Hey guys. I am an electrician in NYC. The city only started allowing Romex use a few years back and I think I’ve done 1 job with it. It’s tough to teach an old dog new tricks and there is still a prejudice against Romex here among electricians and homeowners alike. People just don’t want it in their homes. I’ve been considering it’s use and figured I’d look for opinions from guys who have been using it a long time about it’s advantages and disadvantages to BX. One major hangup I have is that it seems like it would be possible to nick the hot conductor with a screw, bolt, nail, etc. and not trip a breaker if the ground wire was not also contacted. This would or could lead to energizing whatever pierced the wire as well as possibly creating a slight arcing situation in the wall building heat and leading to a fire. With Bx the armor is the ground so if its pierced and the hot conductor is compromised a short will always occur indicating a problem. Am I correct in this case and has anyone had it happen? Like I said I’m looking to educate myself on the benefits/drawbacks of Romex since I have not used much at all.
Richie
Replies
Romex is a fairly mature wiring method that is working satisfactorily all over the country but you have also done a pretty good job of defining the weakness.
We had a case in Florida where a drywall screw pierced the cable, energized the steel studs and killed a guy. Now the Florida code requires bonding steel studs.
romex pros & cons
Richie,
Out here in California, it's almost all romex (rx) in residential. Has been since the housing boom post WWII. I do resi and commercial work so I work with romex and MC, and pipe (thinwall and IMC), too.
The big plus for romex is, it's cheap in price and fast (and so cheap) to install, relative to aMC or BX. The boxes used with rx are almost always plastic (PVC) and so they're cheap, and fast to install (no KOs, no separate clamps).
Yea, nails and screws do damage to romex. I had one new house, the kitchen cabinet installer missed the stud and hit a cable, caused a bolted short. Found it by checking for continuity from the black wire in the panel to the heads of the screws holding the cabinets up...And yes, the cables were centered on the stud and met the 1.25" criteria. That's OK for drywall screws and nails, but not cab hanging screws.
I'm not sure that the armor on MC or BX would stop a screw, especially aluminum armor. I agree that a screw or nail through MC armor would be likely to trip a breaker, but then again if the point just grazed the hot conductor, you ight have a ground fault that arcs but doesn't trip a standard thermal-magnetic breaker, at least not right away.
But I do think armored cable is safer from the standpoint of rodents chewing on cables. I've seen attics with long sections of romex with the jacket and conductor insulation chewed off. The vermin seem to prefer the neutral wires. Talk about bad news for the homeowner...
Cliff
You're correct -- it happens, but not often. Probably far less often than having the conductors get nicked while cutting off the jacket of the AC.
DanH, if you're referring to rodent damage to romex, what's your basis for the statement that damage happens, "but not often"?
I've worked in buildings that are in long-developed urban areas, in older suburban areas, in ranch land, and in the urban-wildland interface. My experience is in western states and provinces, mostly in the Pacific states. I've seen hundeds of buildings with rodent damage to plastic-sheathed NM cable.
Maybe it's a regional thing.
Most professional exterminators that I've talked to say there are two kinds of buildings: those that have rats, and those that are going to have rats.
I'm not saying that every building with NM cable has serious or dangerous rodent damage to the wiring. But some do have serious damage; and in my experience, half have some "minor" damage to the cable; often, it's only the sheath that's been chewed. But then again, there could be more damage; I'm not looking at all the wiring, only the stuff that's visible or that I expose for inspection, troubleshooting, or to work on.
Cheers.
We had a bout with the roof rats here but I guess they were country rats that didn't like the taste of Romex since I inspected intensively and never found a chewed cable. They did eat some holes in the duct work to air condition their dens.
It took $100 a month off my bill when we fixed that but that was also in conjunction with installing a more efficiernt machine..
I am starting to become a fan of ENT (smurf tube) for any new wiring I do at my own house.
I was referring to his original post, about a fastener piercing the cable.
When I was doing hurricane recovery work in Puerto Rico back 10-11 years ago, they had us use UF cable in the houses, and route it high in the walls, to minimize rat damage.