About a month ago, I was at the supply house and noticed AFCI breakers, and since I thump the tub on SDMB about electrical and fire safety, I bought and installed them in my panelboard, providing bedroom circuit protection, per the 2005 NEC. Cost for two 15A units was $65. The shoemaker’s son is no longer barefoot.
These devices are available for most current panelboards (Square D, GE, Cutler-Hammer, Murray, Siemens), and can be found at big box stores, as well as electrical supply houses.
Ask whatever questions you might have. They will be answered by me or one of the other qualified electricians who hang out around here. Most importantly, put this on your urgent “to do” list, and protect your family and home from a potential electrical fire.
I have nothing of use to add, other than that I did not understand one effing thing you said in that paragraph.
You bought some circut breakers and put them in the tub and got some shoes for them what?
One of the problems that confuses folk about these devices is discrimination and diversity, could you explain these in a simple manner so that the assembled masses can finally understand that its usually better to have a split mains box with AFCI breakers for some circuits and not others.
It can be a real pain to find that you try to do a spot of welding and suddenly everything goes dark.
PS. we have a wired earth system over in the UK rather than the 2 wire one I belive you use, so I’ve always wondered where the ground current goes - ours is pretty straightforward, it goes to source and the resultant live neutral imbalance trips it out
A general question about updating an electrical system to be safer: the wife and I are house-shopping right now, and considering a house which currently has two-prong plugs throughout most of the house. What would be involved in updating the electrical to a modern system, with grounded outlets throughout and GFCI and/or AFCI where needed for maximum safety and general coolness? Is this a huge job?
I don’t propose to fully understand wiring in the UK-my comments are US based. That being said, my arc welder is connected to a 240 receptacle which isn’t AFCI protected, but even if it was, the branch circuit feeding the receptacle would, in theory, only see the primary transformer winding of the welder. I don’t know if the arc signature experienced by the secondary would transmit to the primary via EMF and trip the breaker.
The 2005 NEC requires AFCI for bedrooms of 1 and 2 family dwellings. The 2008 edition expands application to other habitable areas of 1 and 2 family dwellings, but does not include garages, carports, or outbuildings, where one would typically employ an arc welding appliance.
Please let me know if that fails to answer your question.
What you’re calling a split main was used in the US when fusing was the widespread means of overcurrent protection. One main two pole pull out disconnected the range (usually the only large draw 240 volt device), and the other pull out disconnected small 15 and 20 ampere branch circuits. This arrangement met the “not more than six actions” necessary to disconnect all power to a dwelling unit.
Impossible to say for sure without inspecting the site, but it certainly could be. GFCIs and AFCIs don’t require a ground to function properly, but obviously grounded outlets aren’t very useful without one. OTOH, you really can’t trust grounding which relies on connections between conduits and fixture boxes; you really need good ground bonding via copper. If all the wiring is two-wire with no ground, you’ll probably want to upgrade the wiring, as well, and that can be a real PITA. You’ll definitely want to get an estimate or three from qualified electricians before going ahead with the purchase. If the grounding copper is there, just upgrading the outlets and installing AFCI breakers isn’t that big a deal.
Neither GFCI or AFCI devices depend upon a ground conductor to function properly. This is a popular misconception.
Older homes were wired in a variety of methods. Some used a ground conductor separate from the 2 wire sheath, connected to every device box in a daisy chain method. This was the case in Levittown, PA, for some, if not all of the dwellings. Another method employed a true three wire branch circuit, but instead of terminating at the device, the ground was terminated at the device box cable clamp. As such, the box is effectively grounded, and the device (switch or receptacle) connected to ground via its two mounting screws and the device strap. When using a three wire appliance, that’s why you would use a 3 to 2 adaptor, but the ground would only be effective if the duplex cover plate screw was removed, and the green ground tab of the adaptor was screwed tight.
To address your query specifically, Giraffe, I’d need to visit the dwelling and determine if either of the above conditions apply. In any event, GFCI receptacles can be installed, provided they are marked “No Ground Available”, and if the dwelling is fitted with a fuse panel, a sub panel can be installed, containing GFCI and AFCI breakers to protect appropriate circuits.
For everyone out there who is confused, allow me to translate.
Most people know what a circuit breaker is. You get an electrical fault, the breaker trips, and the power goes out. You fix the fault, flip the breaker back on, and your power comes back on.
Regular breakers only detect when too much current is flowing. That’s fine if there’s a major short circuit, but there are a lot of conditions where a person can be killed or a fire can be started without causing enough of a fault to trip the breaker.
A GFCI is a “ground fault circuit interrupter”. What this does is it measures the current going through the “hot” wire and the “neutral” wire and makes sure they are equal. If they aren’t, then it knows that a “ground fault” has occurred. What this means is that the electricity has found some other path, which is typically something like through a person and into something grounded like a water pipe. GFCIs have been around for a while. They are good at detecting faults that a regular breaker won’t detect, such as the typical “oh shit I dropped my hair dryer in the bathtub” (which won’t necessarily cause the regular breaker to blow).
One of the major causes of fire though is an electrical arc from a poor electrical connection. The bad connection can be anywhere. It could be inside a switch or outlet. It could be in a wire inside the wall. It could be a frayed extension cord. As electricity arcs over a bad connection, the connection heats up and can start a fire. That is what AFCI is for. An AFCI is an “arc fault circuit interrupter”. If it detects an arc, it shuts the power off. Arc faults often won’t trip a regular breaker or a GFCI, so an AFCI is a good thing. AFCIs as part of the standard electrical code in the U.S. are fairly new. NEC = National Electric Code, by the way.
AFCIs are fairly new, and are good at preventing fires. Danceswithcats is telling all of you to get them installed so that your house will be safer. While they are fairly simple to install, I get a little nervous when your typical do-it-yourselfer starts tinkering with electrical panels.
Thanks for the answers, Q.E.D. and danceswithcats. We’ll of course get thorough inspections done on any property we end up buying, but it’s good to know that at least two-prong outlets aren’t automatically a huge rewiring job (because otherwise the house is pretty nice). And I hadn’t realized that GFCI and AFCI didn’t actually require grounding to work properly – very interesting.
No, those are GFCI outlets. The OP is talking about AFCI breakers–these replace a standard circuit breaker in your load center (what you’d likely call the fusebox or breaker box).
But, what do you mean “turn on the outlet first?” The only time those are meant to be off is after tripping due to a fault or after testing. They can be reset immediately (although if it keeps tripping, you’ll want to investigate why.)
Just got done rewiring a 1917 house (my own - allowed in my city as long as it gets inspected), replacing knob and tube circuits, and added AFCIs to the new bedroom circuits per code. This is a second-house, so it sat vacant for a week. Once when I returned, one of the AFCIs had tripped.
The question is - are AFCIs prone to tripping due to other conditions besides arcs? For example, would a lightning storm potentially cause problems? Or do I have a probable bad connection somewhere (I know where I’d start to look).
Really? I’ve been replacing two-prong outlets in my house as needed with grounded outlets, taking advantage of the return path offered by the aluminum conduit from the outlet to the breaker box, and testing each installation with a circuit tester like this one. Should I not be doing this?
The problem is that those testers indicate a ground path is present, but don’t indicate the quality of it. The principle behind grounding and bonding is to create a high quality, low impedence, path (read: better than you) for fault current to follow such that the overcurrent protective device (fuse or breaker) opens quickly, reducing danger to persons and property.
Aluminum readily forms a layer of oxidation on its surface, which is why conductor terminations are treated with an anti-oxidant when they are being made up. Aluminum connections need to be properly tightened to a specified torque value for long term reliability and safe performance.
Years ago, UL subjected a number of device box and conduit assemblies to tests designed to indicate their ability to clear fault current. Although the faults were cleared, those wrench tight connections still produced significant amounts of arcing. As such, it’s preferable to have a separate grounding conductor which is properly terminated to clear any faults encountered.
Rather than edit, let me add this: when you say ‘aluminum conduit’, are you speaking of a smooth-walled piece of pipe through which the hot and neutral conductors were pulled, or are you speaking of a flexible, corrugated metallic product with two paper-wrapped, insulated copper conductors and a bare aluminum conductor within?
The stuff I’m calling conduit is very similar in appearance to this. It’s a 1937 U.S. home, and this stuff seems to run from the breaker box to the outlets with two copper wires within. I was under the impression that I could safely ground each outlet to its box, and rely on the conduit to provide a path to the grounded circuit-breaker panel.
That product is known as Flexible Metal Conduit: Type FMC, and is covered under NEC Article 348, and has use for protecting motor leads, and as a component of lighting systems. At 348.60 Grounding and Bonding., we read, in part: FMC shall be permitted to be used as an equipment grounding conductor when installed in accordance with 250.118(5).
250.118 Types of Equipment Grounding Conductors., The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:
250.118(5) reads: Listed flexible metal conduit meeting all the following conditions:
a. The conduit is terminated in listed fittings
b. The circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.
c. The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible metal conduit in the same ground return path does not exceed 1.8 m (6 ft.)
A further check of the UL White Book, 2007 edition, under Flexible Metal Conduit, listing DXUZ, states in the third paragraph: Flexible metal conduit no longer than six feet and containing circuit conductors protected by overcurrent devices rated at 20 A or less is suitable as a grounding means.
From the above, I conclude that a receptacle connected to your fuseboard or panelboard by 6’ or less of FMC is effectively grounded, but any devices employing a greater length, or daisy chained from that first device box are not effectively grounded.
Because they are visually quite similar, don’t confuse FMC with type AC, or armored cable, aka BX, or type MC. Type AC has a bare grounding conductor which is in contact with the corrugated sheath along the length of a cable run, and when proerly terminated, may serve as an equipment grounding conductor without length restrictions. Type MC has an insulated grounding conductor along with the current carrying conductors.
