Introduction

Knob and tube wiring is a two wire, non-grounded wiring system that is supported by knobs where it attaches to framing members and runs through tubes where it penetrates framing. It was the main form of residential wiring until the early fifties, when “romex” wiring was introduced into the market.

There are two main types of knob and tube wiring. Early knob and tube systems (installed until around 1915) used a non-petroleum based insulation that tends to crumble when touched. The later versions used a petroleum-based insulation that holds up better but still degrades quickly when exposed to heat or weather.

Problems

Knob and tube wiring presents many problems, but the primary issue is that it does not have a ground wire. Grounding is very important, not only for personal safety, but also for the safety and longevity of modern appliances, including computers and other home electronics. A non-grounded circuit is a safety hazard when any device requiring a ground (having a 3-pronged cord) is plugged in to it. The National Electric Code does not permit a separate ground wire to be added to a knob and tube system, so that leaves little option but to rewire.

Another problem associated with knob and tube systems is that most do not have junction boxes for light fixtures. Instead, the wires are fed through a 1×6 board and connected directly to the light fixture. This makes the otherwise simple task of replacing an old light fixture with a modern unit not only difficult but unsafe.

A third frequent issue with knob and tube wiring is improper modifications. When knob and tube was originally installed the technique used to splice wires was solder and tape. To the layman it looks like the wires are simply twisted together and then taped and thus many do-it-yourselfers have done just that when making modifications to their home’s wiring. These types of improper connections can lead to arcing and eventually to a fire. Today’s code does not permit splicing the wires with solder and tape; instead, any splice should be made with wire nuts and enclosed in a junction box. Some jurisdictions do not permit adding-on to knob and tube circuits at all.

Finally, another issue that has become prevalent with knob and tube wiring is obtaining home insurance. Most insurance companies are very aware of the many issues associated with knob and tube wiring and have adjusted their policies accordingly. Some insurers will not sell a policy at all if the home has knob and tube; others will, but at an increased rate.

Knob and tube rewires

To many people a knob and tube rewire seems like a daunting task. Some contractors tell stories of having to cut slots in all the walls in order to get the new wiring in. Some say you will have to bring the entire house up to code as it relates to the number of receptacles, etc.

At Bowie Electric Service & Supplies, Inc., we approach knob and tube rewires with a different attitude, one developed from years of experience doing these rewires. We fish the new wiring in wherever possible using the latest tools, such as flexible drill bits and interconnecting fish rods. If we do need to cut a hole to get a wire in we use a hole-saw and we cut all holes the same size (making the patching much easier and therefore less expensive). Where a receptacle is very difficult to get to without damage our technicians may suggest a new location that requires little or no damage.

We work in occupied homes often and are comfortable doing so. We use tarps for protecting furniture and floors and special covers for our saws that collect the majority of the dust created when a cut becomes necessary. We have done hundreds of knob and tube rewires and our crews are well-qualified craftsmen.

If you have any questions or concerns about the knob and tube wiring in your home, please contact us for more information.

Zinsco brand panels, also known as just ‘Zinsco panels’, made by Sylvania, frequently pose safety and reliability risks.  We highly recommend their replacement if you still have them in your home or condominium.

Two-fold fire threat

Zinsco panels have always had a reputation for their breakers not tripping.  This means that an overloaded or faulty circuit which should be automatically shut-off by the breaker could be allowed to continue operating.  This is a serious fire hazard.
In addition, Zinsco breaker panels have been known to cause fires themselves.  The aluminum busing and the connection to it from the breakers is not very good and you will quite often find that there is overheating at that connection.  Circuits with larger and continual loads are frequently where the problems will show up.  These types of circuits include those with electric water heaters, electric heaters, and furnaces, as well as 120 volt receptacle circuits with portable heaters or other appliances plugged into them.

What to do if you have a Zinsco panel

Many insurance companies will not write insurance for and some banks will not finance homes with Zinsco panels.  Home inspectors usually will recommend the replacement of a Zinsco panel during purchase and sale inspections.

If you have a Zinsco panel in your home, please contact us for more information about having it replaced.

Welcome to the Bowie Electric company blog!

This is where you will find great articles covering a range of electrical topics, from current trends in the electrical contracting industry to answers to frequently asked electrical questions.

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