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David Naples

Expert Wire Electrical Services


Dangers of Knob & Tube Wiring

 Definition: Knob and Tube wiring is a method using knobs, tubes and flexible nonmetallic tubing for protection and support of single insulated conductors. - National Electrical Code (NEC)

Knob and Tube wiring typically dates between 1900 and 1950. At the time of installation it was “state-of-the-art”, but is now thought of as very dangerous. It is often a violation of current electrical codes and most insurance companies will not insure knob and tube wiring.

NEC article 394.10 describes the uses permitted to be in hallow spaces of  walls and ceilings or in unfinished areas of attics and roof spaces in only the following circumstances:

1.  For extensions of existing installations

2.  Elsewhere by special permission (from the Authority Having Jurisdiction) only

Uses Not permitted, among others includes, any hallow space where insulation is present.

Dangers of Knob and Tube Wiring


1) Knob and tube wiring utilizes a hot wire and a neutral wire only – No ground wire. Offering no protection whatsoever when a fault occurs. Fires and electrical shock can easily result from faults caused by knob and tube wiring.


2) Knob and tube wiring uses sheathing for insulation which will disintegrate easily over time.  Modern wiring uses much better insulation materials that are considerably safer.


3) Older electrical systems are often over fused. This allows more current to flow through the wire than it is meant to handle, leading to excessive heat and possible fire.


4) Older electrical systems were not designed to carry high ampacity loads, these extra loads lead to the insulation becoming brittle, exposing bare wire, which can cause fires.


5) Knob and tube wiring also uses two-prong receptacles, restricting the use of small kitchen appliances. With no ground wire, there is increased likelihood of shock and injury, especially around areas where water is common. Kitchens and bathrooms are especially hazardous.

...So What’s the responsible thing to do concerning Knob and Tube Wiring?

 At Expert Wire, We know that your home is not just some old house, it's special and worth preserving. That's why our technicians are trained to recognize potential hazards and offer professional recommendations. On knob and Tube wiring the insulation is generally too brittle to make any repairs to this wire. We are permitted to replace a device. When replacing an ungrounded two wire type receptacle we must follow the guidelines in the NEC article 406.4 (D) (2) (a-c).

 In general, the responsible repair to make is to replace the entire circuit. This is often a costly repair, but our concern is the safety of your home and the occupants thereof. Most insurance companies will not insure knob and tube wiring. This is another great reason to replace it, you can potentially save money and heartache by making the proper decision to replace the old out-of-date wiring.

Get an Expert Electrician in the Delaware & Maryland beach areas.

Ready to get the quality service you deserve? Contact Expert Wire Electrical Services today! At Expert Wire our primary goal is to bring you electrical safety and quality service with total satisfaction. Remember, leave the wiring to the Experts and have a powerful day!

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