K&T in light fixture

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iwire

Moderator
Staff member
Location
Massachusetts
chris kennedy said:
I see that 90C supply rating all the time. So using NM in recessed fixtures is a violation of 334.80?:confused:

No. :smile:

334.80 only effects the ampacity column we use it does not change the 90 C rating of NM for use with 90 C equipment.
 

mdshunk

Senior Member
Location
Right here.
I took out some 4" cans from the mid 1960's that were clearly stamped "Must be used with min 150*C conductors". They were wired with braided reduced ground romex of the period. I have no idea what the manufacturer had in mind when they marked those cans that way.
 

iwire

Moderator
Staff member
Location
Massachusetts
mdshunk said:
I took out some 4" cans from the mid 1960's that were clearly stamped "Must be used with min 150*C conductors".

Are you sure it was C not F?

Seems unlikely that they used the metric system in the mid 60s for fixtures.
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
iwire said:
No. :smile:

334.80 only effects the ampacity column we use it does not change the 90 C rating of NM for use with 90 C equipment.

I just went out and looked at a piece of NM. It has no temperature rating stamped on it. I see we derate MN starting with the 90C rating so the NEC recognizes it as 90C. How was this determined?
 

mdshunk

Senior Member
Location
Right here.
iwire said:
Are you sure it was C not F?

Seems unlikely that they used the metric system in the mid 60s for fixtures.
Indeed. I saved a couple purposely to take pictures. I think I'll have to cut them in half to get a good picture, because they're printed in ink on the side, inside the cans. It is definately a C.
 

480sparky

Senior Member
Location
Iowegia
mdshunk said:
I took out some 4" cans from the mid 1960's that were clearly stamped "Must be used with min 150*C conductors". They were wired with braided reduced ground romex of the period. I have no idea what the manufacturer had in mind when they marked those cans that way.

From table 310-2(a) of the 1968 Code:

Trade Name: Asbestos-Covered Heat-Resistant, Fixture Wire
Type Letter : AF
Max. Operating Temp. : 150?C 302?F
Application Provisions : Fixture wiring. Limited to 300 V. and Indoor Dry Location.
 

sfav8r

Senior Member
peter d said:
But you still can't feed a recessed light with anything less than 90C wire. So the K&T is out of the question to feed directly into the light on the j-box.

And of course I'm sure you've seen what kind of condition the old wire is in when it's been cooked by a surface mounted light. I once used up almost a complete roll of tape on one j-box that had multiple old BX cables with rubber/cloth insulation that had completely disintegrated when I took the old light down.

Apparently, the way this is done (at least according to one electrician I talked to earlier today) is to take THHN and splice a 1-2 foot piece where it enters the fixture. Loom is placed over the splice and the THHN and loom are supported on either side of the splice in accrodance with Art. 394. According to the guy I talked to, grounding has never been mentioned on any of his inspections:-? He said that he has done this fairly routinely and never been asked to ground can lights. This could be because in SF many of the installations would require running a wire down three floors to a panel , ground rod, etc to find a compliant ground.
 

e57

Senior Member
If this is in SF, some of the newer "GUNG HO" inspectors will be getting ichy over it. Especially grounding, and the total load of the circuit. (Remember initially it was rated 15A for most of the house - you could be adding 15a to each room with cans.) For a few of them, K&T re-work is a new thing. One of the newer female inspectors (Name withheld) seems to understand nothing less than removal, and gets very inquisitive everytime I see her. I have to keep my book handy when in her area.
 

e57

Senior Member
sfav8r said:
He said that he has done this fairly routinely and never been asked to ground can lights. This could be because in SF many of the installations would require running a wire down three floors to a panel , ground rod, etc to find a compliant ground.

Some will - some won't. Many of the older inspectors remember that it was only a few years ago that you could take a ground from any nearby cold water pipe. And some would even look the other way if you did...

Now heres a fun one, and i have gotten an OK to do this with some fanagling up-front during some of my multiple rough job where I have several inspectors come by the same job over time....
250.130(C) Nongrounding Receptacle Replacement or Branch Circuit Extensions. The equipment grounding conductor of a grounding-type receptacle or a branch-circuit extension shall be permitted to be connected to any of the following:
(1) Any accessible point on the grounding electrode system as described in 250.50
(2) Any accessible point on the grounding electrode conductor
(3) The equipment grounding terminal bar within the enclosure where the branch circuit for the receptacle or branch circuit originates
(4) For grounded systems, the grounded service conductor within the service equipment enclosure
(5) For ungrounded systems, the grounding terminal bar within the service equipment enclosure

Nothing says that conductor can not be spliced... Say you have a nearby outlet that originates from the same panel as the K&T circuit?

250.134(B)With Circuit Conductors.
By an equipment grounding conductor contained within the same raceway, cable, or otherwise run with the circuit conductors.
Exception No. 1: As provided in 250.130(C), the equipment grounding conductor shall be permitted to be run separately from the circuit conductors.
Means you can run it seperately, through say another newer cable that has a ground, or say some conduit that passes by with an acessible clamp. So long as it comes from the same panel.
 

mdshunk

Senior Member
Location
Right here.
iwire said:
Are you sure it was C not F?

Seems unlikely that they used the metric system in the mid 60s for fixtures.
I remembered to take a picture of these today before the scrap metal man lays claim to them.

150degreecan1.jpg


150degreecan2.jpg
 

resistance

Senior Member
Location
WA
ike5547 said:
I believe it's treated as 60 deg. in S.F.
It should be treated as 60 degrees C everywhere.
You cannot use K&T to wire recess cans, because of this temp rating. You can extend k&T to satisfy your install, but the extention of must be per code.

Also,you cannot add additional loads onto K&T circuits, because of its temp rating.
 

peter d

Senior Member
Location
New England
resistance said:
Also,you cannot add additional loads onto K&T circuits, because of its temp rating.

I don't see any prohibition in 394 for adding additional loads. If I can extend an existing K&T circuit, it stands to reason that I can add a load to it.
 

resistance

Senior Member
Location
WA
peter d said:
I don't see any prohibition in 394 for adding additional loads. If I can extend an existing K&T circuit, it stands to reason that I can add a load to it.

True! I meant to say, you cannot extend K&T (using K&T) to additional loads having a higher temp rating than the old 60 degree rated wire. **Most fixtures require a supply conductor to be rated @ 90 degrees.

Thanks Peter!

Why can't I bold print, and post in qoutes?
 
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