| Author | Message | ||
| ChuckMC9 (Chucks)
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I'm about 2/3rds through installing my receptacles and as it stands all except one are now GFCI protected, including all galley & all bays. (Bath not done yet) Something's nagging me about this, and thought while some of us are thinking of things electrical I'd ask this. Can you have too many? Is/are there reasons you would not want a GFCI outlet? | ||
| Brian Brown (Fishbowlbrian)
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I hate to say this now, but (unless I'm wrong) you could have used a whole-house GFCI on your main breaker. One of those massive ones they sell for hot tubs for about $50 for 50A. Only one place to reset/ test. Also, the 20A branch circuit models are only $20 or so. But back to your question, though, the older ones used to nuisance-trip with motors, etc., but the newer ones are pretty darn stable. I plug big power tools into my garage one all the time and it never trips. You might consider an arc-fault interrupter for the sleeping area(s), like those required in new construction per the latest NEC. Soon, the two devices will be combined… and we’ll all be safer. BB | ||
| Sean Welsh (Sean)
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No reason, except I recommend against using a GFI on any circuit that would be a problem if it nuisance-tripped, unless code requires a GFI there. An example would be the refrigerator if you have a 120-volt model. You would not want to spoil your food due to a nuisance trip. Also, circuits dedicated to air conditioners, for example. Otherwise, go for it. It's cheap insurance. I have to add that I disagree with Brian about the whole-house suggestion, for the simple reason that GFI circuits tend to be over-protective, and can trip on circumstances that are not real faults. In which case, if you have only one unit for the whole coach, ANY nuisance trip, or even a real fault, knocks you out completely. It may cost a few bucks more for individual units, but when one trips, only that single appliance is off-line. Also, it is easier to find the source of a fault when you use individual units. For the same reasons, I advise against "ganging" several outlets onto one GFI -- it's worth a few extra bucks to put in separate units at each outlet, even if several outlets will be on the same branch circuit. Remember, the ganging capabilities and the whole-house units are really designed to save contractors money while still enabling them to meet codes. FWIW. -Sean | ||
| Lew Poppleton (Lewpopp)
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Isn't it true that you can use only one GFCI in each circuit? | ||
| John that newguy Rating: N/A |
The GFI outlets can be anyplace and a few used on any given circuit, as far as I've read on the side of the boxes.... A CBr friend of mine would trip the breakers in his house with the damned linear amp he ran in his truck... Imagine him going by where you're parked for the night.... goodbye food... I dunno.... we've lived without these NEC/industry prescriptions for so long.... You don't suppose it's all about the $$$ and not a thing about "safety", do ya'? I've had a GFI fail to trip more than once. Boy. Do I feel safe. | ||
| Chuck Newman (Chuck_newman)
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Chuck, Sean is right on point again. The troubleshooting aspect of a whole house GFI is daunting. Don't put all your eggs in one basket. If you shop around, you can get 5 to 10 GFR's for the price of one 50 amp GFCB. And you will be in the dark from time to time with it. Lew, if you have say, 6 outlets on one branch circuit, you can put a GFR on 1, or 2, or all the outlets. The NEC says where you must put them, not where you can't put them. Obviously, you cannot put a 20 amp GFR on a 30 amp dryer circuit for example. Chuck Newman Oroville, CA Sean, how's your engine overhaul going? | ||
| ChuckMC9 (Chucks)
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Thanks, guys! I'm kinda surprising myself with the quality of work I'm doing (on this portion) - no bubble gum or duct tape!  Could it be that I'm actually doing something the way it's *supposed* to be done?! Wow! I'm in debt all of you. | ||
| David Hartley (Drdave)
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Has anyone actually tested a GFCI outlet when used with a non-sine wave inverter under load? I haven't yet but most outlet GFCI's are so finicky that now I am starting to wonder about that.... Spikey waveforms can do some strange stuff... | ||
| Brian Brown (Fishbowlbrian)
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All right, I'll concede the main breaker GFCI. But I still would use a 20A GFCI breaker for a dedicated branch circuit to a bathroom or kitchen. I did just that in my house when I wired up my kitchen addition and love not having to look at the ugly GFCI receptacles. Plus, my kids tend to play with the test buttons on the receptacles. The new kitchen breakers haven't tripped yet in a year, but maybe rolling houses are subject to more ground faults or nuisance trips, dunno. BB | ||
| John Jewett (Jayjay)
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Lew, once you install a GFCI, you can put 5 more downstream from it. i.e. the load terminal on the GFCI becomes the feeder for the other 5. Virtually every provision of the NEC is the result of multiple cases of serious injury or death, or life threatening fires. Likewise nearly every provision has also been run through the courts via litigation. Sadly, most frequently wrongful death suits. Yes, Jtng, unfortunately you're correct about certain parts being about money, although I feel this is not as prevalent as most people like to think. I know that the more I have learned about the Code and it's real world implementaion, the more I appreciate it for it's practical worth. The biggest hazard to the Code are the well meaning, but grossly uninformed individuals that want to use it to grind their own axe. The above notwithstanding, it's still the best thing (with the exception of OSHA) that ever happened for the American public. IMBO. ...JJ | ||
| ChuckMC9 (Chucks)
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David, for the time being I've been using a cheapo Vector 750w inverter, and it has performed just fine with the outlets I've installed so far. No huge loads, but up to about, say, five amps. | ||
| John that newguy Rating: N/A |
JJ- I'd use the GFI at the external outlets exclusively and forget the interior, with exception to the bathroom. No-one likes to get zapped, but there is such a thing as "overkill". The absolute best protection is the simple test of the power source when at the source. The reversal or polarity; the reversal of ground and power, is the most common of problems. If the testing of this is stressed, then no GFI would be necessary. Cheers. Better days are coming! | ||
| Pat Bartlett (Muddog16)
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Most nuisance tripping of GFI's are caused by numerous grounds coming from mutiple systems in buses! Vanner recommends one main ground through the Inverter ground,(carring all of your grounds back to one location) this should stop nuisance tripping! Vanner even suggests isolating your generator chassis ground and returning it through the Inverter! Mutiple ground wires will increase the possiblity of stray voltage(difference in potential) between grounds, and causing those pesky nuisance grounds, but you have to remember the GFI is just trying to do the job it was designed to perform! | ||
| Chuck Newman (Chuck_newman)
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A ground fault interrupter (GFI) whether being used as an outlet or as a circuit breaker makes no use of or reference to ground (as opposed to hot and neutral). The GFI works by measuring the transverse current in the hot and neutral wires only. If you have wired a ground fault circuit breaker, BOTH the hot and neutral wire feeding the branch circuit are connected to the GFCB. The extra white reference wire on the GFCB is connected to the neutral bus bar, not the ground bus bar. Likewise, a ground fault receptacle (GFR) does have a ground screw lug on it, but that is not used to make the ground fault "portion" of the receptacle work. The green ground lug on the GFR is merely to ground the grounded socket on the receptacle to meet the code requirements for a grounded circuit. For example, the NEC allows you to use a GFR or a GFCB on a 2 wire ungrounded circuit. Again, this is because the electronics in the interrupter does not use the ground wire to operate properly (unless you're using it as an outlet.) I'm not saying you don't need a grounded AC system. You do need it for protection, but the circuit interrupter DOES NOT use the ground for a reference. Current should only be on the hot and neutral wire. Any current on the ground wire is leakage to ground from a defective appliance or fixture. If you become the conductive path between a leaking current device and ground, that current through you now reduces the balanced current between the hot and neutral wires feeding the device. This current imbalance is what trips the interrupting device (GFR). Nuisance tripping is caused by defective appliances or fixtures, defective wiring, and radio frequency noise. Quality ground fault devices are not affected by arching unless the arching conducts current to ground. In the '70's some of the first GFR's tirpped at 3 milliamps (MA) of curent. Most now trip around 7 MA to 10 MA. This was based in research that showed the human heart would go into defibulation at 100 MA (considerably lower for animals). I had may falses with the Bryant brand of GFR at the time due to excessiverly low trip point. At times I have had very cheap units intermittently trip due to "surge current" from a starting device due to inadequate design of the GFR electronics, not due to leakage current to ground. As with many of you folks, I have had ground fault interrupters and arc fault interrupters work fine then one day you find they don't function. This is the reason manufacturers state these devices should be tested every month. It is due to the integration of electronics and mechanics -- for numerous reasons something in the package breaks down and the device stops working. It's a lot easier to understand this with graphics. Check out: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/gfi.html#c1 http://homerepair.about.com/cs/electrical/a/gfci_when_where.htm Chuck Newman Oroville, CA | ||
| niles steckbauer (Niles500)
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Thanks Chuck - I could even follow your explanation of its function - Since your quite knowledgable - How do you feel about the practical/functional use of both GFCI and AFCI protectors? Do they in fact provide the valuable protection their designed for? Thanks - Niles | ||
| Chuck Newman (Chuck_newman)
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Hi Niles, I have absolutely no doubt they provide the protection they were designed to offer. Let's look at each separately as they provide different functions. The ground fault interrupter (GFI) whether in circuit breaker or outlet form, protect people from low current ground faults through humans. They were not designed to protect circuits -- circuit breakers do that. The classic examples are someone using a hair dryer next to water in the sink, or using a drill or drop light while standing in a puddle or laying on the ground. In each case a defect in the insulation, a defect in the cord, or just getting moisture into the motor or onto heating elements can easily cause a small current to flow through you on it's way to ground -- water in sink, water on ground, on cement, or just touching another appliance with a grounded frame. An important point is "small current" here means anything less than the circuit breaker is rated for -- generally 15 or 20 amps. In the real world many people have been shocked or killed in the described environments and that prompted the design of GFI's. Circuit breakers alone were not enough. In my own experience I was using a can opener we had used for years without problem. My elbow touched our range with grounded frame and was shocked. Investigation revealed just two strands of the hot wire at the motor finally dropped down and barely touched the can opener frame. I jerked and broke contact with the range. But if you're holding something such as a hair dryer or drill, current through the body causes the muscles in the body to contract. The reason most shock victims say they tried to let go but could not. The can opener was not connected to a GFI at the time because it was before they were required on kitchen circuits. I had rented an electric motor cement mixer that tripped my outdoor ground fault receptacle (GFR) continuously. The contractor got around the problem by using a non-GFR outlet. No one was shocked because the current leakage at the motor was diverted to the green ground wire in the cord. That works until they plug the mixer into a non-grounded two wire circuit and someone touches the mixer frame while standing on wet ground. It does not get a lot of press, but many people still are killed each year by this situation. I have discovered in almost all circumstances, so called "nuisance tripping" occurs when a "current leaking" device is plugged into a GFI. Arc Fault Circuit Breakers (AFCB) have a different purpose. Today you buy a radio, a table lamp or an electric blanket or small fan, and many other consumer devices and they all have two wire plugs typically mold connected to two wires, themselves molded together. Commonly called "zip cord". These cords lay around for years and get stiff, brittle, and crack. Often this long term decay is accelerated by setting furniture on top of the cord. As of late last year, the National Fire Protection Association (NFPA) published statistics showing over 70 percent of all home fires are electrical fire starting in a bedroom. Typically the insulation on the zip cord breaks down and arcing occurs between the hot and neutral wire. The wire lays on or next to flammable material that catch fire. Simply put, the AFCB detects this arcing and opens the circuit very quickly. The GFI dosen't see anything wrong because the current in both the hot and neutral are "equal" since the arc is not going to ground. And this is the key to differences in the two devices: The GFI works by detecting more or less current in the hot wire in relation to the neutral wire. It senses an "imbalance" current condition which means "some" of the current is going to ground -- either through you or the green ground wire. Either is not acceptable. The AFCB works by detecting the voltage and current "waveform" created by various arching conditions. The AFCB is actually a smart unit that can tell the difference between the normal arcing of plugging something into an outlet under load or a motor starting, vs two wires arcing. The various types of waveforms generated by different types of arcs are in the memory of the microprocessor that control the AFCB functions. In my bus I will have GFR's in bathroom, kitchen counter, and outdoor receptacles. I have an AFCB on my house master bedroom and haven't made a decision on the bus bedroom yet. Mostly because almost all the lighting in the bus will be 12 vdc. And to my knowledge, a receptacle AFCB still is not being manufactured. And due to economics, it won't be unless required by NEC. Right now, the 2005 code says "bedroom circuit". AFCB's in the panel, and GFR's at critical outlets would give combined protection from both fault conditions. Happy bussing, Chuck Newman Oroville, CA | ||
| Mike (Busone)
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Chuck you are absolutely right about appliance cords. A while back my wife was in the bathroom using her hair dryer. I hear a loud scream and see sparks under the door. Turns out the way it was made when you wrap the cord around it the cord gets kinked really bad where it exits the unit. Over the years the insulation got really small cracks and some of the copper strands broke. She was lucky because we found some little spots of melted copper in the mirror and the toilet tank lid. Luckily the 16ga wire burned quickly and we did not have more damage. The hair dryer had a built in GFCI and the bathroom had one neither tripped. Now I replace the cord on it yearly and look it over often. | ||
| Chuck Newman (Chuck_newman)
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Mike, I'm certainly glad your wife was not injured either electrically or with molten metal. The daily twisting of the wire on hair dryers takes it's toll, and is something I didn't think of. You convinced me, as I will put an AFCB below the sink and wired ahead of the GFR. I got a small two circuit panel at Lowes or HD for about eight dollars. Dosen't take much space and is surface mounted. I'll put one in home and bus bathrooms. Life is to precious to worry about sixty bucks. Thanks, Chuck Newman Oroville, CA | ||
| FAST FRED Rating: N/A |
"Life is to precious to worry about sixty bucks." RIGHT , so the smoke detectors and carbon monoxoide detectors are already installed? FAST FRED | ||
| niles steckbauer (Niles500)
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Chuck - Thanks again for a clear explanation - You should write school books and educational manuals - its all crystal clear - Now if I only had rememory - Niles | ||
| ChuckMC9 (Chucks)
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Thanks Chuck and all - a simple little question always leads to greater understanding of more than you knew you needed to know! Much appreciated. -another Chuck |
