Dolphines Electrical Contractors

Residential Wiring Best Practices

What is lurking within your walls? Part 2 of Series
Residential Wiring: Rewiring Options, Benefits and Drawbacks
PART TWO

In Part One I discussed k**b and tube wiring and the potential problems and issues that may arise if your home still contains legacy k**b and tube. Perhaps your home still contains k**b and tube? Or you are considering remodeling or planning new construction. In this article I will explain current options and residential wiring best practices. I will also explain the pros and cons for the two most popular wiring types, Romex and BX, and why I ALWAYS use BX in any new wiring I install myself, and insist it be used in any project in which I am managing or consulting.

Since the 1960’s, K**b and Tube has not met current electrical code thus any renovations or new construction built in the last 50 years should contain more modern wiring.

Today, residential construction primarily uses three types of wiring, Romex being the most common; followed by BX (also know as Armor Clad, or Flexible Metal Conduit); and individual conductors run inside conduit.

1) ROMEX: Romex is a composite cable consisting of 1 or more “hot” conductors, a neutral conductor, and a ground wire. All the conductors are individually insulated and the entire bundle is sheathed in PVC plastic to make a nice, neat package.
Romex is flexible, heat & fire resistant, easy to install, and relatively inexpensive.

Romex cable
Romex is by far the most common type of wire used in single-family residential applications today, and been used extensively for the past 40 years.

Romex has several advantages over k**b and tube. The wire is protected by 2 layers of insulation, with each individual conductor being insulated and the entire bundle also being insulated. This makes insulation failure a rare occurrence and reduces the risk of accidental electrocution and arcing. The plastic used is resistant to moisture and microbes, and is very durable. The plastic sheathing also has a very high melting point thus is heat and flame resistant. Splices are done in junction boxes, thus protected from the elements and pests. Plus all the wires needed for a circuit are right there together in one neat package.

One added benefit of Romex over k**b and tube is that k**b and tube emits fairly high levels of low frequency alternating current magnetic fields, due to the separation of the hot and neutral conductors. The magnetic field strength around k**b and tube carries a good distance from the wires, and is proportional to the distance between the hot and neutral conductors. Inside Romex cable, the hot and neutral conductors are side by side, thus Romex emits a much smaller, more localized and weaker magnetic field. The magnetic field strength drops very quickly with distance from the Romex cable.

2) BX: BX is also known as Armor Clad, or Flexible Metal Conduit cable. BX contains one or more individually insulated “hot” conductors, one individually insulated neutral conductor, and a ground wire, which may or may not be individually insulated.

BX is also known as Armor Clad, or Flexible Metal Conduit cable.
BX is sheathed in a flexible metal spiral made either from aluminum or galvanized steel. BX provides all the advantages of Romex plus some additional benefits.

The flexible metal sheathing is easy to install, about as easy as Romex. It resists puncture by nails and screws, and, as I will describe later, is more resistant to being chewed through by rodents and other pests than Romex and k**b and tube.

BX is as good as Romex from a Magnetic Field (MF) standpoint, but has the added benefit of shielding Electric Fields (EF). The metal sheathing absorbs the electric fields emitted by the wires and shunts it to ground. The plastic sheathing of Romex does not shield electric fields.

The main drawback is that BX is more expensive. It is about 35-40% more for the cable than BX. It is also slightly more difficult to install, as cutting the metal sheathing takes slightly more time, than cutting Romex.

3) Individual conductors run inside conduit: Individual conductors run inside conduit is used primarily in industrial and commercial applications, and is rarely used in residential wiring. It consists of individual, insulated conductors pulled from a spool through conduit, either metal or PVC. This is a more difficult and time consuming wiring method, but is more efficient in commercial applications where wiring runs must be exposed and thus must be inside some form of conduit. If the conduit used is PVC, the benefits are the same as Romex, low Magnetic Fields (MF) but no Electric Field (EF) shielding. If the conduit used is galvanized steel, the benefits are the same as BX, good resistance to puncture, low MF emittance, and good EF shielding.

Why I ALWAYS choose BX over Romex: A real world example.
Sometimes individual conductors run inside conduit is the only option, but when I have a choice between Romex and BX, I always choose BX. There are two main reasons:

1) BX shields electric fields. Many of my concerned clients have spent a lot of effort and money to shield against and reduce their exposure to electric fields. Some even go as far to turn off the circuits to their bedrooms when they sleep to reduce their exposure. If construction, remodels and renovations are done with BX, the electric field exposure is significantly reduced. The cost is greater, but for a 250 foot roll of BX, it is only about $30 more expensive than Romex. So for a small job the extra cost may only be $100 or so, and even for a large job the extra cost should not exceed $1,000.

2) Perhaps you are not concerned with electric fields. Here is another reason to use BX over Romex that can save you well over $1,000. BX is resistant to nails and screws and rodents and other pests. If you have to tear out a wall to replace a wire that has been punctured by a nail, supposing you were hanging a picture, this repair could cost well over $1,000. Here is a true story from when I worked as an electrician: I was working on a job where whenever the client switched on the recessed lights in the living room ceiling, the circuit breaker would trip. Diagnosing this problem required over 2 hours crawling around in an attic and isolating the area where there was a short circuit. I was frustrated to find TWO separate areas and narrowed down the area enough to open up the ceiling and see the problem. A rat, or other rodent, had completely chewed through the insulation of the Romex, allowing the hot and neutral wires to touch and create a short circuit. This had happened in TWO places in the living room ceiling!

When it’s Time for an Electrical Wiring Upgrade

The lights come on when you flip the switch, the TV works, and the refrigerator keeps food cold. That means the electrical wiring must be fine, right? Not necessarily. There may be times, especially if your house is more than 40 years old, when you need to upgrade electrical wiring for safety, or because the existing wiring no longer meets your family’s power needs. Rewiring can be a messy and expensive proposition, but with a little upfront planning you can minimize the disruptions and even turn the job into an opportunity to add features that will increase the valueofyourhome.

Safety issues with older wiring
Faulty wiring is the leading cause of residential fires, according to a 2009 study by the National Fire Prevention Association. And the older your house is, the greater the chances that the wiring might be outdated or unsafe.
Old wiring—even k**b and tube wiring that dates back to the early 20th century—isn’t inherently dangerous, but unless you were around when the house was built, you can’t be sure the electrical system is up to code. Plus, materials such as wire insulation can deteriorate over time.
If you don’t know when your wiring was last inspected, it’s worth paying a licensed electrician to give it a once-over, especially if you have any of these warning signs:
• Breakers that trip or fuses that blow repeatedly
• A tingling sensation when you touch an appliance
• Flickering or dimming lights
• A persistent burning smell from a room or appliance
• Warm, discolored, or sparking outlets or two-prong ungrounded outlets throughout the house
• No ground fault circuit interrupter (GFCI) outlets in kitchens, baths, and other areas exposed to moisture.
Another reason to consider upgrading is that some carriers refuse to insure houses with older wiring, or charge owners higher premiums.
Be on the lookout for aluminum wiring
Instead of the standard copper wire, many houses built in the 1960s and early 1970s have aluminum wiring, which is considered a safety hazard. “Aluminum wiring connections often loosen up over time,” says Greg Fletcher, a master electrician, educator, and author of several books on wiring. “That can cause overheating and possibly fires at receptacles when appliances are plugged in to them.” An inspection can determine whether it’s safe to leave the wiring in place. Sometimes the addition of copper connectors, called pigtails, at receptacles and circuit breakers can resolve potential problems.
When you need more power
Sixty amps used to be the standard for household power. Today, houses often need 200 amps to run air conditioners, flat-screen TVs, computer equipment, and all the other gadgets our parents and grandparents hardly imagined.
Not having enough power isn’t just an inconvenience; it can actually damage sensitive electronics. “It’s very hard on these devices if the voltage drops off,” says San Francisco-based builder Bob Hauser. Even with adequate power, you may need to add outlets to avoid relying on power strips and extension cords, an inconvenience and a potential safety hazard.
Prepare to open your walls—and your wallet
Upgrading electrical wiring is a big job, for one simple reason: All the wires are behind the walls. Every house is different and prices vary by market, but for a whole-house rewiring job, you’re easily looking at a bill of several thousand dollars. The vast majority of that is the labor involved to get to the wires, run new ones, connect them to every switch and outlet, close up the holes, and clean up the mess.
The easiest time to tackle this work is during a larger remodeling project, such as redoing a kitchen or building an addition, when contractors are knocking holes in the walls anyway. That speeds the process, which can take anywhere from five days to two weeks for an entire house, according to Lansdale, Pa., electrical contractor Wes Carver.
Depending on the circumstances, though, you might not need a top-to-bottom rewiring. Examples are when you need to add circuits to run a new appliance or power an addition like a swimming pool. In those situations, the expense and disruption could be reduced.

Plan ahead for future power needs
If you’re going to spend the money and cut holes in the walls, you might as well run all the wires you can. That way, you’ll be ready for any possible future power needs. “There are things to be bought and plugged into a receptacle 10 or 20 years from now that are not even invented yet,” says Fletcher.
One smart investment is structured wiring. These are heavy-duty data cables that enable the latest features of TVs, stereo equipment, computers, game consoles, phones, security systems—even Internet-based remote control of house systems like heating and lighting. While a standard electrical upgrade essentially maintains the value of your home, adding structured wiring can increase it. According to a 2009 study by the Consumer Electronics Association and the National Association of Home Builders Research Center, almost 50% of homes built in 2008 included structured wiring, a sure sign of its growing value to home owners.