kwired
Electron manager
- Location
- NE Nebraska
And when incandescent lamps were still prevalent, things were often compromised by over size lamping anyhow.
Yeah but how many places that old still have the original lighting and switches?
Through the knobs?The easiest way is to disconnect the knob and tube and use it as a pull string for a new whip.
Why not AC or MC, no length limitation.There's also limitations to lengths of FMC, which can make things tricky.
I've worked on many K&T houses that still had the original lights, switches and receptacles. Love those original push button switches. Also the surface mounted rotary switch.Just add new grounded receptacle runs, leave old ones in place.
Through the knobs?.....
What do you mean "through the knobs?" I think you mean "through the tubes?" And if so, obviously not. You'd have to knock out the tube.Through the knobs?![]()
I mean, technically speaking those aren't FMC. FMC is a specific raceway type with it's own NEC article, but I think you're playing with fire there.Why not AC or MC, no length limitation.
We love K+T replacement type jobs around here. Chicago and the surrounding areas have a ton of K+T wiring.I've been told in the past by my elec instructor that when a home inspector flags K and T wiring, you don't need to do anything with it as long as it hasn't been insulated around. Whether in the attic or in walls, it is fine to leave it active as long as no insulation is touching it as it could overheat. Is this your experience ? The home inspector can recommend replacement but that is not required.
Thanks.
3/8 FMC is what has limitations on what it can be used for and it is more than just length restrictions, See 348.20, You are not using it for general purpose branch circuit usage though. Larger sizes have no length restrictions other than 6 foot restriction on using as an EGC, pull a green inside and there is no length restriction.Here in Chicago we have grandfather status, so unless you're remodeling what I think is 60% of the home, and are then required to bring everything up to code, it's not legally required. I still recommend it being replaced every time I encounter it.
The easiest way is to disconnect the knob and tube and use it as a pull string for a new whip.
The standard existing knob and tube hole should be just barely big enough for a 3/8" FMC, but sometimes it isn't.
There's also limitations to lengths of FMC, which can make things tricky. First floor is easy if you can get a whip pulled down to an unfinished basement and hit a box, which I typically plan to be a light of sorts in the basement to avoid randomly spotted boxes all over. If not, transition the FMC to EMT and then hit said box.
Second floor or above takes a little more thought.
I'm aware. I yell at the guys that slop it in the ceiling without strapping it, etc. I know it goes beyond just length.3/8 FMC is what has limitations on what it can be used for and it is more than just length restrictions, See 348.20, You are not using it for general purpose branch circuit usage though. Larger sizes have no length restrictions other than 6 foot restriction on using as an EGC, pull a green inside and there is no length restriction.
FMC is not limited to 6 feet.I'm aware. I yell at the guys that slop it in the ceiling without strapping it, etc. I know it goes beyond just length.
I should be clear I'm talking more about my local municipality than I am the NEC, which limits ALL FMC to no more than 6 ft. Size is irrelevant. I've worked in villages around here that amend the NEC to say 3 ft. Around here it's probably going to go away entirely eventually, besides serving an appliance disconnect whip. We're already almost at that point.
My comment, which you originally responded to, NEVER explicitly claimed to apply to ALL instances of FMC. Nor did it ever claim to be representative of the full scope of FMC requirements.FMC is not limited to 6 feet.
It is limited to 6 feet when allowed and used as the EGC, but if you pull a green there is no length limitation.
There is no unsupported whip rules that can apply either when over six feet, so if your whip is more than six feet you need to follow the general support rules.
I then responded by agreeing with you that I'm aware there are additional requirements and that I often yell at guys who try to avoid meeting these additional requirements when they slack a long run of FMC through the ceiling without strapping it (as one example).FMC is not limited to 6 feet.
It is limited to 6 feet when allowed and used as the EGC, but if you pull a green there is no length limitation.
There is no unsupported whip rules that can apply either when over six feet, so if your whip is more than six feet you need to follow the general support rules.
since AC and MC are cables, it is hard to consider them as flexible metal conduit types.
I mean, technically speaking those aren't FMC. FMC is a specific raceway type with it's own NEC article, but I think you're playing with fire there.
I take limitations on FMC to generally apply to all flexible metal conduit types, including AC and MC, just to avoid problems.
Technically speaking you would be correct if the limitations are explicitly applied to FMC.
Yes and no. Not a debate I really feel like having. Are they technically different? Yes. Do I consider them different? No, not really. Again, not a debate I really feel like having because I can already see where this is going, lol.since AC and MC are cables, it is hard to consider them as flexible metal conduit types
Once again you're putting words in my mouth. I never said there is a "general length restriction on FMC" according to the NEC.Sorry I ruffled your feathers, but as I see it there is no general length restriction on FMC.
There is restrictions on use of 3/8 and you won't be using it for general use purposes like you can for other sizes.
For the other sizes only length limitation is how long it can be if used as the EGC, and in some cases it can't be used as the EGC anyway.
You can wire an entire building with FMC if you wanted. You will be pulling an EGC in nearly all of it if you do so.
AC and MC cables, even though they may look similar - fall under different section in the code. AC and the newer MC-AP or similar, are designed so that the sheath is part of the EGC and has no length limitation relating to this aspect. Regular MC the sheath is not part of the EGC, no length limitations there either.
What do you mean "through the knobs?" I think you mean "through the tubes?" And if so, obviously not. You'd have to knock out the tube.
I'm not talking an end-to-end pull, like from fixture all the way to panel. I'm talking an opening to opening pull, like switch to light and obviously making a few cuts as needed... like removing an existing outlet, cutting the dead cable, stripping it, and pulling a whip down to an unfinished basement (6 ft).
A full run pull would be impossible, yes.
I mean, technically speaking those aren't FMC. FMC is a specific raceway type with it's own NEC article, but I think you're playing with fire there.
I take limitations on FMC to generally apply to all flexible metal conduit types, including AC and MC, just to avoid problems.
Technically speaking you would be correct if the limitations are explicitly applied to FMC.
I thought you meant tubes because pulling something "through" them being difficult makes more sense as the tubes already pass "through" something. Ultimately knobs or tubes makes no difference. It's common sense that you can't pull anything "through" either of them.I meant the KNOBS! Those things holding the wire off the wood on runs parallel to the wood (joist or stud). No way can you pull anything through a knob correctly installed, the wire is just not going to move. Of course the new cable can just be fished through the stud /joist space without support for re-work, skipping the knobs. But then the existing wire cannot be used as a pull rope. That was my point.
And yes, the NEC limitations ARE explicitly applied to FMC, not AC or MC cable. Around here we wire entire commercial buildings with it. And no, I do not play with fire. Learned from Mrs. O'Leary.....![]()