Knob and tube fixture replacement.

[ritelec]

Box............. what are the old boxes that knob and tube wiring enter for lighting fixtures called ?

They ones that just have a thread for the threaded hickie to screw on to go to fixtures after gas lighting era.

They're not really boxes.. but are they still called boxes??

As an electrician, legally that it doesn't have a "box" and there is no ground, am I still able to install a metal fixture which needs ground?

I have a couple to install and has me thinking... the owner also wanted a fan/light installed but after I started mentioning I would have to install a fan rated box... and new rx wiring...... well she said she would return the fan and just have me install a light.

Can I "Just" install a light?

Thank you

 

[ptonsparky]

Can you find a fixture that does not require an EG?

Probably no way to connect a new fixture to old wires. I see new NM, and an AFCI.

 

[ritelec]

Probably no way to connect a new fixture to old wires. I see new NM, and an AFCI.

ouch

 

[user 100]

Box............. what are the old boxes that knob and tube wiring enter for lighting fixtures called ?

They ones that just have a thread for the threaded hickie to screw on to go to fixtures after gas lighting era.

They're not really boxes.. but are they still called boxes??

As an electrician, legally that it doesn't have a "box" and there is no ground, am I still able to install a metal fixture which needs ground?

I have a couple to install and has me thinking... the owner also wanted a fan/light installed but after I started mentioning I would have to install a fan rated box... and new rx wiring...... well she said she would return the fan and just have me install a light.

Can I "Just" install a light?

Thank you

The technically correct name for those "boxes" escapes me at the moment- Al Hildenbrand has mentioned them here before- maybe he'll see this and share his wisdom.

To be compliant, consider these options:

1) a short stretch of 90c conductors (new nm) from jbox to new box if the new fixture requires such conductors.

2) Heat shrink the old conductors, put old conductors in new plastic box- arlington makes a few smaller sconce boxes that are good for this.

And you do have the option of hooking up a new fixture sans an egc provided there is gfci protection ( you would need afci too-think obc dfci) ahead of the fixture- see 410.44 exception 3....

However, strictly from a code standpoint, if choose option #1 with the new NM, you have *technically* extended an old ungrounded ckt, which isn't legal- you would have to connect the egc in the new nm to any of the areas listed in 250.130(C)(1 thru 5) for that to be totally kosher- the gfci doesn't get you out of that. But ITRW, in this type of situation, the egc in the NM almost never gets connected to a true egc or the short section of bare egc in the new nm gets removed entirely......

 

[jmellc]

Last I recall, you could install a keyless socket or other type of light with no exposed metal parts.

 

[al hildenbrand]

Box............. what are the old boxes that knob and tube wiring enter for lighting fixtures called ?

They ones that just have a thread for the threaded hickie to screw on to go to fixtures after gas lighting era.

They're not really boxes.. but are they still called boxes??

I'm curious what it is that you have seen at this customer's building, as I can't quite figure out what you mean. I can understand, from what you write, that there isn't existing gas piping present at the Lighting Outlet.

In my work area, the buildings wired early in the K&T era had a simple "tripod" wood screwed through the plaster to the lathe or anything else that might be a backer or framing. The individual conductors, in loom, were simply mudded in place (although there were lots of ways the loom & conductor were fixed in place during roughin, prior to lathe and mud).

The loom-in-plaster is "boxless". To hang a new fixture today requires cutting in a box.

The flat pan was popular in the first half of the 1900s, but relied upon the volume inside fixture canopies. Flat pans are almost impossible to use today to meet modern cubic inch requirements, so, again, a new box is required to be cut in.

 

[ceknight]

Box............. what are the old boxes that knob and tube wiring enter for lighting fixtures called ?

"pancakes"

 

[ceknight]

In my work area, the buildings wired early in the K&T era had a simple "tripod" wood screwed through the plaster to the lathe or anything else that might be a backer or framing.

That's neato. In 30 years of working on old houses in the Syracuse area I've never run across one of those. It's always the old pancakes here.

The flat pan was popular in the first half of the 1900s, but relied upon the volume inside fixture canopies. Flat pans are almost impossible to use today to meet modern cubic inch requirements, so, again, a new box is required to be cut in.

I think you can still use the canopy for box fill if it's marked for such. Always make sure you're carrying a Sharpie so you can mark it yourself just in case it isn't.

When I run into pancakes for wall sconces that are right on a stud, I replace the old pancake with a new 4" pancake and sneak one 14-2 into it. It's the most you can get away with but it'll get you out of a tight spot.

 

[al hildenbrand]

I think you can still use the canopy for box fill if it's marked for such.

I think revision to 314.16(B)(1) Exception changed that a couple Code cycles ago. Now there is an allowance for a light fixture's leads (up to four smaller than #14) to be omitted from the Box Fill Calculation if the fixture is domed or has a canopy.

There is nothing, now, in the language that allows branch circuit conductors (#14 and larger) in the ceiling box to spill into the canopy . . . by calculation.

Right now I'm referencing the 2014 NEC.

 

[kwired]

If still in original condition I don't think I have ever seen a "box". Maybe some sort of adapter to thread a stem into but conductors still emerge directly from plaster usually encased in "loom", maybe occasionally have porcelain tubes instead of loom.

 

[ritelec]

thank you........ I'll take a pic when I get back there.
It's similar to the pic al hildenbrand posted but not the same.

similar metal. size of a 3 " pancake box. no clamps, but the openings like on new boxes is where each separate wire would enter, one in each opening.That threaded part as pictured is flatter down to the depth of the box.

four little (regular sized or smaller box holes) around center for mounting.

Yeah, don't know what to do. Lady doesn't want to spend "any" money.
two family house with a old single family service on it (federal pacific and fuse box)..

I removed 3 fixtures to see what was up..

I put 3 pigtails on the knob and tube wires...

Should I put the fixtures back the way I found them??

:- ) ..........................always something. smh

Thanks gents

 

[al hildenbrand]

size of a 3 " pancake box. no clamps, but the openings like on new boxes is where each separate wire would enter, one in each opening.That threaded part as pictured is flatter down to the depth of the box.

four little (regular sized or smaller box holes) around center for mounting.

Sounds like a standard "fixture stud". Also known as a hickey. The one shown below will stand proud of a 1/2" flat pan. A common variation was to have the four feet on the outside top of the box with the threaded stud down through the center K.O.

I suspect the one you are seeing is a squat version made for the inside of the flat pan.

Sight unseen, I think you have an actual "box" present. There are probably no threaded 8/32, or even 10/24, screw locations in the box . . . so the way to hang the luminaire is to get a "gofrom" fixture bar that can be mated to the 1/8" iron pipe, 1/4" iron pipe or 3/8" iron pipe threads that are present. There may be the need for a short extension of the hickey. That is, if the other bits of the Code were ignored.

 

[ceknight]

I think revision to 314.16(B)(1) Exception changed that a couple Code cycles ago. ......There is nothing, now, in the language that allows branch circuit conductors (#14 and larger) in the ceiling box to spill into the canopy . . . by calculation.....Right now I'm referencing the 2014 NEC.

We're using the 2015 IRC, which still has it:

E3905.12.1 Box volume calculations. The volume of a wiring enclosure (box) shall be the total volume of the assembled sections, and, where used, the space provided by plaster rings, domed covers, extension rings, etc., that are marked with their volume in cubic inches or are made from boxes the dimensions of which are listed in Table E3905.12.1. [314.16(A)]


So I can still use my lame sharpie joke with inspectors.