Will AFCI’s help protect my old house?
I live in a 80+ year old house, with all the attendant old house problems. Of course the electrical wiring needs a lot of help. I plan to rewire the house, but it will have to be done a bit at a time. I was thinking of replacing the circuit breakers with AFCI’s first, hoping to reduce the chance of a problem until I can start pulling wire. Is this a good idea, or a waste of money?
Assuming I do this, are there any circuits/situations where an AFCI shouldn’t be used?
“You couldn’t pay me to run into a burning house. I’m a VOLUNTEER!
Replies
Anybody? Anybody?
"You couldn't pay me to run into a burning house. I'm a VOLUNTEER!
Give it time. Some of the guys who can answer your question haven't even gotten home from work yet.
Hey, simmer down there, pilgrim! A few hours w/o a response and and you're frantic, already?
AFCIs are designed to cut power under certain circumstances, namely, arcing parallel faults above a certain magnitude (75 amps, if I recall right). A parallel fault is one where there's a short circuit between hot and neutral; picture the two wires of a circuit touching and arcing (or almost touching and arcing). An AFCI isn't designed to address arcing series faults, where the hot conductor has a break in it that's shooting sparks (arcing).
AFCI breakers also function as regular overload breakers, cutting off power if there's an overload or a short circuit. AFCI breakers also, depending on the type, have a "GFPE" feature, which stands for "ground fault for protection of equipment". This is similar to a GFCI, except that a GFCI trips at 5mA (+/- 1mA) and a GFPE trips at 30mA of ground fault current.
The point is, AFCIs will enhance safety but are not a panacea. If you have a breaker panel for which AFCI breakers are available, go ahead and put 'em in. If one or more trip, it might be nothing, or it might be a real problem. Then you'd better call in a very good troubleshooter or re-wire that circuit forst.
Keep in mind that the AFCI is a pretty complex device (the price alone ought to suggest that). They can be tempermental. And they can be bad out of the box; Square-D, one of the best-respected manufacturers of electrical equipment, recently announced a recall of a lot of their AFCI breakers.
Good luck,
Cliff
Sorry guys. Didn't mean to seem impatient. I was trying to make a "Ferris Bueller's Day Off" joke. I guess it was a bit weak.
Thanks for all the advice. Maybe I'll go with the GFCI's to start with."You couldn't pay me to run into a burning house. I'm a VOLUNTEER!
It seems as if you would be better off with installing GFCIs. This will give you better protection against line to ground faults than an AFCI. I don't understand why an AFCI would tolerate a 74 amp line to neutral fault without tripping.
The NEC Code panel was really bamboozled on this one. Some states have wisely deleted this stupid requirement.
~Peter
I am sure at least one lurking viewer of this forum looks exactly like Martha Stewart. You know who you are: blonde, double EE, shapely legs, petite feet. Report to the visitors center at Altendorf and sign in as a visitor. We will furnish you with an ultraviolet stamp.
Notice that it's a 75 amp arcing fault. That's very different than a bolted fault. The 75 amps flow for a few cycles, off and on, and that's not enough to trip either the thermal or electromagnetic mechanism of a regular breaker. I don't know why the trip point for an AFCI for an arcing parallel fault was set at 75 amps--I believe it's because anything less would nuisance trip (an incandescent light draws a very high inrush current, for instance, and of course, motors do too).
(Edit) Note that a GFI doesn't offer any protection for a hot to neutral fault. A conventional breaker will protect against an overload or bolted fault; the AFCI is intended to deal with certain kind and magnitude of arcing fault. The GFI and AFCI do different things.
Cliff
Edited 1/15/2005 2:06 am ET by CAP
Also, if I understand it correctly the purpose of the 60ma ground leakage current was to detect cables where the insulation had been overheated and starting to break down.Thus you could get leakage between the hot and ground in the cable.But most old wiring does not have a ground so that feature is does not add anything in that case.And while GFCI's do provide personal protection. IE you getting between the hot and a ground (water for example) that provide absolutley no protection against "bad wiring". So the AFCI will add some improved protection, because of the parallel arc detection.But I really wonder how effective those are without series arc detection.
Do you have knob and tube wiring?
No k&t. I believe the house originally had it, but it has been re-wired at least twice, maybe 3 times. None of them were done very well, in my humble not-an-electricians opinion. I do have quite a bit of the old cloth wrapped cable, some of my outlets are two-prong, some three-prong but no ground, and a few three-prongs that actually are grounded. It's a mess. I sometimes think this placed should qualify as a monument to divine intervention!"You couldn't pay me to run into a burning house. I'm a VOLUNTEER!
By no means a pro electrician, here, but I have sympathy for your situation having just finished the rewiring of a K&T-mix house. others would have focused only on replacing what was known to be K&T (or worse only hiding that K&T existed) but we actually also made sure we knew how every circuit was run, because it was the non-original stuff that was most alarmingly stupid.
From what we know about the ACFIs, they are required to protect bedroom plugs but you should not put lights on the same circuits as that can cause tripping problems. Or so we were told.
Our new ACFI circuits serve plugs, but not lights, and no plugs outside of bedrooms. So our whole new panel has only 4 of the expensive ACFI breakers [Siemens]. If you can find the 'first' outlet on a linear circuit of your old wiring, you could replace that outlet with a CGFI outlet and offer some protection over what you have now. That's better than just non-grounded current outlets - and make sure your CGFIs are working properly.
Note: about living through a gradual re-wire. Your old wiring could be really weird with all kinds of sins committed by previous owners. This will almost certainly include weird branching and lashing-in, buried boxes and connections buried and not even in boxes, which you will want all gone. It could be very risky working around this stuff gradually. The neutrals are often wired in loops or serving more than one breakered circuit of hot wires. You can even have loops and inconceivable branching in the hots. Be very very very careful to make sure everything you are working on is really really really dead.
We opted to be conservative on the side of doing without electricity in segments of the house for extended periods of time, as opposed to trying to use old circuits while altering them in stages, or risking having anything live in a wall that was being drilled into or fished along. Nothing was hooked up unless we knew how it traveled all the way from the panel to where we needed it without having to trust any ghost about what 'must/should/might' happen in between.
"From what we know about the ACFIs, they are required to protect bedroom plugs but you should not put lights on the same circuits as that can cause tripping problems. Or so we were told. "Actually the starting with the 2002 code ALL OUTLETS in a bedroom are required to be AFCI protected. That include lights and smoke detectors.Frankly I don't see it. And am afraid that it can cause more dangerous problems with the smokes being on an AFCI then it will prevent. A smoke circuit should be very, very, very, very low on the probablity ever having an problems. You can't overload it.But it depends on which version of the code that your community has adopted and whether they have modified it or not.