I have a question about Ground Fault Circuit Interrupters.
These devices protect people who are unfortunate enough to touch a live wire.
A circuit breaker also works, but not quickly enough to avoid serious injury.
As I understand it, the best place, and logically the only place, to place one of these devices is at the head of the circuit. That is the outlet closest (electrically) to the service panel. That way if there is a short anyway on the line the entire circuit will be disabled. However, in talking to electricians recently, I find that building codes seem to require these devices anywhere there is an outlet near a source of water. The logic escapes me. The typical short for me is between me and neutral when I am working on an electrical fixture. That is why I am highly determined to make sure all circuits are off before I work on them. I get it right almost every time…
But I have never shorted a live wire to a water pipe or water. Certainly it could happen, and if there is a water leak, the water will short out wires, but nevertheless, I want full circuit protection.
So the simple solution is just load up the house with GFI boxes. Mildly expensive, but that isn’t a problem compared to burning down the house or killing myself.
However, and this finally is the question. I understand the GFI device not to work well if there is more than one such device on the circuit. As I understand it, each GFI works by testing the balance of current between hot and neutral. If suddenly a lot of current is coming down the hot wire-and not coming back the neutral, this is a bad thing and the circuit trips. But it accomplishes this measurement by trickling a very small amount of current to neutral. If you have too many GFIs in the circuit, the total current leakage is sufficient to make the GFI very sensitive to momentary surges and variations. Which causes a lot of false trips. So, the proper use of a GFI is to place it at the head of the circuit and it is not a good thing to put multiple GFIs on the circuit.
Can anyone confirm this description or explain how a GFI really works?
No. GFCIs work by passing the hot and neutral through a differential transformer. If the current through the hot equals the current through the neutral, the opposition cancels out (transformer designers say “bucks out”) and no voltage is induced on the secondary. Any imbalance between the hot and neutral current induces a proportional voltage in the secondary; if this imbalance exceeds 5 mA, the device trips the circuit off. This is very different from the operation of a circuit breaker, which is designed to trip in response to a current excess through the circuit. The two devices are NOT interchangeable. Each GFCI is allowed by the NEC to protect up to 6 downstream receptacles, switches or fixtures, and each protected device must carry a sticker which says “GFCI PROTECTED”. Putting GFCIs in areas without a potential path to ground through a human body is unnecessary.
The risk is not that the hot wire will be shorted by water, but rather you will be shorted to either hot or neutral and touch/grab a faucet, or water stream.
Without a GFI you could conduct a fatal amount of current across you heart.
My mother almost died this way back in the mid fifties. She grabbed a metal handled pan that was on an electric stove, and reached over to turn on the water. There was a problem with the stove, and she took the current right across her body. Her muscle spasms caused her hand to come off the faucet if it hadn’t it would have been fatal.
Circuit breakers protect wiring. A human could hold a hot wire indefinitely, and a breaker will not trip, unless more than 15 or 20 amps is passing through the human to either neutral or ground - far more than the ~30 miliamp threshold of danger.
If you’re concerned about fire, there’s a new type of breaker called arc-fault that senses “unwanted” sparks and arcs down the line. They have enough intelligence to know the difference between the arc that happens when a light switch is flipped or sparking in a motor vs unwanted arcing from a bad connection or damaged wiring.
One common scenario is lamp cords run under rugs and getting stepped on. When the insulation is eventually damaged enough, arcing can happen internally in the wire. An AF breaker will sense this and cut the power before this has the opportunity to get hot enough to start a fire. Another very common arcing scenario is bad connections at a receptacle.
As of 2002, the National Electric Code requires AF breakers on bedroom receptacle circuits in new construction. Some states go even farther and require them on all receptacle circuits in residential living areas. ie: bedrooms, living / family rooms, etc. Requiring AF breakers in remodeling projects is currently at the discretion of your local codes and inspectors.
AF breakers cost around $30-45 each, as do GFI breakers. Combo GFI/AF breakers do exsit, but aren’t terribly common yet. It is OK to use a standard GFI receptacle on a circuit protected by an AF breaker.
In a nutshell:
Circuit breakers protect the wiring itself from gross overload, but do not protect agaisnt electrocution or fires caused by arcs or sparks.
GFIs protect humans from electrocution, but do not protect the wiring against overload, unless it’s a GFI breaker.
AF breakers protect against fires caused by arcs, and protect the wiring against overload, but don’t protect against electrocution, unless it’s a combo AF/GFI breaker.
When I moved here, I hired an electrician to put GFI devices on both bathrooms and the plug to the waterbed. He also added outlets to both bathrooms. He explained that I only needed one device per bathroom, and the other outlet would be wired to it. He also wired the waterbed plug to the same ground fault interrupt device.
It’s easy to check; plug a lamp into the “downstream” outlet (official name: “Load”) and press the GFCI’s TEST button. If the lamp goes out, you’re good. Push the RESET button back in and carry on.
This is true, however, circuit breakers are a lot less fun to reset when you’re standing naked in your bathroom with a blowdryer in your hand. Especially so if it’s winter and your breaker panel is outside.
Thanks!
I almost had a fire in the house over the weekend. We are remodeling after Katrina-almost done-and are using the wiring for the first time (it has been energized for months but no one is living there yet). It didn’t pass. We used the room for an afternoon-lights and tools-and by the end of the day one wirenut behind an outlet had melted and was starting to fizz. An electrician had gone over the wiring to make sure it was safe-it wasn’t. Electricians are in great demand around here and I suspect he hurried.
I am taking this opportunity to have the service panel replaced. The panel is almost 30 years old and wasn’t very good to begin with. A new panel and a transfer switch (for a generator-hope I never need it.) will make me feel better and will improve the safety of the house.
Any idea about how long these AF breakers last? A regular breaker costs $5-$10, so this will be a considerable expense for the entire house. I have about 30 circuits.
I assume I can mix regular and AF breakers in the same box? I have some rooms where I have no reason to be concerned about the wiring and could skip those rooms.
Fizzing wirenuts? :eek: That’s the sort of thing an AF breaker can protect you from.
At about a $25 premium over regular breakers, you’re looking at about $700 more to outfit the entire home with AF’s, but two considerations: it’s cheaper than cleaning up after a fire, and depending on the scale of your repairs, the local inspector might hold you to current code, rather than grandfathering in the “as-built” 30 year old code.
You can freely mix AF, GFCI and normal breakers in a panel, provided they’re all from the same manufacturer, or if it’s all the cheapie mix-or-match universal stuff. Given the opportunity, I’d step up to something like a Square-D QO panel. Yes, it costs a bit more than the generic stuff, but it’s commercial-grade gear and will probably outlive you. I’ve had plenty of issues with cheap generic breakers not fitting properly into panels, or poor connections between breaker and bus, leading to overheating, nuisance trips and ominous buzzing, but haven’t yet had a lick of trouble with Square-D’s stuff. Their “visi-trip” feature is nice too - a tripped breaker will sprout a bright orange flag in the handle, making it easy to spot.
I’m not sold on the QO’s. They are good breakers in the way of overall performance but they aren’t the easiest to install (you have to be careful when snapping them in, I’ve had them shoot out of my hand 'cause they wouldn’t seat easily) and I have seen the tabs that grab the bus be too stretched to make a good contact (that could happen with any breaker really).
Just personal experience, but for commercial apps I like to use the bolt on breakers, and for homes I like Cutler Hammer CH, (not BR) breakers and then Homeline and GE next.
passwords
Also, keep in mind that SqD doesn’t make a 60 amp 240v GFCI breaker for hot tubs (they make a 50 though).
I had to scab on a sidecar from Cutler with appropriate breaker 'cause the tub required a GFCI 60 A service.
IIRC, devices may not be returned to service once they have been immersed by flood. Devices includes: circuit breakers, switches, receptacles, and wire nuts.
The problem is that flood water includes petrochemicals, sewage, pesticides, and anything else in your garage/shed/basement and those of the umpteen thousand other folks whose houses and outbuildings have contributed to the unknown brew.
UL doesn’t issue a listing for devices based on anything other than installation consistent with manufacturer instructions.
Thanks
I am looking forward to a new service panel. I agree that it is worth the extra cost to get a high quality panel.
One thing that surprised me is how hard it is to get high-quality outlets. I have had to order them both times I needed them. By high-quality I don’t mean “hospital grade-a term I just learned” but something better that the cheap walmart specials. I had to order the Cooper backstab clamp type. Not even te electrical supply houses I visited has them in stock.
Absolutely!
Fortunately I only had 2 feet of water so the only electrical components I lost were the outlets. Along with all the furniture, walls ,appliances etc.
The insurance company was comfortable with allowing the wire itself to stay. They used to replace it, and on the really badly damaged homes they did, but on most homes we could keep the wires. As with most things that was a mixed blessing. One of my neighbors burned down just two weeks before he was to move back in to his house. The hypothosis is that a staple had nicked the insulation and over time the corrosion built up to cause a short and fire. At least that is what the fire inspector said. I know the owner, it wasn’t a case of selling out to the insurance company. He had just rebuilt.
Okay, I posted in this topic yesterday, I know I did, went and found a link and everything. But nothing here.
Guess I will try again. You might want to consider a whole house surge protector. It doesn’t completely eliminate the need for a strip for your computer or stereo, but it helps protect things like your refrigerator, washer/dryer, and other things like that. I found out about them watching This Old House and called the electrician rewiring the house I bought the next day to see about getting one added.
They range in price from less than $100, to something like I got, $400 with protection for wiring, phone, and cable lines and a $50,000 insurance policy against failure.
Here is an article about them at the This Old House website.
The term you’re looking for is ‘commercial’ grade outlets, those are the ones you want.
Sounds like you got the best ones you could (the back insert with screw clamps). I prefer those too.
You don’t want back-stab (pressure fit) or the ‘spec’ grade with just the screws and no clamps.
Make sure your grounds are all continuous and that any metal boxes are bonded.
Don’t use the outlet’s ground screw for more than one ground (make the splice in a wire nut and bring out a tail to the ground screw).
What happens with wiring (most romex and BX and other ‘rope’ type wiring) is that they have a paper lining in them that will wick up the water and retain the moisture in the cabling. That can lead to breakdown of the insulation, corrosion, shorts, etc.
When houses are wired the roof and shingles must be intact before the electrician is allowed to wire the home. This way rain and moisture is kept from reaching the open ends of the cables that are installed. A flood sort of defeats that purpose.
