Go Back  DoItYourself.com Community Forums > Electrical, AC & DC. Electronic Equipment and Computers > Electrical - AC & DC
Reload this Page >

My 1930's built house has modern elec panels but still use Knob and Tube wiring?

My 1930's built house has modern elec panels but still use Knob and Tube wiring?


Old 12-27-08, 12:24 PM
Thread Starter
Join Date: Feb 2006
Location: CA
Posts: 4
Received 0 Votes on 0 Posts
My 1930's built house has modern elec panels but still use Knob and Tube wiring?

I just discovered my 1930's house still uses ungrounded Knob and Tube wiring, after I tore down drywall to repair some water damage.

I always assumed it used a more modern grounded wiring system since all of the receptacles are 3-pronged and has modern main and sub electrical panels with breakers. Plus the house was remodeled several of times by previous owners.

I removed the wall plate from every receptacle to check, and just about every room use the Knob and Tube wiring with no ground wires with a 3 pronged outlet. Only the kitchen receptacles use Romex cables and grounded.

When I removed the plate from the electrical panels I can see 14/2 Romex cables connected to the breakers. So it appears whoever did the hack job pig tailed the Romex from the electrical panel to the Knob and Tube Wiring

Why would the previous owners do this? They went through the trouble to modernize the electrical panels and tore down the old walls and installed drywall, but left all of Knob and Tube wiring.
Old 12-27-08, 01:04 PM
Banned. Rule And/Or Policy Violation
Join Date: Dec 2007
Location: Chicago
Posts: 1,011
Received 0 Votes on 0 Posts
Likely, they did it to save money, in many jurisdictions you're not required to update knob and tube when you upgrade the service, in even in AHJs where this is required I frequently find the situation you are describing at home inspections in my area (Chicago) as a result of un-permitted work.

There are a number of issues related to knob and tube wiring, these include deteriorating insulation, ungrounded circuits, incorrect junctions between knob and tube and modern wiring, insufficient wiring gauge for the attached fuse or circuit breaker (for exactly the reason you encountered, someone sees 12 to Rome exit the panel and has no idea it's connected to concealed knob and tube knob and tube wiring somewhere downstream of the breaker) and so on.

Speaking just for myself, if I owned a property with energized knob and tube wiring and a modern electrical panel, and I was not going to completely rewire the knob and tube circuits, the first thing I would do is install AFCI breakers upstream of every circuit I suspected might include knob and tube segments.

Fortunately the GFCI protection afforded individuals does not depend on the presence of a a valid equipment ground, so GFCI protected receptacle outlets installed in increased risk locations (such as near sinks) will still protect individuals against ground faults, but this does not provide a ground, and for example some types of modern electrical equipment (such as many computers) require connection to a properly grounded outlet for the NEC and the manufacturers installation instructions.

One other issue to keep in mind: now that you're aware that you have knob and tube wiring installed you may be required to disclose this if the insurance company sends you a request for additional information about your property or if you change insurers, and many insurance companies at least in my area (Chicago) will not write or renew insurance on a property with any energized knob and tube wiring, and if a homeowner is aware of this condition and did not disclose it the insurance company might refuse to pay a claim for fire damage related to the presence of the knob and tube wiring.

All in all, it's a real headache...
Old 12-29-08, 09:53 AM
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,942
Received 44 Votes on 42 Posts
Originally Posted by garycoleman View Post
They went through the trouble to modernize the electrical panels and tore down the old walls and installed drywall, but left all of Knob and Tube wiring.
It would be illegal (against code) in most jurisdictions to leave K&T in place when the walls are open. Usually when the walls are opened up, that is considered a large enough remodel that the wiring, receptacle spacing and lighting would have to come up to code also. You also are not allowed to extend any K&T circuits, so if they did that using Romex is absolutely would have required replacement of the K&T. Basically the only thing you can do with K&T is leave it as-is. That even forbids placing any type of insulation over it.

You should also be aware that a circuit which has any K&T wiring should not exceed a 15A breaker.

If you treat this as a retrofit, you are allowed to install three-prong receptacles on K&T circuits as long as you have a GFCI receptacle as the first device or a GFCI breaker on the circuit. You should attach stickers to each receptacle faceplate which read "NO EQUIPMENT GROUND" and "GFCI PROTECTED OUTLET".
Old 12-29-08, 12:27 PM
ray2047's Avatar
Join Date: Mar 2006
Location: USA
Posts: 33,581
Received 13 Votes on 11 Posts
Do you have a large box with a cover screwed on near the breaker box. It is common practice in a retrofit to gut the original fuse box and use for a junction box. In that case the Romex you see may only run as far as the gutted fuse panel.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: