Is Knob and Tube Electrical Wiring Safe?

Do you live in a home built prior to 1950? Chances are the builder used knob and tube electrical wiring. Electricians no longer use the knob and tube method to wire houses, and it's widely believed to pose a hidden risk to homeowners. So, is knob and tube wiring safe or do you need to hire a professional to rip out and replace your existing system? Here, we explore the options.

History of knob and tube wiring

Knob and tube wiring was the go-to method for electricians in the United States from the 1880s to the late 1930s. Many pros continued to use this method through the 1950s, '60s and even '70s for new home construction.

Now, many homeowners looking to upgrade their electrical system or complete a renovation are discovering "hidden" knob and tube wiring in their homes and wondering how to proceed.

Knob and tube wiring gets its name from the ceramic knobs used to hold wires in place and ceramic tubes that act as protective casings for wires running through wall studs or floor joists. Instead of the three wires found in modern electrical installations, knob and tube wiring has only two — a black (hot) wire and a white (neutral) wire. This means there is no ground wire in the system for excess charge or in the event of a short.

As a result, outlets in a knob and tube home will have two prongs, not three. However, many electricians opt to install ground fault circuit interrupters (GFCI's) so there will be some three-pronged outlets. GFCIs can trip when they sense an imbalance between the hot and neutral wires. So even though they are not grounded, they are presumed safe because they can cut the electrical current when needed.

The hot and neutral wires in a knob and tube setup are run and sheathed separately and placed approximately one inch apart, rather than being bundled together as with new wiring. Most knob and tube installations are restricted to a 60-amp service.

Problems with knob and tube wiring

If a knob and tube system is intact and working, it poses no immediate risk to you and your family. Problems often arise, however, because of the age of the installation or modifications made to the electrical system by a previous owner or unscrupulous electrician. 

One of the most common problems with this kind of wiring is its insulation, which is made of rubber instead of plastic. Over time, the rubber degrades, exposing bare wires to air and moisture, in turn increasing the chance of a short or a fire.

Extra circuits are also a problem because basic knob and tube installations only allowed for 12 circuits in a home. Often, homeowners who needed extra circuits would pay contractors to add new circuits at the panel or simply splice into an existing wire. Both of these modifications run the risk of overloading the system.

You also need to watch for older homes with renovations. A popular electrical scam making the rounds involves attaching new wiring to a switch or socket, which is then checked by a home inspector who declares the house free of knob and tube wiring. In fact, the new wiring only runs the height of the wall and connects to knob and tube in the ceiling.

Building codes and insurance issues with knob and tube

The 2008 National Electric Code addressed some issues with knob and tube wiring, most notably its high heat dissipation that poses a fire hazard when combined with fiberglass insulation. As a result, the NEC now requires that knob and tube wiring not be in "hollow spaces of walls, ceilings and attics where such spaces are insulated by loose, rolled or foamed-in-place insulating material that envelops the conductors." 

It's important to note, however, that this code is not mandatory. States can choose to follow it at their own discretion.

Knob and tube wiring also poses a problem for insurance companies. Some demand higher premiums from customers with this kind of wiring in their homes, while other companies refuse to insure homeowners at all until the wiring is changed.

The final word....

If you want to replace knob and tube electrical wiring in your home, hire a professional electrician for the job. 

You'll also need to upgrade the service to your home to at least 100 amps, though many contractors will recommend 200-amp service to account for any future electrical needs. If wiring insulation has cracked and caused any fire damage, your costs will increase.

So is knob and tube wiring safe? Not exactly. The risk of faults and fires, coupled with the difficulty of finding home insurance makes replacement your best option.

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Smoke Alarms and CO2 Detectors: Battery or Hardwired?

Smoke alarms don't just save lives. They're also legally required in many parts of the country. Furthermore, newer homes might need to have hardwired smoke detectors. While hardwired smoke detectors still have a battery backup, they're connected directly to the house's main electrical system, meaning that, as long as you have power, they'll work even if you forget to change the batteries.

Battery vs. Hardwired

Homes built before 1992 generally aren't required to have hardwired smoke detectors. However, they still need to have smoke detectors installed, although battery-powered ones are adequate. Homes built in California after 1992 must have hardwired smoke detectors that also have a battery backup. This law also applies to homes built before 1992 that have been through major renovation projects.

Smoke Detector Locations

One smoke detector probably won't be enough to meet local ordinances, either. Generally, a dwelling needs smoke detectors outside of any area with bedrooms. If your house has two wings or has two floors with bedrooms, you'll need two smoke detectors. If the house was constructed after 1992, a smoke detector is required in each bedroom, and the smoke detectors must be hardwired.

Enforcement

When you own a house, you probably don't have to worry about a fire marshal coming into your home and inspecting it. However, when you sell your house, you will have to bring it into compliance with the laws for the number, location and installation type of smoke alarm. When you own a rental property or duplex, it's your responsibility to maintain operating smoke detectors that meet the law's requirements at all times.

Carbon Monoxide Detectors

Hardwired smoke detectors aren't enough, though. Since 2011, California homes that have anything that burns -- like a gas furnace, wood-burning fireplace, pellet stove or propane cooktop -- also need to have carbon monoxide detectors. The CO detectors need to be in any area with bedrooms and need to be hardwired in homes built after Jan. 1, 2011. Homes built before that date can have battery-powered detectors.

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Is it time to upgrade my electrical system?

Does Your Electrical System Need Updating?

The most important benefit of upgrading your electrical system is that your home will be protected from fire hazards caused by overloaded circuits. 

Don’t wait for sparks to fly; learn how to tell if your electric system needs an upgrade. 

Learn some good reasons why you may want to consider upgrading sooner, rather than later.

1. Should I update my electrical system?

Your home's electrical system is similar to your body’s circulatory system. Your electrical panel is the heart of your electrical system. The circuits that carry electricity to all the plugs, lights and appliances in your home are like your veins and arteries. Your panel determines how much power is available for the circuits to distribute to all the appliances, lights and outlets in your home.

The number and size of the circuit breakers determines how that power is distributed throughout your home. The first and most important step in updating your electrical system is to:

● Upgrade your panel (bringing more power from the utility to your home); or

● Replace the existing meter and circuit breaker box to allow it to handle more power; or

● Replace an electrical panel or circuit breakers that are obsolete, damaged or dangerous.

This doesn’t affect the wiring inside your home; it just gives your system the ability to have more power to distribute. The second part is to add additional circuits to distribute the power to your rooms and appliances. Updates also often include adding new electrical outlets and replacing the old receptacles.

Replacing an old circuit breaker box merits the expense — for a number of reasons.

2. Why should electrical panels in older homes be updated?

The most important reason to update your home’s electrical system is safety. When many older homes were built, they were designed with only 30, 50 or 60 amps for the entire home, using just a few circuits.

A circuit consists of all the outlets linked on one wire operated by a single fuse or circuit breaker. Circuit breakers protect your home by tripping and turning off when the wire running from your electrical panel to your appliances or devices becomes overloaded and in danger of becoming hot and catching fire.

Unfortunately, in many older electrical systems, the circuit breakers don't trip, even when the circuit is overloaded. Typically, a breaker will not trip due to a loose connection somewhere within the circuit.

Sometimes a homeowner gets tired of of the circuit breaker tripping, and unknowingly adds to the danger by replacing it with a larger circuit breaker than the wire is rated to carry.

To protect people from an overload, or the danger of electrocution and shock, safety devices such as ground fault circuit interrupters are now installed.

More power to you

3. How do you know if it's time to update your electrical panel?

Here are some symptoms that indicate your system is in need of an upgrade:

● Circuit breakers trip frequently.

● Your lights dim when you turn on other appliances.

● You have to use extension cords or adapters to create additional electric outlets for your home.

Circuit breaker panels have a life span of 25-40 years. If yours is older than that; if it’s in poor condition; or if it's old and has only a few circuits, and your breakers DO NOT trip … those can be danger signs as well.

Also: If you are adding high power-consumption appliances such as an air conditioner or a spa, it's likely that your system will need an upgrade to accommodate the additional demand.

Don't know if your home is grounded? Get a test.

4. What are the benefits of an upgraded home electrical system?

The most important benefit of upgrading your electrical system is that your home will be protected from fire hazards caused by overloaded circuits. You can sleep better knowing your home and family are protected. You will be able to use your modern appliances safely and your expensive electronic equipment will be protected.

Updating your electrical system also can increase your home’s resale value.

5. Can I upgrade my electrical system as a DIY project?

Electricity is not a good candidate for a DIY project. Amateur or DIY wiring is not only dangerous but can be far more costly to repair in the future.

Electrical work also is not an area where you'll benefit from hiring the cheapest provider.

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