GFCI operation question

Only requirement I'm aware of where GFPE's (30 ma GFCI) are required in the

2005 NEC is Section 426.28.
Reply to
PPS
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What is an AFIC?

Thanks!

David

Reply to
David Combs
[snip]

An Arc Fault Interrupted Circuit. A circuit that has no current in it because you didn't use an AFCI, your house was on fire, and the fire department cut off the power.

Reply to
Sam E

Arc Fault Circuit Interrupter. The AFCI breakers look like, and wire like GFCIs. AFCIs trip on arcs. The NEC requires them on new circuits to bedrooms. The proposed 2008 NEC requires them for all residential 15 and

20A circuits IIRC (could still be changed though).

A good paper from the Consumer Product Safety Commission on AFCIs is at

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explains the rationalle for using AFCIs describes how they work.

bud--

Reply to
Bud--

| Arc Fault Circuit Interrupter. The AFCI breakers look like, and wire | like GFCIs. AFCIs trip on arcs. The NEC requires them on new circuits to | bedrooms. The proposed 2008 NEC requires them for all residential 15 and | 20A circuits IIRC (could still be changed though).

And AFCI-only device could be made to work without accessing the neutral of the circuit involved. The issue is the AFCI device needs to use power to function. Possibly that is the only purpose of the neutral pigtail if the device does not include any GFCI function.

I hope the change goes through. But I would like to see local AHJ rules that permit case-by-case exceptions to be made where AFCI devices are found to be incompatible with certain appliances.

And regarding the issue of putting smoke detectors on AFCI protected circuits. The simple solution is keep receptacle circuits and lighting circuits separate, and put the smoke detectors on the lighting circuits. Those circuits should have much less instance of nuisance trips, and would more readily be noticed if they are opened, in case the smoke detector false to alarm.

Reply to
phil-news-nospam

We had to have smoke detectors on a separate dedicated circuit. Our contractor decided not to sub out the electrical work, and sure looked upset when he learned he had to rewire four levels of smoke detectors.

S
Reply to
mrsgator88

But all AFCIs include a 30mA GFCI as part of the protection. (That is not the same as a 6mA GFCI for shock protection of people.)

Just to be clear, lighting circuits that include bedrooms have to be on an AFCI. (I think that is what you said.)

bud--

Reply to
Bud--

In alt.engineering.electrical Bud-- wrote: | snipped-for-privacy@ipal.net wrote: |> In alt.engineering.electrical Bud-- wrote: |> |> | Arc Fault Circuit Interrupter. The AFCI breakers look like, and wire |> | like GFCIs. AFCIs trip on arcs. The NEC requires them on new circuits to |> | bedrooms. The proposed 2008 NEC requires them for all residential 15 and |> | 20A circuits IIRC (could still be changed though). |> |> And AFCI-only device could be made to work without accessing the neutral |> of the circuit involved. The issue is the AFCI device needs to use power |> to function. Possibly that is the only purpose of the neutral pigtail if |> the device does not include any GFCI function. |> | | But all AFCIs include a 30mA GFCI as part of the protection. (That is | not the same as a 6mA GFCI for shock protection of people.)

I've seen some that don't. Those were from Cutler-Hammer, the company that makes AFCI without GFCI, AFCI with 30maGFCI, and AFCI with 6maGFCI.

If the NEC ends up requiring the GFCI function, then the ones without GFCI would likely end up being no longer made. But right not it is not clear what the NEC requires NOW (2005 code) or will require (2008 code). All we know is that the scope of where AFCI is required appears to be expanding.

|> And regarding the issue of putting smoke detectors on AFCI protected |> circuits. The simple solution is keep receptacle circuits and lighting |> circuits separate, and put the smoke detectors on the lighting circuits. |> Those circuits should have much less instance of nuisance trips, and |> would more readily be noticed if they are opened, in case the smoke |> detector false to alarm. |> | | Just to be clear, lighting circuits that include bedrooms have to be on | an AFCI. (I think that is what you said.)

All the circuits supplying outlets in the bedrooms must be AFCI protected.

The issue with smoke detectors is more complex. I do believe they must be on AFCI, and I think that is appropriate. I do not expect the smoke detectors to be any source of nuisance trips. Thus it might seem to be a good plan to put them all on their own circuit. But I don't trust that they will alarm when the power is lost. The reason is because that would cause problems in utility outages. Do you want all your smoke detectors beeping when a storm knocks out your power? But what if the branch circuit the smoke detectors are on loses power. You might not even notice that a problem exists. Connecting smoke detectors with receptacles is a bad idea becauseof two reasons. Either the receptacle might not even get used, or the receptacle's usage might be the source of excess nuisance trips. That could compromise the safety of the smoke detectors. My idea is to put them on the same circuit as regularly used overhead lights, such as hall lights or stairway lights. That way, if there is a circuit trip that does affect the smoke detectors, you will be alerted to a problem with that breaker, and motivated to correct it.

Reply to
phil-news-nospam

Smoke detectors that are designed to be interconnected will usually have a backup battery and will chirp every so often if power is lost.

Reply to
Thomas D. Horne, FF EMT

Have a reference handy for AFCIs without 30mA ground fault detection?

(There was a proposal for the 2008 NEC to require that but it was rejected.)

Do they chirp if the battery is dead? Removed? I havn't played with them.

The way I understand the 2008 NEC-ROP, NFPA 760 requires smoke detectors that are on AFCI circuits have a secondary power source (battery). Another hidden requirement.

IMHO requiring smoke detectors to be on an AFCI circuit lowers overall fire safety and is dumb.

bud--

Reply to
Bud--

| Have a reference handy for AFCIs without 30mA ground fault detection?

Some have 5ma GFCI and some have no GFCI:

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Pages 3 and 4:
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| The way I understand the 2008 NEC-ROP, NFPA 760 requires smoke detectors | that are on AFCI circuits have a secondary power source (battery). | Another hidden requirement. | | IMHO requiring smoke detectors to be on an AFCI circuit lowers overall | fire safety and is dumb.

I'm not convinced of that, yet.

Reply to
phil-news-nospam

Those without GFCI protection are intended for use in habitable and non-habitable spaces not requiring ground fault protection (living rooms and the like.)

Those with 5ma GFCI protection are intended to serve bathrooms, kitchens and anywhere where a standard GFCI is required.

Those with 30ma GFCI is designed to serve residential equipment noted in the NEC requiring 30 ma GFCI (actually termed GFEP to differentiate between the two.) Article 426.28 only requires ground fault protection for equipment, no personnel and that's to only place it can be used to meet code. To protect personnel, you must use 5ma protection.

Reply to
PPS

| Those without GFCI protection are intended for use in habitable and | non-habitable spaces not requiring ground fault protection (living rooms and | the like.) | | Those with 5ma GFCI protection are intended to serve bathrooms, kitchens and | anywhere where a standard GFCI is required. | | Those with 30ma GFCI is designed to serve residential equipment noted in the | NEC requiring 30 ma GFCI (actually termed GFEP to differentiate between the | two.) Article 426.28 only requires ground fault protection for equipment, no | personnel and that's to only place it can be used to meet code. To protect | personnel, you must use 5ma protection.

This is along the lines of what I expected, and certainly sounds very reasonable. Still, the required ground fault protection can be had with an AFCI that has no GFCI, or only has 30ma GFCI, as long as the 5ma GFCI receptacles are also used, where the GFCI people protection is required. Whether one would want to do it that way is another matter.

In a bathroom, there is an advantage to having the ability to reset the GFCI device right there. That advantage may or may not be relevant for a kitchen. Other areas like a garage are probably not much of a concern.

I have been told, but have never sacrificed a device to verify, or set up the appropriate test, that GFCI receptacles open BOTH the hot wire AND the neutral wire when they trip. If so, why is that? Is it to offer at least some protection even when the device is miswired? Or is there even some risk with voltages on the neutral wire?

I do believe some neutral wire risk exists. It's certainly not as much as for the hot wire, usually in terms of voltage, and in terms of exposure events. One example of when the risk is high is when there is a open in in the supply neutral. But the chance of that happening coincident with contacting the neutral to ground, is much lower than either alone. The other risk is the voltage present as a function of the voltage drop along the supply neutral from the point of bonding to the point of contact. That's generally a very low voltage, though it can vary with loading on the system. Still, I'd feel safer having an interruption mechanism that will open BOTH wires together when tripped.

Suppose you have an AFCI that includes GFCI protection, either at the 5ma level or the 30ma level, followed by a GFCI receptacle. Leakage from the neutral to ground would still result in a trip. But can it be guaranteed that the receptacle device will always open? Perhaps the breaker will open first, and de-energize the circuit before the receptacle can open, leaving the neutral wire still connected. To be assured that the receptacle will trip, I'd have to have no GFCI in the breaker, and place the GFCI protection in the receptacle, assuming it is designed to open the neutral.

If I am forced to put GFCI protection in the breaker along with the AFCI protection, or if GFCI receptacles don't actually have neutral contacts that can be opened, I do have a fallback plan. I would run the circuit through a secondary box containing a 2-pole normally open electrically closed contactor. The circuit would run through these contacts. The coil would be powered from the supply side. If the breaker opens the hot wire, the coil will de-energize and open both wires. It won't be as quick an open since such contactors aren't listed for GFCI protection. But at least it will be something that can prevent certain problems. For shared neutral circuits, this would be a 3-pole contactor with a 240 volt coil. These are avalable from Square-D and Cutler-Hammer. One issue that some people might be concerned with is the constant power used by the coil, 24x365xN.

Reply to
phil-news-nospam

30mA ground fault detection in an AFCI is for arc protection. Far as I know all AFCIs include it (though I need to look harder at phil's 2nd link). Arcs can produce carbon paths which, if a ground is available, can produce ground fault currents. That may produce a trip before there is an arc or before an arc is detected.

In the Consumer Product Safety Commission paper at:

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is explained on pdf page 14.

Phil has a link in another thread to:

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is a UL investigation showing that a "glowing connection" at a receptacle binding screw may (or may not) cause an AFCI trip through the 30mA ground fault function.

I have read in newsgroups (so it must be true) that both poles are opened for hot-neutral-reverse protection.

GFCIs (5mA) are now required to not work with reverse load-line terminal wiring. (Previously the load terminals connected to the receptacle.) I don't think you can do that without double pole contacts line-receptacle and line-load. And I don't think it can be done without that being a NO contact that requires the device to be powered to connect (which it wouldn't be if the line-side neutral was open).

In both cases testing can be easily done without a hammer but so far I have been too lazy.

bud--

Reply to
Bud--

Here's a good place to learn more.

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Reply to
PPS
[snip]

Even when that's exactly what you want.

[snip]
Reply to
Mark Lloyd

Just opens the ungrounded conductor, not the ground (mistakenly called a neutral). It uses a special transformer to measure the current on the grounded and ungounded lines, and if they are not the same (within 5ma) it trips; assums that the lost current is leaking to ground somewhere (possibly through a person).

Although the grounded conductor carries the same current as the ungrounded (white or identified) conductor (a white wire is only a neutral in a 120/240 volt circuit, and carrys the unblanced load of the 120/240 volt applaince), it's at the same potential as you are. Both are grounded to the earth and (hopefully) there is no potential difference when a person contacts the white wire; threrefor no shock hazzard (under normal conditions, IE wired properly in the first place.)

Reply to
PPS

In alt.engineering.electrical PPS wrote: | |> 30mA ground fault detection in an AFCI is for arc protection. Far as I |> know all AFCIs include it (though I need to look harder at phil's 2nd |> link). | | Here's a good place to learn more. |

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Sounds like we are now back to the beginning.

Reply to
phil-news-nospam

In alt.engineering.electrical PPS wrote: | |> I have been told, but have never sacrificed a device to verify, or set up |> the appropriate test, that GFCI receptacles open BOTH the hot wire AND the |> neutral wire when they trip. If so, why is that? Is it to offer at least |> some protection even when the device is miswired? Or is there even some |> risk with voltages on the neutral wire? | | Just opens the ungrounded conductor, not the ground (mistakenly called a | neutral). It uses a special transformer to measure the current on the | grounded and ungounded lines, and if they are not the same (within 5ma) it | trips; assums that the lost current is leaking to ground somewhere (possibly | through a person).

So you are the first to contradict the others and say this?

I know how they work. The issue is whether the groundED conductor, commonly known as the neutral, is opened as well.

|> I do believe some neutral wire risk exists. It's certainly not as much as | | Although the grounded conductor carries the same current as the ungrounded | (white or identified) conductor (a white wire is only a neutral in a 120/240 | volt circuit, and carrys the unblanced load of the 120/240 volt applaince), | it's at the same potential as you are. Both are grounded to the earth and | (hopefully) there is no potential difference when a person contacts the | white wire; threrefor no shock hazzard (under normal conditions, IE wired | properly in the first place.)

Not quite true. The neutral (I don't know why you are caling it ungrounded) is NOT at exactly the same potential as ground. If it were, we'd have never had to have a separate groundING/EGC wire. The fact is, the neutral CAN be at potentials above the earth for various reasons. In most cases it will be just a few volts or a fraction of a volt due to voltage drop. In fault cases, it can be more serious. In open neutral cases it can be very serious.

Reply to
phil-news-nospam

When the supply wires are connected to the LOAD terminals on old GFCIs, the GFCI receptacle is not protected - it is live even if the GFCI is tripped. (I believe the downstream circuit, which would be connected to the LINE terminals, is protected.)

Under the new UL standard, which I think was adopted about 2 years ago, if you connect supply wires to the LOAD terminals the GFCI receptacle and LOAD terminals will always be dead.

I may have tried to say that with too few words.

bud--

Reply to
Bud--

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