-07-22
New Jersey
Reviews:
·Optimum Online

1 recommendation

reply to iLearn

Shorter answer: With a properly-functioning appliance, the current on the hot and neutral prongs is the same. If there's a problem and the current is instead traveling through, for example, your body, the GFCI outlet will trip and cut-off the current. A ground wire is not necessary for this protection.


iLearn

join:2013-01-16
canada
reply to iLearn

Question:

I just noticed that my GFCI outlet in the bathroom upstairs tripped. That circuit feeds the 2nd bathroom and the powder room as well. That does happens once every few months.

My question is, is this because there is a short somewhere or it happens because there could be too much load on the circuit?

If it happens because of over loading then should it not trip the breaker in the panel instead?

Thanks



leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET

said by iLearn:

My question is, is this because there is a short somewhere or it happens because there could be too much load on the circuit?

It is guaranteed neither of those reasons. A short circuit (hot to neutral) or overload condition does not trip a GFCI (those conditions will trip a breaker which is an over-current protection device).

GFCI (ground fault circuit interrupter) will trip if there is a ground fault (some of the current from the hot wire does not return through the neutral wire creating an imbalance).
--
Got some spare cpu cycles ? Join Team Helix or Team Starfire!


LazMan
Premium
join:2003-03-26
canada

Could also be the GCFI showing it's age... They've been known to develop nuisance trips over time.

Is there anything specific plugged in or running when it trips? Any rhyme or reason, or is it random? Do you leave anything plugged in (toothbrush charger, razor, night-light, ???) all the time, that could be causing it?

If it's random, and there's nothing plugged in, I'd probably start with replacing the GFCI, myself.



cowboyro
Premium
join:2000-10-11
Shelton, CT
reply to iLearn

said by iLearn:

I just noticed that my GFCI outlet in the bathroom upstairs tripped. That circuit feeds the 2nd bathroom and the powder room as well. That does happens once every few months.

My question is, is this because there is a short somewhere or it happens because there could be too much load on the circuit?

It's not because of a short. GFCIs are notorious for false tripping. Simple noise on a circuit can cause one to trip. I can reliably trip a certain GFCI by switching on/off a fan [which is not downstream] few times and the GFCI of the hair drier by plugging/unplugging a shaver maybe 5-6 times in the same outlet.


leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET
reply to LazMan

GFCI are known to go bad, but not nearly at the rates many people think. When GFCI really fail the common failure modes are:
- not tripping in the presence of a fault current
- not being able to reset the GFCI after it tripped
Random trips as a result of a defect GFCI are rare.

In the majority of cases there is a real reason for the supposedly bogus "nuisance trip" such as humidity (often in conjunction with dust/dirt), defect appliances (especially motors/transformers where copper coils are only insulated with a thin coat of lacquer) or deteriorating wire insulation (either due to age or damaged by handyman or rodent).

Needless to say, bypassing or removing a GFCI because it keeps tripping creates a really dangerous situation since in the majority of cases the GFCI was alerting you to the presence of a real problem.

I don't like it when one GFCI is used to protect several locations since it makes locating the problem harder. My recommendation for a first step would be to install two more GFCI to protect each of the two bathrooms and the powder room separately. Troubleshooting will become easier once you know in which room to look for the problem.
--
Got some spare cpu cycles ? Join Team Helix or Team Starfire!


lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to iLearn

said by iLearn:

I just noticed that my GFCI outlet in the bathroom upstairs tripped. That circuit feeds the 2nd bathroom and the powder room as well.

Most probably that GFCI tripps because of too much capacitance (to ground) on the convoluted wiring. Separate circuits for each bathroom should fix that ... until you install bathroom heaters.


LazMan
Premium
join:2003-03-26
canada
reply to leibold

@liebold I agree fully - that's why I asked if anything was plugged in or in use when it tripped; or if it was truly random.

I also suggested REPLACING the GFCI, not removing it... It's there for a purpose; and it may be doing it's job. A new GFCI gives a known-good starting point, and if the trips continue, it's time to look deeper.

Without knowing how the OP's place is wired; hard to say how involved rewiring to have seperate GFCI's would be.



leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET

Yes, I realize nobody suggested simply removing the GFCI in this thread. It was just a free "Public Safety Announcement"

It is human nature to look for easy solutions and I have heard/read many times were someone chose to simply remove the GFCI outlet (or GFCI breaker) instead of trying to identify and fix the real problem.
--
Got some spare cpu cycles ? Join Team Helix or Team Starfire!



Thane_Bitter
Inquire within
Premium
join:2005-01-20
Reviews:
·Bell Sympatico
reply to iLearn

Is this a 60's house? Next time you are over take a look at the box the outlet fits into (shutting off the power first of course). Its possible that the box was grounded but that no ground wire was extended out to the actual device. With the outlet out of the way you should be able to see the wire as it feeds in and is clamped, and the coloured line and neutral wires, if you are lucky a bare copper wire will also emerge and run to a large screw at the back of the box.

If this is your situation a bare section of copper wire (of the appropriate gauge) can be added to connect between the outlet ground and the box ground.


garys_2k
Premium
join:2004-05-07
Farmington, MI
reply to iLearn

Or, if the box is steel and is grounded, just use self-grounding outlets.