jar546
CBO
It is much easier than you think. No box needed?
-
Welcome to The Building Code Forum
Your premier resource for building code knowledge.
This forum remains free to the public thanks to the generous support of our Sawhorse Members and Corporate Sponsors. Their contributions help keep this community thriving and accessible.
Want enhanced access to expert discussions and exclusive features? Learn more about the benefits here.
Ready to upgrade? Log in and upgrade now.
How to Connect NM Cable (Romex) to Knob and Tube
- Thread starter jar546
- Start date
Yankee Chronicler
REGISTERED
Wire nuts are the key. It's all good if you use wire nuts.
steveray
SAWHORSE
But you have to make sure to get the right number of twists before you put the wire nut on......
jar546
CBO
Glad you caught that. Chris "Romex King" Kennedy text me that 21 seconds after I posted it.
TheCommish
SAWHORSE
That is wrong, the grounding conductor needs to be cut off
Commish, It appears the grounding wire is bent out of the way.
I think I prefer the connection in a junction box, realizing there is additional cost.
Is that #14ga ROMEX on a 15am fuse?
What gauge wire is the Knob-n-Tube, #12ga copper? Is it always assumed KNT is 12ga CU or does the inspector puts a wire gage on it?
I think I prefer the connection in a junction box, realizing there is additional cost.
Is that #14ga ROMEX on a 15am fuse?
What gauge wire is the Knob-n-Tube, #12ga copper? Is it always assumed KNT is 12ga CU or does the inspector puts a wire gage on it?
TheCommish
SAWHORSE
I see that it is bent out of the way, to complete the hack the ground has to be cut off so the when the N & T is upgraded to a current y allowed conductors they have to replace the existing romex
mark handler
SAWHORSE
All electrical connections shall to be enclosed and protected. Anywhere you have wires spliced together, you need an approved junction box.
Yikes
SAWHORSE
I know what a bad transition looks like, but I haven't seen many examples of what a good transition (from K&B to a box) looks like. Any photo examples?
jar546
CBO
Yep, It's just that simple.
mark handler
SAWHORSE
I do not see anything that allows that connector without a box/enclosure
steveray
SAWHORSE
334.40 Boxes and Fittings.
(A) Boxes of Insulating Material.
Nonmetallic outlet boxes shall be permitted as provided by 314.3.
(B) Devices of Insulating Material.
Self-contained switches, self-contained receptacles, and nonmetallic-sheathed cable interconnector devices of insulating material that are listed shall be permitted to be used without boxes in exposed cable wiring and for repair wiring in existing buildings where the cable is concealed. Openings in such devices shall form a close fit around the outer covering of the cable, and the device shall fully enclose the part of the cable from which any part of the covering has been removed. Where connections to conductors are by binding-screw terminals, there shall be available as many terminals as conductors.
wwhitney
REGISTERED
Per NEC 300.20(B), if the junction box shown is ferrous, you'd need to cut a slot between the entry holes of the individual conductors, or otherwise mitigate the potential for inductive heating of the ferrous box. [IIRC, the Canadian Electrical Code only requires this for conductors carrying 200A or more, as the 60 Hz inductive heating for a 15A or 20A branch circuit will be small.]
Cheers, Wayne
Cheers, Wayne
jar546
CBO
This is exactly how we did it when necessary and what I expected as an inspector when someone had to do the same. The preference is to replace the knob and tube but this was not always in the customer's budget. This is a safe method that has been used for many decades.
Mr. Inspector
SAWHORSE
All knob and tube wiring I saw always had an issue with the insulation falling off. Years ago, I was had a long metal pipe which touched the hot and neutral which ran on opposite sides of a basement. ZAP!
Yikes
SAWHORSE
What are the "bushings"? Are they just some kind of rubber washer or gasket?
jar546
CBO
Yikes
SAWHORSE
Thanks, but I assume those aren't available in the current retail market. I meant, what bushing would I buy today that would fit in the knockout hole on a typical electrical box? I assume the goal is to both protect the wire and generally fill most of the void created by the knockout.
steveray
SAWHORSE
Not enough free conductor length....
jar546
CBO
Nitpicker
steveray
SAWHORSE
Not like I said it needed air sealed boxes or anything...
N1102.4.6 (R402.4.6) Electrical and Communication Outlet Boxes (Air-Sealed Boxes)
Electrical and communication outlet boxes installed in the building thermal envelope shall be sealed to limit air leakage between conditioned and unconditioned spaces. Electrical and communication outlet boxes shall be tested in accordance with NEMA OS 4, Requirements for Air-Sealed Boxes for Electrical and Communication Applications, and shall have an air leakage rate of not greater than 2.0 cubic feet per minute (0.944 L/s) at a pressure differential of 1.57 psf (75 Pa). Electrical and communication outlet boxes shall be marked "NEMA OS 4" or "OS 4" in accordance with NEMA OS 4. Electrical and communication outlet boxes shall be installed per the manufacturer's instructions and with any supplied components required to achieve compliance with NEMA OS 4.