What is GFCI Protection, and Why Do I Need It?

David Sanders • June 15, 2022

The Complete Guide to Ground Faults and Ground-Fault Protection

Introduction

Of all the electrical hazards in our lives, ground faults are probably the most common but least understood. One out of every four American consumers do not know the purpose of their ground fault circuit interrupting devices (GFCI’s), nor that they can prevent electrical shock and electrocution[i]. This is a deep subject and can be technical, but its importance to safety cannot be overstated. The Consumer Product Safety Commission (CPSC) estimates 50 percent of home electrocutions have been prevented since the introduction of the GFCI,[ii] a device that automatically detects ground faults and breaks a faulted circuit. Before GFCI’s, nearly 800 people died each year from electrocutions in the home. But now, the household electrocution death rate is down to less than 200 a year.[iii]

We believe those numbers could drop even more with proper education. That is why we are taking the dangers of ground faults seriously and spreading the word about preventive measures and best practices. This article will help you understand, not only what electrical ground faults are, but what you can do to protect yourself and loved ones with ground fault circuit interrupting devices.

What is a Ground Fault?

The most common definition is “an unintentional electrical path between a power source and a grounded surface.”[iv] This seems easy enough to understand but is actually more technical than the average person realizes. For instance, what is a grounded surface? And we understand “unintentional” but would an intentional path ever be okay? (The short answer is, yes!)

Let’s break it down.

Anything “grounded” simply means it is connected electrically to the earth. A grounded surface, then, is an extension of the earth’s electrical potential. As such, any grounded surface should have the same electrical charge as the earth it is connected to. There should be no voltage between the two. Of course, nothing is ever quite perfect in the real world. Because of varying resistances and distances along a conductive path there may be a few millivolts up to several volts of difference between one of its locations and another. In most cases, the difference is too small to matter. Essentially, in the same way one end of a copper wire is electrically the same as its other end, something that is grounded should be one with the earth, electrically.

We said a ground fault is a “path,” which means electricity can travel on it. As in life, there are easy paths that are smooth, wide, and straight, and there are difficult paths that have obstructions; they are narrow and crowded, crooked, choked. You name it. Electricity may travel many paths, but not all paths are equal. Some paths “impede” or resist current flow more than others. And, just as gravity affects every path we walk on, all electrical paths resist current flow to some degree or another.

The term “ground fault” can be misleading. A ground fault may have little to do with the earth. Instead, its unintentional path may travel mainly through the system of bonding jumpers and grounding conductors back to the source, with only a small amount leaking through the ground. Because our electrical systems are grounded, these bonding paths are grounded surfaces.

Electricity will take all available paths to return to its source. You may have heard, “electricity just wants to go to ground,” or “electricity always takes the path of least resistance,” but neither statement is accurate. If there are a million paths, the current will be shared on all million at the same time. The amount of current an individual path contributes will depend on its own resistance, the total resistance (impedance) of all available paths, and the amount of voltage pushing the current through them.

Normal Current Flow is Intentional.

In trying to get a clear picture of what a ground fault is, it may be helpful to first understand how a normal electrical current path functions. Electrical current, measured in amperes (Amps), is the flow of electrons through a conductor. For electricity to do our bidding safely, we design “circuits” as the designated paths for currents to follow.

An Intentional Circuit:

begins at a specific electrical voltage source (a battery, a generator, or a transformer).
is protected close to its source by a breaker or fuse.
passes through a “load” (electrical utilization equipment such as a toaster or a desktop computer) in order to do a specific job.
Follows a planned route to return to its source. Electricity does not want to “go to ground,” but if it wants anything, it is to return to its source.

An important thing to keep in mind when discussing electrical safety and current flow is that, aside from static electric phenomena such as lightning strikes, for current to flow there must be a round-trip, complete path, to and from a source. If there is any break in the path, and if no other path is available, the flow of current will stop instantly.

We further ensure electrical safety and proper usage of electricity by using insulated conductors, and we take care to prevent electrical collisions (aka “short circuits”) by keeping all the different paths isolated from one another at connection points. If things proceed according to design, all is well. But in the case of a ground fault, electricity escapes its designated path and takes other paths back to its source. This may be only a small part of the electrical current veering from the path intended. To be a ground fault, it does not even need to be all of the current going astray, it is still potentially lethal.

What Does a Ground Fault Look Like?

We know how a proper circuit is supposed to behave; we know the safety measures of design to keep all intended paths separate and directed through a load and back to the source. But to understand the dangers of a ground fault, the next thing to realize is that the possibilities are endless. A ground fault can take any one unintended path, or it can spread out and take many.

A couple of key concepts to understanding how electrical current flows on a path are “resistance” and “impedance,” which sound like the same thing because they are related, but have an important difference. To explain, if voltage is the pressure pushing electrons through a conductor, then resistance is the property of that conductor which restricts the flow. Impedance is one level higher and describes the total resistance of all the different component resistances of an entire path; it is the total resistance to be overcome for current to flow in a circuit. Resistance will make one path easy and another path difficult, and in the case of parallel paths where multiple paths all share the current, resistance will also determine how much current each path will receive. Impedance will determine how much current flows through the entire path.

Bringing it back to safety, there are three main categories of hazards for a ground fault path to take: The Low-Impedance path, the dangerous High-Impedance path, and the very dangerous Open-Ended Hazard.

The Low-Impedance Path:

The first category of a ground fault scenario is our ideal, the Low-Impedance, or Bonded-Grounded path. It’s the next best thing apart from everything going right. When we intentionally bond all nearby non-current carrying metal parts together in a complete path back to the source, this becomes the emergency, back-door escape route that we want current to take, should something go wrong.

In any ground fault scenario, an unintentional path is created between a point in the circuit meant to carry current and its source. This could be a wire that has come loose from an intended connection point, such as from a terminal screw or wire nut. The hot conductor then contacts the metal casing of an enclosure such as an electrical box. It could be a section of a circuit that is damaged by a nail or rubbed raw by a vibrating metal duct. But, if all these parts are electrically bonded, our stray current can beat a hasty retreat back to its source, and Boom—a fuse blows or breaker trips, because it was a low impedance path and the rush of current was too high for the protective device to carry. This is good because the current stops instantly. Lives and property are saved. Such is the case of a properly-protected low-impedance path ground fault.

The High-Impedance Path:

While grounding an electrical system makes our electrical safety more consistent, it can also make the very earth beneath our feet more dangerous. The high-impedance ground fault uses a path that is too restricted to allow a high current through it. Generally, it will follow paths through the earth and other grounded surfaces that are not ideal conductors to reach the source. And with high impedance, we get low current. This means that a fuse or breaker may not be able to open the fault and save lives. So, if the fault is allowed to continue this way, a person could unwittingly step into connection points along the path and become another parallel path in the fault. This can be fatal and has claimed many unsuspecting victims because, when you are being shocked, you may not be able to get away from the electricity flowing through you.

The Open-Ended Hazard:

At this point in the scenario, there is a third hazard that exists as a subset of the other two. We have described what happens if there is a completed path from a voltage point back to the source. Whether it is a High-Impedance or Low-Impedance path, current will flow through it back to the source. The hazard of the Open-ended fault is that there is not a complete path...yet.

For example, sometimes a section of metal water pipe (which should be bonded to earth) needs to be replaced, but today plastic piping is often used as a replacement instead. This is fine as long as a bonding jumper is fastened in place on both ends to ensure the continuity between both parts of the metal piping system. If, for some reason the metal parts are not re-bonded with a jumper, or the bonding connection comes loose, there is no longer a complete path, and part of the piping system has just become an island, disconnected from the earth. If damage then occurs to a hot conductor and it makes contact with the orphaned section of metal piping nearby, electrical potential will simply extend out to the furthest part of the new conductor(s) and wait for a complete path to be made back to the source.

That opportunity could come along in the form of a person, unknowingly brushing up against an electrified surface while standing on the earth or some other grounded surface. At this point, a complete path would then be created, and the person would become the major link with current flowing through him or her to the ground and back to the source. This is a serious shock hazard that has killed many people. But ground fault dangers can be greatly mitigated with GFCI devices.

Why does electricity use the earth as a path?

Residential electrical systems, at least in the United States and Canada, are grounded in your service transformer (at the “neutral” or middle point in the secondary winding, to be exact). This is done by the utility company, and it is what makes your electrical system “grounded.” It simply means they have referenced the entire system to a common voltage point, the earth. Another way of looking at it is that the earth has been made to have the same electrical potential or voltage as the center point of the voltage source. The earth and the neutral point become unified, electrically.

With grounded systems, we are required to maintain (that is, to extend) the earth’s electrical potential in specific places. We drive ground rods at our Main Disconnects and bond all the non-current carrying metals in our systems to the earth there. This is also the only place where our neutrals and grounding conductors all get bonded together which keeps current from flowing on the grounding system in normal situations. What this does, in effect, is to make the surface you stand on roughly the same in potential as the neutral conductor in all your receptacles.

Because the earth is an extension of the neutral, it can become a ground-fault path. However, the National Electrical Code (NEC) states that the earth must not be considered an effective fault current path. This is because the earth’s resistance varies greatly depending on composition and conditions.

If current is impeded (restricted) enough, it will still flow but will be diminished to the point that, although still deadly, it may never rise to the level of tripping a breaker or blowing a fuse. And if part of the fault path travels through a person’s body they may be electrocuted. The fuse would never blow or breaker never trip, and the fault would continue until someone else finally turned off the circuit.

What is a GFCI?

A Ground fault circuit interrupting device (GFCI) protects us from shocks by breaking a circuit when an imbalance of current flow over time is detected. An “imbalance” means there is a different amount of current coming in on the circuit than there is going back, which would indicate a ground fault or electricity taking some other path than the one intended. GFCIs are sensitive enough to detect and open faulty circuits with imbalances of only 5 to 6 milliamps.

GFCI’s are required by UL standards to break circuits on a trip curve. That is, they open based on the intensity of current over time. This allows a smaller and less dangerous current leakage to last longer than a greater one, and reduces nuisance tripping while still providing adequate shock protection. For example, with a 6-milliamp current leakage, the GFCI has up to 6 seconds to break the ground fault, but with ground faults of 30 milliamps it would open in under 20 milliseconds – quick enough to keep most human hearts from going into ventricular fibrillation. Once the faulted circuit is broken, current stops flowing.

How does GFCI protection work?

GFCI’s use an ingeniously simple mechanism for detecting stray currents. They utilize a doughnut-shaped iron ring inductor called a toroidal coil to help contain magnetic fields.

Both the hot (supply) and neutral (return) legs of the circuit are coiled around the sides of the ring. Along with these, a secondary coil is used for a sensor that would naturally pick up induction through any magnetic fields created by current in the live circuit.

With this set-up, as long as the hot and neutral currents are equal, their magnetic fields cancel one another, and no current is induced into the sensor coil. If they become imbalanced, which would indicate a ground fault, a current is induced into the sensor which in turn activates a relay to open internal contacts in the receptacle, thus breaking the circuit and stopping current flow.

Can I still be shocked, even with a GFCI?

Yes, because GFCI’s only detect an imbalance in the circuit. If you complete a circuit by touching both the live hot and neutral components of a GFCI device, while being insulated from ground, a balanced current will flow through you. The GFCI will not trip. Also, if you touch the hot terminal screw on the line side of a GFCI, it will not trip. GFCI’s only monitor the currents flowing through their toroidal coil.

Where do I need a GFCI?

The National Electrical Code calls out many specific requirements for GFCI protection. The following requirements are a summary of the locations most common in a home setting.

Note: These requirements are taken from the NEC 2020 code cycle. Check with your local codes as they may differ significantly both in code cycle and addendums.

Ungrounded Receptacles – If you want to use a three-prong receptacle at a location where there is no equipment ground, the NEC does allow it if GFCI protection is used, and the receptacle is clearly and permanently labeled as having “no equipment ground.”
NEC 2020 Requirements for newly constructed Dwelling Units (all homes, apartments, etc. where people dwell):
Note: When measuring the distance from receptacles, it is the shortest path the supply cord of an appliance connected to the receptacle would follow without piercing a floor, wall, ceiling, or fixed barrier, or the shortest path without passing through a window.
All 125-volt through 250-volt receptacles in the following locations must have GFCI protection for personnel.
Bathrooms – all receptacles in dwelling unit bathrooms.
Garages and outbuildings – If it has a floor at or below grade level, and it is only used for storage, or as a work area or similar types of areas, it must be GFCI protected.
Outdoors – Any receptacle installed outdoors requires GFCI protection, unless it is a branch circuit dedicated to snow melting, deicing, or pipeline and vessel heating. But to qualify for the exception, even these must have GFPE (ground fault protection for equipment) of 6 to 50 milliamps to protect the equipment.
Crawl spaces – If the receptacle is in a space where the “floor” is at or below grade level, protect it with a GFCI.
Basements – In previous code cycles, this rule used to only require GFCI protection in unfinished areas of basements, but as of the 2020 NEC any 125- through 250-volt, single-phase receptacle in a basement needs GFCI protection. The ONLY exception allowed is for fire or burglar alarm system receptacles.
Kitchens – where serving the countertops.
Sinks – if the receptacle measures 6 feet from the inside edge of the bowl. This means, if the garbage disposal, trash compactor, dishwasher receptacles are located under the sink and a six-foot cord could plug in and reach to the inside edge of the sink, it must be GFCI protected. If the refrigerator receptacle is within that boundary, it also must be GFCI protected. But now, with the additional requirements for the 250V receptacles, even Electric Ranges or cooking appliances with their receptacles within the six foot must be GFCI protected.
Boathouses – all receptacles.
Bathtubs or shower stalls – within 6 feet of the outside edges. This rule is similar to the sink rule, but notice it is measured from the outside edge, not the inside.
Laundry areas – all receptacles located in an area where laundering is done, whether 125V (110) or 250V. This means not only the washing machine receptacle and other utility receptacles in the area, but also the dryer.
Sump Pumps [422.5(A)(6)] – all sump pumps, no matter where they are located must have Class A GFCI protection. Class A GFCI devices are required to trip at current imbalances between 4 and 5 milliamperes.
Dishwashers [422.5(A)(7)] – The 6-foot sink rule would normally cover this, because most dishwasher receptacles are located beneath the sink, often on the same circuit as the garbage disposal. With this rule, it no longer matters where the receptacle is located. All dishwashers with 150V or less to ground and 60A or less must be protected with a Class A GFCI device.
There are also GFCI requirements specific for situations regarding permanently installed swimming pools, hot tubs and spas. It is best to use an electrician especially knowledgeable for electrical installations in these areas.
Anywhere you want to feel safer. The general rule is if it is anywhere near water or in a damp location, it is a good idea to have GFCI protection, whether it is specifically required or not.

What options are available for GFCI’s?

You can get GFCI’s as receptacles and breakers. There are also portable versions such as manufactured GFCI assemblies on extension cords and special plug assemblies on the utility cords of certain appliances and equipment.

In receptacle form, there are optional features to consider; some of them are required. Here’s a list of significant options for GFCI receptacles in and around the home:

1. Tamper Resistance – Most receptacles in the home are now required to resist attempts to get at their slotted entries with anything other than a two- or three-pronged plug. The design uses a blocking mechanism that prevents entry at single slots. This keeps children from pushing objects (keys, nail files, screw drivers, etc.) into one slot or the other of the receptacle.

2. Pilot Light – a highly visible LED light indicates the receptacle has power in most lighting conditions. These are popular in commercial kitchens where all receptacles must be GFCI protected. However, they are useful as well in dark corners of basements and other dimly lit areas where a strong visual cue from a distance would be convenient.

3. Self-Testing – As we discuss below, testing GFCI’s should be done at least monthly. The self-testing feature will do the task for you continually. Its green LED light turns red when something is wrong. This is a widely available feature; just look for the words “Self-testing” on the packaging.

4. Weather-Resistance – If you are installing an outdoor receptacle that needs GFCI protection, make sure to use a weather-resistant GFCI. They are required along with “in-use” covers that provide physical protection from inclement weather, even when a cord is plugged into them.

5. Audible warning– In specific locations such as for basement sump pumps and freezers, this is a great option to look for in your GFCI. It will sound an audible alarm when it has tripped.

Note: While an audible alarm might suffice if you are at home, we found at least one company with an app and smart plug adapter solution. It sends notifications to your cell phone or email should the power go out on a circuit. As smart technology and products develop, we expect built-in network connectivity in the near future as an option for smart GFCI receptacles and breakers. Disclaimer: We have neither tested, nor are affiliated with the GFI Notify brand and receive no benefit for listing it as a possible solution.

Testing your GFCI’s is just as important as installing them.

As with any lifesaving equipment, regular testing is necessary. And it makes sense, after going to all the trouble of installing ground fault protective devices. Checking them frequently to make sure they are still capable of performing their function guards the investment.

Read the manufacturer’s instructions and you will find a regimen for pressing the test button, usually once a month. The test simulates a ground fault by cutting a resistor into half of the circuit. A receptacle in good working condition should trip off. To reset the device, press the reset button in far enough until a click is heard. This might require a little more pressure and depth than you would expect. A screwdriver usually works better than a fingernail.

Summary:

· For current to flow in a circuit there must be a round-trip, complete path, to and from a source.

· If there is any break in an electrical path, and if no other path is available, the flow of current stops instantly.

· A ground fault is an unintentional electrical path between a power source and one of its remote voltage points, usually through grounded surfaces.

· A grounded surface is an extension of the earth’s electrical potential.

· Normal current flow is intentional; it follows a planned route to return to its source.

· GFCIs save lives; since their introduction, electrical deaths have been reduced by at least 75% and home electrocutions have been cut in half.

· GFCI protection is required for many outlets in dwellings.

· GFCI’s, along with all lifesaving equipment, should be tested at least once a month.

[i] https://www.nickleelectrical.com/safety/electrical-safety-statistics

[ii]50 percent of home electrocutions have been prevented since GFCI’s

[iii] nearly 800 people died each year from electrocutions in the home. Now, it is less than 200 annual deaths.

[iv] https://www.cpsc.gov/s3fs-public/099_0.pdf

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Everything You Should Know About Knob and Tube Wiring

By David Sanders • May 5, 2022

If you own an older home with Knob and Tube wiring or are considering an option to purchase one, you may have wondered how safe the wiring is and whether you should investigate options for getting it fixed. Then, if you’ve begun researching on your own, you could be running across conflicting information about Knob and Tube, both in costs and required treatment, and even in the relative safety of the system in general. How do you decide what to trust? Considering the importance of your peace of mind and the safety of your family, the following statement cannot be stressed enough: Nothing beats a qualified and licensed electrician’s in-depth assessment of your specific situation. This is especially vital with Knob and Tube wiring. The above warning being said, this article will help you make an informed initial assessment about your wiring by explaining the important things everyone should know about Knob and Tube. Knob and Tube, 101 Knob and Tube wiring was the first standardized wiring method used in the United States. It dates back to the late 1880s and early 1900s when homes were first built with installed wiring or were upgraded from the existing technology of the day for lighting and heat. Knob and Tube was the main wiring method used in homes until 1925 when other options became more affordable. Some homes built as late as 1940 were originally wired using the Knob and Tube method. Knob and Tube wiring looks just like its name implies. Two single-conductor cables, insulated with a natural rubber coating, are run in separate lines – one for hot, the other neutral – through a support system of ceramic knobs and tubes throughout the structure of the house. The two lines are generally kept about a foot apart, and installed in open spaces in attic rafters, floor and ceiling joists, and voids within walls. The knobs secure and support the wires so they maintain an air space between themselves and the surrounding wood framing. The tubes protect the insulation of the conductors from contacting surfaces when passing through them. The method also uses flexible sleeves to add further protection where conductors cross one another or pass by obstacles in their path. In many homes, electrical boxes were not used at all. Receptacles and light fixtures were fastened directly into wall finish and framing, with the knob and tube wiring feeding them from within ceiling and wall cavities. When splicing was necessary, installers twisted the bared ends securely, then soldered the joint, applied tar, and made several wraps with a cloth-backed adhesive tape for insulation. These splices could be made anywhere in the line and were not required to be put in accessible protective boxes like we do today. Knob and Tube, Pros and Cons One positive about existing Knob and Tube wiring is it usually looks very neat when unmodified. The pride and workmanship of the installers from that era is apparent. They liked keeping their lines straight in parallel rows and were careful to drive the nail cores of their porcelain knobs straight. This was open wiring they knew would be visible to anyone who looked, at least in spaces like attics and floor joists above basements. Also, the original installation method, with its sleeves, tubes, and knobs, was good at protecting the wiring. In its time, Knob and Tube was state of the art. Over the years, these installations have either weathered the test of time, standing as monuments to the past, or they’ve been replaced, improperly modified, or burned down. That leads to the present dilemma faced by homeowners and insurance companies. Is the wiring still safe, even if it has lasted until now? It can be difficult finding insurance for a Knob and Tube wired home. Many insurance companies will not offer a policy without a signed agreement to have the wiring replaced within 30 to 60 days. For those willing to ensure existing systems, there are usually further safeguards required , such as a certified inspection by a licensed electrician, assuring the wiring is safe and intact. The certification usually needs to be filed with the local building department. Physics is Against Knob and Tube Why would most insurance companies see Knob and Tube as too great a risk? Besides a poor track record, there are several problems with its design that has left it with a bad reputation. The first issue that jumps to most peoples’ minds is Knob and Tube is a non-grounded wiring method. By code, electricians can’t install modern three-prong receptacles without that third wire dedicated to equipment grounding, unless ground fault circuit interrupting devices are installed. So, while not having an equipment grounding conductor isn’t great, that really isn’t the main problem. The biggest issue Knob and Tube faces is a simple little thing called HEAT . All wiring must deal with heat in one way or another. Wiring usually must be installed in warmer areas, like attics, where ambient temperatures can range much higher than in the rest of the house. And wiring itself creates heat, as I’ll explain further on. But Knob and Tube especially falls short in this area for two main reasons: Inferior materials and electrical Physics. Inferior Materials Knob and Tube wiring has not aged well. Back in the day, manufacturers used a natural rubber coating to insulate conductors. Rubber, which oxidizes and cracks when exposed to heat, was used until plastics became more available and affordable, around 1925, and even then, the newer insulation still did not meet today’s standards. The aged insulation of Knob and Tube conductors often falls off in brittle chunks when touched. Insulation is very important for rating a conductor’s ampacity (capacity for carrying current without harming the insulation). For example, the original 1897 NEC standards rated the ampacity of a Rubber coated copper wire of 14-gauge at only 12 Amps. Compare that with our lowest rated building wire today, a 14-gauge copper wire with TW insulation, rated at 15 Amps. It would be a mistake to treat Knob and Tube wiring as if it will handle the same amount of current as today’s wiring, and yet the mistake is made continually. Electro-Physics, Just Another Fatal Problem for Knob and Tube Electricians are familiar with the crumbly nature of Knob and Tube insulation and know how challenging it can be to make it safe. But regardless of the material that was used, there’s an even greater problem in the way the wiring method was designed to be laid out. When electrical current passes through a conductor, two things happen. First, electrical current naturally generates heat from within a conductor at the atomic level. Since heat is cumulative, this adds up with the ambient temperature surrounding the conductors to cause more stress on its insulation. The hotter a conductor becomes, the worse it becomes at conducting electricity. So, heat, no matter where it comes from, is a bad deal for electrical wiring in general, but especially for any method with poor insulation to begin with. The second effect of electrical current through a conductor is the generation of an electromagnetic field around the conductor . This is an amazingly good principle that we harness in everyday applications such as transformers, motors, solenoids, and inductive heating. But the principle can play havoc with energy efficiency if our wiring is doing any of those things, unbidden, in places we do not wish. An uncanceled magnetic field causes every piece of ferro-magnetic metal (such as iron) within the influence of that field to begin heating up. In modern wiring methods, such as non-metallic cable (A.K.A., Romex®), the electromagnetic effect brilliantly cancels itself out by way of being a balanced circuit. Every circuit should have an equal amount of current going to and from a load, so one magnetic field is canceled by its opposing field in the conductor next to it. That is key: the two conductors must be within each other’s magnetic field. Qualified electricians know how important it is to balance the current in our cabling and other wiring methods, and we know how to do it well. But, not so with Knob and Tube! The entire design of keeping a circuit’s conductors separated so far apart in framing spaces makes electromagnetic balancing impossible. Each single conductor without its canceling partner nearby is forced to do much unnecessary work – magnetizing and heating every nail and staple it passes next to – in order to simply do its job of carrying current. One very likely scenario deserves mention here. Existing Knob and Tube, although never energy efficient, may still be safe if the entire wiring system has been left intact in its original form and hasn’t been moved around or modified. This includes not only the wiring but the original fuse sizing as well. However, over the years, most systems have been modified in one way or another. Although the NEC, since its first edition in 1897 , has required all new Knob and Tube installations to maintain spacing of at least an inch between its conductors and other surfaces, this hasn’t prevented later encroachments on the rule. It can be something as innocent as blown-in insulation surrounding the conductors. The required airspace is gone, the conductors with their rubber insulation have no way to dissipate heat. Sometimes other systems, such as ductwork and piping have been installed too close to open Knob and Tube conductors. This happens more often than anyone would guess, and it can be a deadly mix. Remember, the uncanceled electromagnetic field surrounding a single conductor will induce heat into a nearby metal pipe or duct. And if the conductor accidentally makes contact with one of these metal surfaces in one place, the rubber insulation can heat up enough to be burned completely off. In such situations, a duct or pipe would likely become energized. This could lead to electrical shock but may also cause sparking which could start fires if it sets off combustible materials. Knob and Tube Installers could not Foresee the Future In the early days of home wiring, electrical consumption was much lower than it is today. When Knob and Tube systems were being designed and installed, they could not have foreseen all the requirements we would ask of our electrical systems today. Most electrical utility services for Knob and Tube installations are limited to 60 Amps. By today’s rules, the minimum requirement for a service is 100 Amps, with many new installations opting for twice that much to provide for future expansion. Compounding the heat problem, Knob and Tube circuits are fewer in number than their modern counterparts. Having fewer circuits means modern users end up having to play musical receptacles with their appliances, plugging in elsewhere to allow one circuit a chance to cool off. Circuits tend to be overloaded often, which warms the tired insulation evermore. Modern Household Wiring Methods, Pros and Cons In the United States, most locales allow non-metallic cable (Romex®) to be used in wood-framed residences. NM cabling and other modern methods are superior to Knob and Tube both in material and design in the following ways: The most common conductors used in modern house wiring are insulated with thermoplastic (for example, THHN – a thermoplastic insulation with a nylon coating that can handle at least 30°C (86°F) more heat than [SB7] rubber). Thermoplastic lasts exponentially longer than natural rubber and can handle more heat over time. If it does begin to overheat, thermoplastic softens and melts but is less likely to burn. When cool again, it tends to shrink back into shape and retains its original flexibility. Overall, thermoplastic does its job well and protects individual conductors from leaking current, which allows conductors to be run together in the same cable or conduit. Better insulation means a conductor’s ampacity (capacity for carrying current without harming the insulation) can be rated higher. Compare a 14-gauge copper wire insulated with today’s THHN with the Rubber coated 14-gauge copper wire from 1897. Today’s version can handle 15 Amps easily and can even be rated as high as 25 Amps in the right conditions and application (say, for a motor circuit or HVAC) Non-metallic cable, like all other building-wire cables, carries an equipment grounding conductor. All modern household circuits are purposely grounded in compliance with the latest code standards. Modern manufactured cabling keeps all of a circuit’s conductors within the electromagnetic field of one another, allowing for correct balancing. This cancels unwanted induced-current into other nearby metals. More branch circuits are used which helps to spread load current across the wiring better, keeping it cooler. One drawback with modern NM wiring is it can be rather ugly. Installers often get in a hurry and do not make their runs look neat or orderly as with the old Knob and Tube method. This really depends on the installers, though. Wiring with modern cables can still be done neatly and smartly, with proper airspace maintained for cooling. Note: Neatness and longevity design should be selling points a good electrical contractor can use to showcase attentiveness to heat reduction and energy efficiency. You might ask to see pictures of their finished wiring projects. Watch out especially for too many cables bundled tightly together, a practice that would reduce air flow and prevent dissipation of heat. Options for Fixing Knob and Tube Issues At this point, most of us will agree, Knob and Tube is something better to face now rather than later. We’ve talked about reasons to have wiring professionally inspected. So, let’s discuss what choices a homeowner has for dealing with Knob and Tube wiring that has seen the end of its lifespan in terms of safety. Essentially, there are two options. You can do a complete removal and bring in all new wiring, or you can leave intact the parts of the Knob and Tube system that cannot be easily reached, while splicing to it with new branch circuits and wiring. The NEC allows for both approaches and is very particular about the guidelines for doing so. Local building codes and insurance companies may have more stringent demands. Ideally, it is usually best to remove Knob and Tube completely and rewire the entire house. This offers the best peace of mind if it can fit in your budget. If you decide to go this route, new wiring will be grounded. More branch circuits can be added as well to split up demand load over many circuits rather than the few originals. Everything will be brought up to code at the same time, with three-pronged, tamper-resistant receptacles, GFCI and AFCI protection throughout the home, and special required circuits attended to. A licensed electrician will be able to explain code minimums, in terms of number and placement of receptacles and other circuit needs. You may also want to upgrade your service and load centers. If you have existing fuse boxes, they can be replaced with updated breaker box load centers. Electricians can often fish new wiring to existing receptacle and lighting locations. They will add remodel boxes where needed and will remove old wiring wherever possible. Wherever possible, qualified electricians will try to remove all traces of the old Knob and Tube conductors once they’ve been cut out, but will always, at minimum, ensure that power cannot be tied back into them later by accident. Sometimes fishing wires will not be possible without cutting into the walls, usually at the tops or bottoms, and, if fire-blocking is encountered, above and below cross members in the middles of walls in order to run the new wiring through. The holes in the walls will need to be patched professionally and then refinished. Talk with your contractors beforehand to decide who will be responsible for these repairs. There are situations where it may make sense to allow some of the Knob and Tube wiring to remain. In spite of the age of some well-maintained homes, they remain attractive due to their period charm or exquisite and often irreplaceable finish work. For example, an electrician may be dealing with a full upgrade and, in coordination with the homeowner, may choose to leave a three-way switching circuit intact. The circuit may have been installed in a pristine wall from the second floor to the main floor around a beautiful staircase and may be impossible to fish with new wiring to the existing switch locations without cutting into the walls. You may have an historic home or simply one you feel needs special care. It’s okay to ask your electrical contractors about their plans for fishing new wiring without destroying your home in the process. If the option to remove only accessible portions of the wiring is made, electricians will pull new, grounded branch circuit wiring from the load center only to the last few inches of accessible Knob and Tube wiring for each existing circuit. New junction boxes will be mounted, and each Knob and Tube conductor will enter the box through its own bushed hole. The new branch circuit wiring will also be brought into the box through a separate hole, and splices will be made between the two systems. The electricians will need to take particular care with cracked wiring to keep its exposed insulation as intact as possible. They may use 600-volt rated tape or shrink tubing to accomplish this. If a metal box is used, it will be bonded with the grounding conductor, but the existing wiring that remains will not be connected to the grounding system and will remain ungrounded. Note: It is also important to realize that not all electrical contractors are specialized in dealing properly with Knob and Tube wiring, so if you plan to leave any portion intact, you will want to carefully discuss this with your electrician. Additional Considerations when Upgrading If you research online, you will find quite a range of projected costs for upgrading from Knob and Tube. Some sites suggest $4,000 to $8,000, while others suggest anywhere from $5,000 to $40,000. These conflicting projections are based on location and scale, but the differences might also simply be from having been posted at different periods in which costs changed dramatically. Labor costs will vary by locale, but with today’s material pricing, the lower ends mentioned elsewhere online of $4,000 would barely cover the materials for even the smallest of homes. But rest assured, though price ranges will vary, trustworthy contractors will have thorough discussions with you before pricing a project. They will know the right questions to ask to narrow down the needs of your specific situation, and then should offer up-front pricing options so you can be fully armed to make the best decision for yourself and your family. For efficiency, it is usually wise to combine as many upgrades at one time as possible. Consider not only upgrading the wiring, but the service and electrical panels as well. GFCI and AFCI protection is advised, as well as additional branch circuits to split up loading, and these can all be figured in and planned together with the rest of the work to make the entire project run as efficiently as possible. It is always best to make these decisions at the beginning and to stick to them, rather than adding random changes as the project progresses. Of course, each project will be different. Variables come into play, such as how accessible the circuits are, and the conditional methods a contractor is expected to use in maintaining existing finishes. Leaving parts of the existing Knob and Tube may cut down on costs a little, though the requirements for boxing and splicing do add up in labor time and materials. On the bright side, a good thing to remember is that replacing Knob and Tube wiring is in everyone’s best interest, including the lender on your mortgage. Look into options for financing an upgrade to new and safer wiring. Shop around. Sometimes your electrical contractor will even have a system in place to offer a payment plan and costs can be spread out over time. These plans often offer up to a six month grace period before accruing interest. Summary If you’ve made it this far in the article, congratulations! You are now armed with the important aspects of Knob and Tube you need to make informed decisions about your wiring. Key things to remember are: If you have concerns about your Knob and Tube wiring (or any other electrical issues), it is always best to get a qualified and licensed electrician’s in-depth inspection. Knob and Tube was a very difficult wiring method to maintain due to its design requirements for spacing and low tolerance for heat. Rubber coated copper does not have the same ampacity as today’s wiring and must not be treated as if it does. The NEC makes allowances for circuits that are not able to be removed during an upgrade. A qualified, licensed electrical contractor can give you the best appraisal of your existing system and best options and costs for upgrading. Consider combining upgrades to get the most efficient return on your investment. Ask your financial institution and electrical contractor about financing options. You should be able to spread the costs out over time. https://www.facebook.com/Electrician-ED-107527198489309