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mysterylectric 05-11-2011 08:31 PM

Now, Square D Combo AFCI Breaker Trips Opens w/No Load Side Connections QO120CAFI

I have a Square D QO120CAFI issue DP-3640 combination AFCI circuit breaker. Basically I bought it to see for myself if these functioned as advertised. It is in a subpanel that supplies the kitchen.

It seemed just fine for about a month, maybe two.

Then it tripped one day. I don't think it was precipitated by an obvious event on the circuit. On the other hand, I think I was in the kitchen (w/the panel) at the time it happened, probably using one or more appliances and perhaps unplugging/plugging something in.

A persistent fault seemed unlikely so I reset the breaker. It popped open right away.

Unplugged all appliances from circuit, still popped.

Shut off breakers to all other kitchen loads. Ditto

I probably disconnected the load side hot wire first. Still popped upon reset.

Then I probably disconnected load side neutral. Still popped.

Tossed the breaker aside for further investigation.

Today I put the breaker back into the panel and tied it to the neutral bar. Still trips, with no load side connections.

It won't trip with the breaker's neutral disconnected, of course.

I've read about the importance of making sure to reset these properly, ie: with gusto. No help.

It seems very unlikely to me that it is "nuisance tripping" in the traditional sense, ie: that the simple fact that there are no load side connections is causing a nuisance trip

It's probably about %80 certain I energized it without any load side connections when I first installed it, it never tripped during or after installation, except on hitting the test button.

So this breaker either suffered infant mortality or was destroyed by a common fault.

How common is this experience?

And, what's the fastest way to get a replacement from Schneider? Assuming things don't work out with the retailer (though I tend to think they will exchange it no questions asked).


kbsparky 05-11-2011 10:20 PM

Bad breaker. Take it back to the store, and ask for a replacement.

This type of thing happens all the time, and across all brands.

This is one reason why I do not believe that AFCI breakers are ready for prime time: They have been added into the Code as a result of extensive lobbying efforts from the manufacturers. The public has become the guinea pigs and beta testers of these.

Leah Frances 05-11-2011 10:22 PM

I've had one of these bad out of the box. Took it back, next one worked.

mysterylectric 05-11-2011 10:55 PM

Are these types of problems far more common with CAFI breakers? Far more even than for GFI? In theory I can see how a GFI could use as few as zero semiconductor components, at most some analog. CAFI's I's think really need microprocessors.

Yeah, from the beginning I saw this as a very difficult engineering task and noticed far more talk about why it's such a wonderful idea than talk about reliability or whether they currently work as intended. I bet a lot of homeowners will be replacing these themselves, with exact replacements or the standard equivalent. That's a lot of untrained fingers in a lot of boxes across the country.

frenchelectrican 05-12-2011 01:37 AM

I do know for the fact with early series of AFCI breakers they were kinda major pain in the back end and I have ran into that more than once when I did the service call.

Basically what I do is do a basic troubleshooting to make sure the neutal is not touching the ground conductor after that I go next step is get a GFCI breaker to test fire it to see if that hold if the GFCI breaker trip then you have grounding issue but if hold then I will dig deeper to find out the curpit.

For our Europeans side we do not have AFCI at all for now but not too far in future we will get something simauir what the North Américians have now.


jerryk1234 11-02-2011 09:55 AM

My new house ( built in 2008 ) has FOUR of these @#$@#$ things. They trip randomly. Sometimes, all four of them trip. Often when nobody's at home. It's a Square-D panel, I don't know the exact model# of the AFCI's.

My computers do NOT like having their power suddenly removed. OK, I put them on UPSs. OTOH, I do NOT like being woken up in the middle of the night by beeping UPS's.

Have AFCI's gotten any better in the four years since my house was built?

- JerryK

Billy_Bob 11-02-2011 10:57 AM

I recently read that radio frequencies from "Smart Electric Meters" can trip AFCI's!

Possible explanation to all these false trips? Maybe other RF too?

Here is a bit on that...

jerryk1234 11-02-2011 12:11 PM


Originally Posted by Billy_Bob (Post 762227)
I recently read that radio frequencies from "Smart Electric Meters" can trip AFCI's!

**** Ouch! That could indeed explain it. The combo AFCIs are quite complex, and probably have a microprocessor. If I buy a new one to try out, I might tear the old one apart, just for yuks.

- JerryK

kbsparky 11-02-2011 08:15 PM

Your surge units can trip out AFCI and GFCI devices by doing what they were designed to do.

Too bad the Code does not allow exceptions for such things these days ... :furious:

mc5w 10-23-2013 04:40 PM

Nuisance Tripping of AFCIs and GFCIs
There are a number of causes of nuisance tripping of AFCIs that involve the equipment ground fault protection circuit that trips at about 50 milliamperes leakage current, about 10 times where an American GFCI trips and about twice the 22.1 to 29.9 mA trip level of a British or European GFCI for people protection such as the Merlin Gerin 16201 resdiual current circuit breaker.

( UL recently admitted that the 22.1 to 29.9 mA trip level of a British or European IEC standard 61008 or 61009 GFCI is people protective when UL allowed electric vehicle chargers to use the 19 to 21 milliampere leakage current trip level for people protection. )

The purpose of using 50 mA equipment ground fault protection in an AFCI is so that if the romex contains an equipment ground the AFCI has a chance of picking up an insulation leak BEFORE it progresses to an arcing fault thus acting as an arc fault preventer.

1. If the neutral is accidentally regrounded this will cause a GFCI or AFCI to nuisance trip because of current diversion that registers as a ground fault.

2. I one time in the Spring of 2002 had to run cable from the basement to the attic to correct the matter that the front hallway chandelier was wired using a hot wire on the first floor and a neutral wire on nthe second floor. This was in a house that was built in the late 1970s or early 1980s. Every time they turned on the front hallway chandelier it would trip the equipment ground fault protection in the AFCI whose neutral had been tapped to avoid wiring the 3-way and 4-way switches with 14/3 WG romex.

3. According to SquareD the residual current transformer in an AFCI or GFCI can develop a nonlinear defect that causes nuisnace tripping when a motor starts or stops. Replacing the device fixes the problem.

4. When a single phase motor is starting or when any motor is stopping winding inductance can force a phantom ground fault to flow through insulation capacitance to ground, what is known as a 2nd order transient response. This can nuisance trip an AFCI or GFCI.

I have used Leviton's High Current GFCI to monitor a 3 HP motor and tank heater that were running on 277Y480 volt 3-phase. The High Current GFCI is compatible with 125 to 135 volt industrial control power.

5. Static electricity from the human body can also nuisance trip the ground fault protection in an AFCI or GFCI. UL allows people protection GFCIs to use an inverse time delay that amount to 1 second at 20 milliamperes and about 99 millisends at 99 milliamperes.

However, Leviton and Pass & Seymour have opted for a straight instantaneous trip for GFCIs that picks up on the first pulse of fault current and disconnects power in 1.5 to 3 cycles ( 25 to 50 milliseconds on 60 cycle power ).

jerryk1234 10-23-2013 05:51 PM

[QUOTE=mc5w;1257231]There are a number of causes of nuisance tripping of AFCIs that involve the equipment ground fault protection circuit that trips at about 50 milliamperes leakage current,

*** Maybe 50 MICROamperes? 50mA is an ENORMOUS current. Almost 6 watts at 110VAC.

The problem actually was a software bug. Square D had a published recall on these particular breakers, with date codes including mine. I replaced them all, and the problem went away. The software bug caused nuisance trips every 6 days, regardless of load or lack of load.

- Jerryk1234

mc5w 10-26-2013 04:14 PM

Ground Protection in AFCIs
International Electrotechnical Commission has shown that is it takes an equipment ground fault that is more than 300 milliampere to cause a fire on 240Y415 volts. This amounts to 72 watts generated by the electricity leak.

Hence, IEC standards 61008 and 61009 specify residual current circuits breakers for feeder protection in wood frame buildings can have a trip setting of 221 to 299 milliamperes and still be considered as substantially reducing the fire risk from an insulation leak in a feeder cable.

There are 3 other ground faulttrip settings that are considered to be fire protective by IEC which are 10 milliamperes, 22.1 to 29.9 mA, and no more that 99 mA for the next level up.

The 50 mA ground fault trip level was selected for American AFCIs as a level that provides good arc fault PREVENTION and at the same time will tolerated phantom ground fault from motors starting or stopping.

mc5w 10-26-2013 04:26 PM

Nuisance Tripping of 15 amp AFCIs
One of the other causes of nuisance tripping of 15 amp AFCIs is that 15 amp circuit breakers overload too easily, I have talked with electrical inspectors for Columbus, Ohio and Reynoldsburg, Ohio and they agree that a 15 amp circuit is technically illegal for supply of a 15 amp straight blade receptacle because Underwriters Laboratories allows portable appliances to pull 12.5 amperes through a 15 amp plug. Since we are only allowed to put 12 amps of load on a 15 amp circuit breaker because the rating goes down when placed in a box or panelboard, this is a problem. Among the loads that pull 12.5 amps through a 15 amp plug are portable heaters, flatirons, toaster ovens, and my Soleus LX-140 tabletop room air conditioner that uses 2 5 inch air hoses going out the window.

Electrical Testing Laboratories also allows 13 amps through a 15 amp plug. There are also vacuum cleaners which are advertised as having a 12-amp motor which means that there is nothing left for lighting or other loads.

Since 2011 NEC requires switch loops including 3-way and 4-way switches to accomodate timer switches and motion sensing switches that need to neutral the circuit can also accomodate vacuum cleaner receptacles. since we may need an extra box gang to accomodate the extra wires, a vacuum cleaner receptacle ( with or without night light ) is easier than special ordering a 2-gang plate with 1 side blank.

About half the cities in Ohio have realized these issues and have explicitly outlawed 15 amp wiring. Ohio Board of Building Standards has upheld the "no 15-amp wiring" rules because of the beforementioned Code conflicts and because the consumer gets more value from 20-amp wiring.

The complaints about 15-amp wiring that I get are:

"The circuit breakers are set kinda low."

"I have to use a heavy extension cord to plug my power saw into a kitchen outlet."


Best bet for supply of existing 15 amp wiring is to use a 20 amp combination AFCI breaker and then use a 15 amp breaker or fuse downstream. Steel City makes OWSWGEAR-25L devices for attaching old work ears to 4x4 boxes to accomodate a Bussmann 4x4 fusible cover with 2 switches and 2 15 amp type S fuses. With a little drilling and tapping the OWSWGEAR-25L can be used for SquareD's itty bitty 2 solt 30-amp circuit breaker boxes.

This way, when you do some heavy remodeling to upgrade the circuit cable to 20 amps you will not be using a 15 amp AFCI to supply 20-amp wiring particularly in this cities that have outlawed 15 amp wiring. You can also do the same thing with partitioning 15-amp circuit into 2, 3, or 4 pieces for load relief. Just install a few 20-amp T-slot child resistant receptacles ahead of the 15amp breaker.

Bussmann also makes a 15-amp class G fuse model SEC-15 that has comparable time delay to a 15 amp dual element type S fuse and they also make a panel mounted fuseholder for it.

CAUTION: 15-amp type S or type G fuses need to be 5.5 feet to 6.5 feet from the floor.

mc5w 10-26-2013 04:41 PM

AFCI Receptacles
2014 National Electrical Code will permit AFCI receptacles on romex with several restrictions:

1. The AFCI receptacle has to be installed at the first box downstream of the circuit breaker NEC 210.12(A)(2)b. There cannot be any splices between the breaker and the AFCI receptacle.

2. The 15 amp circuit breaker MUST have an instantaneous trip that does not exceed 300 amperes. NEC 210.12(A)(2)a. This means that Federal Pacific, Wadsworth, Zinsco, and ITE Pushmatic circuit breakers MUST COME OUT. There is also a federal court ruling Manoma Realty Management versus Federal Pacific Electric that says that there is no such thing as a Federal Pacific Circuit breaker that works. The same court ruling also says that ALL FPE circuit breakers made prior to 1980 will allow a short circuit to turn into a grenade or roman candle and set the building on fire.

After I replaced my parents' electrical sevice in December 1981 I dismantled some of the Pushmatic circuit breakers and some of them were thermal relay only ( outlawed ) and some of them had a magnetically actualed piston that allegedlu pushed on the thermal element during short circuits.

This past July 2013 I encountered 2 ITE Pushmatic panelboards where 7 of the circuit breakers were incapable of disconnecting power manually ot automatically. There equipment ground of the 2nd floor garbage disposer circuit had melted causing the metal switch box to register as hot and an electrocution hazard.

Also, the metal cased type XO circuit breakers for type MB panelboards that SquareD stopped making in 1959 are also infamous for acting like a fusebox that has pennies it which is why SquareD stopped making the XO circuit breakers.

3. The branch circuit length from the breaker to the AFCI receptacle cannot exceed 50 feet for #14 copper or 70 feet for #12 copper.

4. First box on circuit MUST be identified.

mc5w 10-27-2013 03:51 PM

AFCI and GFCI supposed to trip when supply neutral lost
I remembered last night that AFCIs and GFCIs are supposed to trip when the supply neutral is lost. This is because this condition disables the protective electronics and leaves the load side of the AFCI or GFCI hot.

This new requirement is because on a job site a GFCI lost its supply neutral and a result somebody got their rear end shocked off. UL revised its standards to cause a GFCI or AFCI to trip when it is running out of enough reserve power in the direct current filter capacitor to operate the shunt trip or to use an electrically held power relay.

This also means that you can no longer install a GFCI downstream of a control switch or power relay. The switch or power relay needs to be downstream of the GFCI or AFCI and separate switche receptacle installed. Fortunately, Magencraft makes a miniature power relay that can be crammed into the back of an extra deep box using extra extension rings.

Back in 2002 or 2003 I had to revise a rooftop GFCI receptacle that I installed back in 1992 that was originally switched by one of the poles of a 2-pole relay for switching the sign lights. The object was to allow installation of extra sign lighting. The revision was to install a continuously energized GFCI receptacle and then I installed an Omron G4B miniature power relay in the back of the box to control an adjacent switched receptacle.

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