Use of AFCI/GFCI breakers in Off-grid system

Hill_Country · September 2014

I'm wondering if folks can weigh in on their experience with AFCI or GFCI breakers (not receptacles, breakers) in an off-grid system on the AC side of things. I've seen combo AFCI/GFCI breakers available for sale, but am wondering if they are more trouble (nuisance tripping, etc.) than they're worth. Anyone care to share their real-world experience with these combo AFCI/GFCI breakers (or just AFCI breakers)?

I will have an off-grid system (no grid tie!) and will have a Magnum MS-4448PAE (120v/240v) inverter that will be connected to a standard AC panel (i.e. Load center), which feeds various home-run circuits throughout the house (no shared neutrals). Right now I have no 240volt circuits, but could in the future. Nothing more than 20 amp circuits in EMT conduit serving the various receptacles are planned for now. I'm debating whether to just use GFCI receptacles at the point of use, and not bother with AFCI/GFCI breakers at all. The county we live in does not require an electrical permit, so no AHJ will be reviewing the system. That being said, I would like to be as safe as possible and follow NEC guidelines where possible.

Your suggestions/comments are welcome!

BB. · September 2014

Re: Use of AFCI/GFCI breakers in Off-grid system

Arc Fault was to "protect" against somebody running an extension cord under the carpet in a bedroom --- Getting walked on, breaking or shorting, and the arc starting a fire.

If your home wiring is done to code--Arc faults are not very common (with the possible exception of home wiring done in the 1960's-1970's range with aluminum wiring).

http://inspectapedia.com/aluminum/Aluminum_Wiring.htm

Whether the Aluminum wiring failures would be helped with Arc Fault Breakers--I don't know--But in any case it is probably not an issue that you have with your home (I hope).

The complaint I have read most often is that brushed motors (universal motors) used in vacuum cleaners are a common cause of arc fault trips. And tend to tick people off.

For GFI--They do not appear to have significant issues with false tripping (unless the GFCI its self fails--Which does happen--Just replace and you are good to go).

For me--I prefer GFCI to be outlets near point of use (kitchen sinks, outdoors, bathrooms, etc.). That way, if you have a fault--It is pretty much isolated to the point of use and easy to debug/find the problem (or replace the bad GFCI outlet).

What I do not like, is to put a single GFI outlet or breaker on a branch circuit that has both outlets and lighting. In many off grid homes, the actual number of branch circuits is small (not much power is used from a single, small AC inverter), so it is possible to share a GFI Breaker between lighting (and/or ceiling lights) and outlets.

A ground fault not only turns off the offending load, it can kill the lighting in the home/cabin/RV and plunge you into darkness.

So--My two cents--Don't bother with Arc Fault breakers, and only install GFI breakers on dedicated circuits with outlets. If you have circuits that share outlets+lights, put in GFCI outlets in where needed (you can have one GFI outlet connected to several down stream outlets and be protected--There is an "INPUT" and an "OUTPUT" on the GFCI outlet so you can use one GFCI to protect several down stream outlets.

-Bill

vtmaps · September 2014

Re: Use of AFCI/GFCI breakers in Off-grid system

BB. wrote: »

For me--I prefer GFCI to be outlets near point of use (kitchen sinks, outdoors, bathrooms, etc.). That way, if you have a fault--It is pretty much isolated to the point of use and easy to debug/find the problem (or replace the bad GFCI outlet).

I have never had to debug/find the problem... It seems that a couple of times a year the GFCI receptacle just trips for no obvious reason, often when no one's home. Be certain that all GFCI outlets are conveniently located... not behind the refrigerator, for example. (Speaking of which, do not put the fridge on a GFCI outlet... you may come home to a warm fridge). Some GFCIs come with a little green LED that is lit when the receptacle is powered, others come with a little red LED that is lit when the GFCI trips.... either way, locate the receptacles so that you can easily see the lights when you walk in the room.

BB. wrote: »

(you can have one GFI outlet connected to several down stream outlets and be protected--There is an "INPUT" and an "OUTPUT" on the GFCI outlet so you can use one GFCI to protect several down stream outlets.

I'm not sure why GFCIs seem to nuisance trip on occasion... I think that the larger the circuit that the GFCI protects, the more likely it is to nuisance trip. This is an argument against GFCI breakers. In my opinion, a GFCI receptacle should only protect one or two nearby downstream receptacles.

--vtMaps

Hill_Country · September 2014

Re: Use of AFCI/GFCI breakers in Off-grid system

Thanks y'all! Because we are off-grid, we won't be using a vacuum cleaner at all (we'll only have concrete floors, no carpet!), so that won't be a problem.

Sounds like the preferred route is to go with GFCI receptacles (aka "outlets") at the point of use and not bother with AFCI/GFCI breakers. It's tough because the NEC 2014 calls for AFCI on many of the non-GFCI rooms (i.e. family areas, bedrooms, etc.), so it's tough to see a requirement like that for AFCI protection that does not lend itself to real-world practicality.

I appreciate your help on this, thanks!

BB. · September 2014

Re: Use of AFCI/GFCI breakers in Off-grid system

I guess "they are worried about fires where people may sleep... An alternative would be to ensure you have working smoke alarms in these areas.

-Bill

PS: I keep misspelling "receptacles" as "recepticals" (browser spell check does not even auto correct this bad of misspelling), so I use "outlets" instead.

Dave Angelini · September 2014

Re: Use of AFCI/GFCI breakers in Off-grid system

Not to worry about the lack of a vacuum cleaner, you can still trip the GFCI with a good blender and thirsty guests. If you can stay away from AFCI, you will not be powering the beasts! You can feel the heat they give off, even in summer! Maybe they build better AFCI than I have seen? Good Luck

Hill_Country wrote: »

Thanks y'all! Because we are off-grid, we won't be using a vacuum cleaner at all (we'll only have concrete floors, no carpet!), so that won't be a problem.

Sounds like the preferred route is to go with GFCI receptacles (aka "outlets") at the point of use and not bother with AFCI/GFCI breakers. It's tough because the NEC 2014 calls for AFCI on many of the non-GFCI rooms (i.e. family areas, bedrooms, etc.), so it's tough to see a requirement like that for AFCI protection that does not lend itself to real-world practicality.

I appreciate your help on this, thanks!

Hill_Country · September 2014

Re: Use of AFCI/GFCI breakers in Off-grid system

vtmaps wrote: »

..Some GFCIs come with a little green LED that is lit when the receptacle is powered, others come with a little red LED that is lit when the GFCI trips....--vtMaps

I've wondered about this with GFCI outlets...in an off-grid situation in which the inverter is sometimes "searching" (i.e. in my case the Magnum inverter is configured such that it will take a minimum AC load of 5 watts to wake the inverter), do the green LED's act as a phantom load at all? Or, a better question, do the green LED's on the GFCI outlets just do not come on until there is a sufficient load to wake the inverter? And does this cause any issues with these GFCI outlets at all in a setting where the inverter will be "searching"?

Mountain Don · September 2014

Re: Use of AFCI/GFCI breakers in Off-grid system

With the search function on our VFX Outback the green LED's on the GFCI would blink in time with the search function pulses. Ours was fine tuned to power up with as little power demand as an LED night light. Never had any miscues or failures until the lightning struck.

BB. · September 2014

Re: Use of AFCI/GFCI breakers in Off-grid system

Just to give the other side of the story:

The U.S. Consumer Product Safety Commission (CPSC) estimates that Combination Arc Fault Circuit Interrupters could prevent more than 50 percent of the electrical fires that occur every year. Square D™ QO Combination Arc Fault Circuit Interrupters (AFCIs) are the first commercially available circuit breaker designed to meet the National Electrical Code® (NEC®) requirements for Combination AFCI protection. Combination AFCI’s, also known as Combination Arc Fault (CAFI) Circuit Breakers sense and respond to a broader range of arcing incidents than the standard AFCI circuit breakers, providing enhanced protection against electrical fires for homes and families.

Series arcing is often associated with damaged devices or cord sets. A series arc is an arcing incident across a break in a conductor. A common example is a cut across one of the two wires in a lamp cord, with a dangerous arc forming in the gap.

The CAFI Circuit Breaker detects the arcing condition and turns off or trips the circuit, thus providing the enhanced electrical safety and protection. Square D Combination Arc Fault Circuit Breakers are UL® listed, available in QO® and HomeLine™ 1-Pole and 2-Pole circuit breakers with 15 and 20 ampere ratings.

-Bill

westbranch · September 2014

Re: Use of AFCI/GFCI breakers in Off-grid system

Sounds to me like no one should use a gift of an old fashioned lamp or whatever from grandma's house before replacing the internal wiring and switch....

Also a problem for slum landlords...

Hill_Country · May 2015

Wanted to provide an update for those that may be reading this post...we pretty much have our electrical system (DC and AC) ready to go. I just need to finish wiring the outlets and installing some smaller EMT conduit runs. On the AC side of things I have chosen to go with the GFCI outlets where GFCI is necessary (bathroom, outdoor, etc.) as per NEC.

new2PV · June 2015

Attachment not found.

NEC requires ARC fault DC breakers for PV arrays over 80 volts, I would be more worried on the DC side than the AC side of things. Strange the sponser of this site does not sell them online and they are a code requirement for all installations. So you may want to look into that also..

mike95490 · June 2015

...NEC requires ARC fault DC breakers for PV arrays over 80 volts, I would be more worried on the DC side than the AC side of things. Strange the sponser of this site does not sell them online and they are a code requirement for all installations. So you may want to look into that also..

Not all areas have adopted the latest code

BB. · June 2015

Hmm... It depends on what NEC means by Arc Fault breakers... NAWS does sell ground fault breakers which were an early attempt at addressing arc fault issues:

Ground Fault Protection Circuit Breakers

Personally, I think DC GFI Breaker and the "current sense" circuit (generally a fuse or small breaker between earth ground and return/negative ground lead of the solar power system) is dangerous as defined by the NEC.

There are true Arc Fault breakers and systems. The Classic MPPT Solar Charge Controller does have an Arc Fault detection circuit to protect against solar array arc faults.

And MorningStar has a standalone DC Arc Fault standalone breaker setup:

http://www.morningstarcorp.com/products/ground-fault-protection-device/

-Bill

new2PV · June 2015

That morningstar unit looks good, but that is it actually listed as an Arc fault device I'm not sure. Also my Schneider mppt-60-150 has a built in GFI also, and i think it will give visual indication when tripped on the led display. Do you think that the Schneider buit in PVFG is a dangerous design? It has a 1 amp 600v fuse to ground, also you can;t ground the battery dc- anywhere else in the system. These devices look pretty good for arc fault detection but they need an external source and external trip relay. These came out in 2013 so they should be available.
http://www.sensata.com/uses/solar.htm

zoneblue · June 2015

BB. wrote: »

For me--I prefer GFCI to be outlets near point of use (kitchen sinks, outdoors, bathrooms, etc.). That way, if you have a fault--It is pretty much isolated to the point of use and easy to debug/find the problem (or replace the bad GFCI outlet).

In NZ RCDs (GFCI) are now required on all branch circuits, with some minor exceptions, (dedicated heavy loads like commercial driers). The code does make mention of the desirability of avoiding situations where a RCD popping cuts all lighting, as a safety issue. But thats generally taken care of by splitting lighting into more than one circuit and using seperate RCDs.

Personally, ive gone with a single house wide RCD. Make sure you buy a top quality brand. And, here our lighting is all DC. Thats becasue the inverter is off overnight and at other times such as bad weather events. (People tend to underestimate the burdon that inverter tare is on small to medium systems.)

vtmaps · June 2015

new2PV wrote: »

Do you think that the Schneider buit in PVFG is a dangerous design? It has a 1 amp 600v fuse to ground, also you can;t ground the battery dc- anywhere else in the system.

The reason you cannot ground your DC system anywhere else is because the 1 amp fuse is the bond to ground (there must be only one bond). Therefore it is dangerous because when the fuse blows there is no bond at all.

Disclaimer: I am not familiar with the Schneider design... I base my conclusion on my knowledge of similar designs that use a 1 amp fuse and permit no other bonding.

--vtMaps

new2PV · June 2015

I will ask Schneider about that..but it seems to make sense what your saying..

new2PV · June 2015

I have asked Schneider if there design leave the PV array ungrounded in the event of a Ground fault. They have not answered the question, they just explained not to bond the ground anywhere else. I Don;t know if I should use this built GF fuse or go with the morningstar PVGFI. Opinions?

jet1200 · July 2015

I have the Midnite Classic 200, a Samlex 2000 watt pure sine wave inverter and a Reliance Controls transfer switch. The inverter has a terminal block labeled (L AC) on one side and (N OUTPUT) on the other side. The transfer switch has 3 input lines, a red a black and a neutral. It has 2 watt meters, I expect that switch is divided to distribute the loads from a generator. I took the N OUTPUT from the inverter and tied it to the whit wire of the transfer switch. this continues on out to the mains panel neutral. I took the L AC from the inverter and tied it to both the red and black wires in the transfer switch. there is also a ground wire running from the transfer switch to the mains panel. The transfer switch is a 10 position switch.
All seems to be working OK, except one line that is attached to an EATON arc fault circuit interrupter breaker, breaks instantaneously. There appears to be a problem with the neutral connections. I removed the neutral between the Mains panel and the transfer switch and it doesn't break, but I think the voltage was about 80 volts.

Can anyone help me solve this problem?

Use of AFCI/GFCI breakers in Off-grid system

Comments

Categories