In a small job I am replacing all outlets in a house. They have metal box with BX cable and the outlets do not have grounding wire to the box. I think the screws were the grounding connection.
The new outlets are “preferred” level outlets from Homedepot. They have brass strip on one end. Can I use these self grounding outlets and consider the job done? Researching on this, I read that brass strip must contact the metal box and screw alone is not acceptable connection. Is this because screw might loose connection somehow, such as rust?
Thank you in advance.
Replies
I don't understand. Are you proposing to use the box, connector, and BX armor as a bonding conductor? If so, I don't think this is allowed.
Ground 'em.
Return those receptacles to HD and get the ones that have a grounding screw. Also buy a bunch of precut, prestripped green leads with one end wrapped around a green screw. Why not do it right and also gain some peace of mind for about $1 a receptacle.
It sounds like you have an older wiring method known as 'armored cable.' With that method, the cable jacket, box, and the connection between the device strap and the box was the ground path. Existing installations are fine, and you are allowed to continue using this method with repairs.
All UL-listed receptacles that have three openings have a ground screw. The strap of the device is also connected to the ground prong opening.
In the past decade or so, rules regarding grounding have tightened up, and this method is not allowed for new construction. Yet, it is unlikely that the box has the room or an anchor point for a grounding pigtail - nor would a pigtail address any concerns about using the cable jacket as your ground path. That is why I advise you to also protect your circuit with a GFCI breaker. Again, your boxes probably don't have room for a GFCI receptacle; older device boxes are much smaller.
First thank you all for the replies.
The system is armored cable. Thank you Amish Electrician for the clarification.
GFCI breaker is not in the budget for the HO. The outlets will be replaced the same as the original.
Again, thank you.
I have still not heard why a self grounding receptaclle will not work.
406.3(D)(1) says you can use a grounding receptacle "Where a grounding means exists" (your AC cable 250.118(8)) and 250.146(B) recognizes the self grounding receptacle as providing a path from the box to the yoke. The only thing I would do is test the ground integrity with an outlet tester.
These are all 2008 NEC references
Do you guys have to use what we call "anti-short bushings" with flex (BX or AC) connectors? They are little red plastic sleeves that you stuff into a box connector and are intended to stop a sharp burr on snipped armor from penetrating the NM coating on NMD wire.
Seems to me that these bushings could also interrupt a bonding path. Perhaps this is one reason these "self grounding" devices aren't allowed any more?
The bushings go into the cut end of the cable, not the connector. They don't interfere with the connector in any way. A listed connector bonds the AC cable sheath to the box and the sheath is the grounding conductor. AC cable is still made and sold, and it's still code for many applications, even for new work.
Self-grounding receptacles have a little wire near the screws that makes positive contact with the edge of the box when you screw the device in -- if you do it right. If you had to do 100 receptacles this would save you lots of time not screwing a ground wire to the back of each box. It's a convenience, like the much maligned backstab receptacles where you don't even need to tighten a screw. If the OP is careful installing them he's not going to have problems.
Personally I prefer to add a ground wire. I've never seen a metal box that didn't have a hole in the back that would take a #10 screw but you can always drill a hole. The green screws are usually self-tapping.
Self-grounding recpetacles O.K.
To the OP, what you're proposing, using seld-grounding receptacles with metal boxes, is perfectly adeuate and Code-compliant. The strap of the receptacle has to be in direct contact with the metal box (meaning that the box has to be dead flush with the wall surface), for a self-grounding device to be properly grounded.
As to some of the other comments, especially "do it the right way and use a grounding pigtail", three things:
1. why do you think a pigtail is better?
2. show me the Code section that suggests that a self-grounding device, properly used, isn't acceptable, and
3.almost universally in commercial work, where there's a metallic raceway system and metal boxes, self-grounding receptacles and switches are used. The number of people using the devices in a commercail occupancy is much greater and the devices are typically subject to harder usage in commercial occupancies than in a residential occupancy.
The device grounding achieved with self-grounding devices is just as good as with a pigtail to the box. I know, because I've tested quite a number of both for grounding impedance.
Cheers,
Cliff
I think the pigtail is better because the grounding isn't then compromised if the box is recessed or the strap otherwise doesn't make good contact with the box. But I agree with you that self grounding receptacles done right are "acceptable." However, since we're talking about an older residence, would you expect to find no problems with recessed boxes?
Good point...
about the recessed boxes. That''ll vary with each box. What I've seen in older houses (like those with BX and metal boxes), is that the craftmanship is pretty good. If the house is plaster over rock lath, it may well be that the box face is flush with the wall. That's the real issue, not that self-grounding devices provide a less-effective ground than a pigtail.
IF the box face is recessed, it's pigtail time.
The boxes the OP is dealing with probably don't have a tapped hole for a 10-32 screw. If that case, here's a hot trick:
http://www.amazon.com/Greenlee-DTAP10-32-Combination-Drill-10-32NF/dp/B000FCGRXM
One of these drill and tap bits and a short 1/4" hex extension make very quick work of grounding an old box. A drop of cutting oil or even WD 40 on the bit prolongs the life of the bit. Another tip: run the drill at a very low RPM once the hole is drilled, and stop and reverse to back out as soon as the bit gets fullly into the tap part. IF you run the bit all the way past the tapping part, and then reverse and back it out, the threads are usually cut twice, and so are oversize.
Last tip: if you're doing a lot of boxes, get a 5/16" nutdriver and use it to drive the grounding screw. Much easier than using a screwdriver.
Cheers,
Cliff