Double Tap Connections on Breakers

Double Tap Connections on Breakers.  Reuben Saltzman is a second-generation home inspector with a passion for his work. Naturally, this blog is all about home inspections and home-related topics in the Twin Cities metro area. In addition to working at Structure Tech, he is also a licensed Truth-In-Sale of Housing Evaluator in Minneapolis, Saint Paul and several other cities.

Double tapped circuit breakers are one of the most common electrical defects that I find while doing home inspections in Minneapolis and Saint Paul, and they’re usually one of the easiest defects to correct.  Today I’ll explain what double tapping is, when it is and isn’t a problem, why it’s a problem, and how to correct this condition.

I didn’t consult with an attorney before writing this article, so I feel like I should add a disclaimer before giving any electrical how-to information:  Don’t do any of this work if you’re not qualified.  You could get electrocuted or start a fire.  This is only an overview.

Definition: When I say ‘double tap’, I’m actually not using the correct terminology; this is just what a lot of home inspectors say when two conductors are connected under one screw or terminal inside a panelboard.  There is no official term for this, so double tap works for me.  Sometimes this refers to two conductors at one circuit breaker, other times it refers to two conductors connected under one screw at the neutral bar.  Today I’ll be discussing two conductors connected to a single circuit breaker.

When it’s NOT a defect: Double tapped wiring is ok if the circuit breaker is designed for two conductors.  If a circuit breaker is designed for two conductors, it will say so right on the circuit breaker, and the terminal of the circuit breaker will be designed to hold two conductors in place.  The circuit breaker shown below is an older Square D designed to accept two conductors.  I highlighted and enlarged the portion of the label that says two conductors can be attached.  This is acceptable.  The only manufacturers  that make circuit breakers that are designed to hold two conductors are Square D and Cutler Hammer… but not all of their circuit breakers can be double tapped.

Here’s a newer type of Square D circuit breaker – instead of putting a bunch of text on the front of the circuit breaker, they now just have a little picture on the front of the breaker.

Electrical Basic Tips

Electrical Basic Tips.  ELECTRICAL Wiring codes and their origin

Wiring codes are intended to protect people from electrical shock and fire hazards .The very first electrical codes started in 1881 in New York to regulate the installations of electrical lighting. Since 1927 , the Canadian Standards Association also know as ( CSA ) has produced the (Canadian Safety Standards for Electrical Installations ) which became the basis for all provincial electrical codes.

The Canadian and the U.S. National standards differ occasionally in technical detail however they deal with the same physical phenomena and have similar objectives. As part of the North American Free Trade Agreement (NAFTA) program, U.S. and Canadian standards are slowly converging toward each other, in a process known as harmonization.

The difference between electrical insulators and conductors

In many materials, the electrons are tightly bound to the atoms. Wood, glass, plastic, ceramic, air, cotton — these are all examples of materials in which electrons stick with their atoms. Because the electrons don’t move, these materials can’t conduct electricity very well, if at all. These materials are electrical insulators..

Most metals, however, have electrons that can detach from their atoms and zip around. These are called free electrons . The loose electrons make it easy for electricity to flow through these materials, so they’re known as electrical conductors . They conduct electricity. The moving electrons transmit electrical energy from one point to another.

How circuit breakers/fuses work

Circuit breakers ( or the alternative , fuses ) may be one of the most important safety devices in your home. Whenever the wiring in your home or building has too much current flowing through it these devices cut the power until the problem can be fixed. Without these devices the potential for fires and other accidents resulting from simple wiring problems or equipment failures would be huge. The problem with fuses is they only work once . When you blow a fuse, it burns up the wire inside the fuse and you have to replace it with a new one. A circuit breaker on the other hand , closes the circuit when the current climbs to unsafe levels, but it can be reset and used over and over again.

GFCI ( Ground Fault Circuit Interrupter )

GFCI receptacles were designed to protect you from electrical shock. A GFCI monitors the amount of current flowing from the hot wire to the neutral wire. If the receptacle detects any imbalance in the current , it trips the circuit. They are designed to react as quickly as one-thirtieth of a second and can sense a mismatch as small as 5 milliamps. Building codes are now requiring that receptacles in potentially wet areas ( IE. Around bathroom/kitchen sinks or outside ) be GFCI protected for safety reasons. So let’s say you are outside with your power saw and it is raining. You are standing on the ground, and since the saw is wet there is a path from the hot wire inside the saw through you to the ground . If electricity flows from hot to the ground through you, it could be fatal. The GFCI can sense the imbalance in the current because not all of the current is flowing from hot to neutral as it expects — some of it is flowing through you to the ground. As soon as the GFCI senses that, it trips the circuit and cuts off the electricity.

Aluminium wiring

Aluminium wiring became popular in North America from the late 60’s to the mid 70’s due to the rising cost of copper. Aluminium wiring requires a lager conductor than copper due to the fact that it has greater resistance. For example , on a typical 15 amp circuit you would use a 14 gauge copper wire ( used for most lighting circuits ) where you would need a 12 gauge aluminium wire although local building codes may vary. Aluminium conductors were originally used with wiring devices intended for copper wires. This could cause defective connections unless the devices were designed to address problems in joining dissimilar metals.

Because of improper installation and design, some of the wiring junctions overheated under heavy current load and caused fires. Revised standards were designed to reduce these problems nonetheless aluminium wiring for residential applications has acquired a bad reputation and is no longer in use. Aluminium conductors are still used for power distribution and large feeder circuits, because they cost less than copper wiring, and weigh less, especially in the large sizes needed for heavy current loads. Aluminium conductors must be installed with compatible connectors.

Your Barrie Home inspector will check circuits in every room,  inspect your service entrance conductors and inspect the interior of your main panel board if new wiring has been added.

Aluminum Wiring Hazards and Solutions

Aluminum Wiring Hazards and Solutions.  Primarily in the 1960s and 1970s, many electrical contractors used aluminum wiring instead of copper wiring as a way to save money and lower construction costs. However, a number of electrical fires have been attributed to aluminum wiring. Many building codes have been rewritten to not allow the use of aluminum wire for branch circuit wiring in houses.

Copper vs. Aluminum — The Test Results are in! Tests have demonstrated aluminum wiring has inherent properties that make it more susceptible to fires when it was not installed correctly. Here are some of the problems with using aluminum wiring to conduct electricity. Aluminum does not conduct electricity as well as copper. An aluminum wire generates more heat. Aluminum is more brittle than copper. Wire is more likely to break or crimp if it is brittle. Arcing can occur if a wire breaks or crimps. This can cause very high temperatures inside the wall or ceiling Aluminum is more likely to corrode than copper. Aluminum will oxidize if it comes in contact with moisture. This oxidation removes the pure aluminum and makes the wire thinner. A thinner wire creates more heat when electrical current is running through it. Oxidation also causes the wire to expand, puts pressure on the protective plastic coating on the wire, and can cause the plastic to split. If any of these occur, arcing may result which can cause fires. Aluminum expands and contracts more than copper. This puts additional stress at all connections such as outlets and switches. If these become loose, arcing can occur at these points. If contemplating buying an older home with aluminum wiring or updating a home with aluminum wiring, contact a certified electrician to gain their expertise and opinion regarding the dangers of aluminum wiring.

State Farm believes the information contained in the Good Neighbor House is reliable and accurate. We cannot, however, guarantee the performance of all items demonstrated or described in all situations. Always consult an experienced contractor or other expert to determine the best application of these ideas or products in your home.
Between 1965 and 1973, aluminum wiring was used to install electrical branch circuits in about 1.5 million homes in the United States and Canada. Subsequent fires in some of these homes were attributed to faulty aluminum wire connections. During this period, studies conducted by the National Fire Protection Association, in conjunction with the U.S. Consumer Products Safety Commission, revealed that homes using aluminum wires manufactured before 1972 are 55 times more likely to have one or more electrical connections reach fire hazard condition than homes wired with copper. Aluminum wiring in itself is not dangerous. Aluminum wiring, when properly installed, can be just as safe as copper. But if it has not been installed properly, the connections-where the wires join to the outlets and switches- can present a fire hazard.

How to Tell The wiring that is of concern involves the circuit wiring to your outlets and light switches, and to appliances that us 115 volt current, such as furnace and washing machine. It is a single-strand, solid aluminum wire, silver in color as opposed to the characteristic copper wiring color. Most homes of any vintage employ some aluminum wiring. Often service entrance cables from the street that run to the distribution panel and major appliance circuits (220v) are aluminum. The safety concerns are not with the cables, but rather with branch circuit connections involving the lighting and other 115 v circuits. The Problem Most problems arise with solid aluminum wire, sizes #10 and #12 gauge. These problems concern the ends, or terminations, of the aluminum wire, where they connect under the bonding screws. If the connections are improperly installed, there is a potential for intermittent, hot connections where the wires join to the outlets and switches. Again, the problem is with the connections, and not with the wiring itself. The main difficulty with connections using aluminum wiring is a phenomenon known as cold creep. Aluminums coefficient of expansion (how much it expands when electrical current passes through it) is higher than coppers. Simply put, when aluminum wiring warms up, it expands more than copper does, and when it cools down, it contracts more than copper does. This expansion and contraction, over time, will allow for loosening at the connections. Also aluminum wire needs to be larger than copper to carry the same amount of electricity. Because the wires are thicker, you cannot get the same tightness at the connections. Therefore, they may loosen more quickly. To make the problem worse, all metals oxidize or corrode in an oxygen environment. Copper oxidation forms as a conductor, while aluminum develops as a resistor. This resistance causes heat. Oxidation accelerates when two unlike metals are in contact with each other. This may be part of the source of increased resistance when aluminum wire joins to outlets or switches intended for copper. Eventually the wire may start getting very hot, melt the insulation or fixture its attached to, and possibly even cause a fire. Evaluation of Your Electrical System As mentioned above, aluminum wiring can be just as safe as copper when properly installed. Denver’s Building Department has always maintained-including during the years 1965 to 1977, when aluminum wiring was being installed nationwide- a force of electrical inspectors who themselves are licensed electricians and have worked diligently to ensure that all installations comply with local and national standards. Many of the incidents publicized from other parts of the country simply don’t occur here. Still, any potential electrical problem is a potentially serious problem.

There are several warning signs to look for that would suggest the possibility of connection problems. They are:
– Sparks emanating from outlets
– Warm-to-touch cover plates on outlets and switches
– Smoke coming from outlets, junction boxes or switches
– Lights that flicker for no apparent reason
– Melted insulation (plastic) at the connections
– Smell of burning plastic at outlets
– Light bulbs that burn out quickly, or shine unusually bright
– Blown fuses or tripped breakers for no apparent reason
– The size of your television picture shrinks

Making Sure Its Safe
If you are experiencing one or more of the above connection problems, or are otherwise concerned, we suggest that you hire a licensed electrician to check over the wiring for the following:
1. Outlets and switches directly attached to aluminum wiring shall be listed for that purpose. The device will be stamped with AL/CU or CO/ALR. The latter supersedes the former, but both are safe. These fixtures are somewhat more expensive than the ordinary ones.
2. Wire should be properly connected (wrapped at least way around the screw in a clockwise direction). Connections should be tight. While repeated tightening of the screws can make the problem worse, during the inspection it would pay off to have the electrician snug up each connection.
3. Push-in terminals (terminals where the connecting wire is pushed into a slot rather than wound around a screw) are an extreme hazard with aluminum wire. Any connections using push-in terminals should be redone with the proper screw connections immediately.
4. There should be no signs of overheating darkened connections, melted insulation, or baked outlets or switches. Any such damage should be repaired.
5. Connections between aluminum and copper wire need to be handled specially. Current Denver City Ordinance requires that the connections used must be specially marked for connecting aluminum to copper. The National Electrical Code requires that the wire be a connected together using special crimp device, with antioxidant grease (see Repair Options, over).
6. National Electrical Code, Sections 110-114 and 310-314 address electrical conductors of dissimilar metals and prohibit the use of unlisted twist-on connectors for connection of copper and aluminum wiring.

A Final Caution The United States Fire Administration reports that annually, of the nearly 800,000 residential fire nationwide, approximately 75,000 began in the homes electrical distribution system that is, in the circuit wiring, receptacles, switches, cords and plugs. When a part of this network fails or is misused, a fire may result. Many of these fires were attributed to old technology aluminum branch circuit wiring. Of the fires involving old technology aluminum branch circuit wiring, 75 percent of the incidents involved receptacles, 12 percent involved panel equipment terminals, and 10 percent involved twist-on connections. Fire investigators, including those of the Denver Fire Departments Fire Prevention and Investigation Division, determined that old technology aluminum-wired receptacles and twist-on connectors, when used with aluminum wire, were failure prone, even when installed carefully in accordance with the manufacturers instructions. Leave aluminum wiring safety improvements to licensed electrical contractors. Denvor Building Department electrical inspectors will monitor work done under City permit. Any time you suspect unusual heat or smoke generated from the electrical system in your house, do not hesitate to call 911 and request a Fire Company to respond and evaluate conditions. The safety of your family is of primary importance.

This article by the Denver Fire Department is brought to you by Napoleon Home Inspections – The Barrie Home Inspector

The Barrie Home Inspector will open panel and junction boxes looking for concealed aluminum wiring.  Ensure you know what your buying before committing to purchase.

Inspecting Commercial Buildings and Their Power Supply

Inspecting Commercial Buildings and Their Power Supply

In electrical engineering, single-phase electric power refers to the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when loads are mostly lighting and heating, with few large electric motors. A single-phase supply connected to an alternating current electric motor does not produce a revolving magnetic field; single-phase motors need additional circuits for starting, and such motors are uncommon above 10 or 20 kW in rating.
In contrast, in a three-phase system, the currents in each conductor reach their peak instantaneous values sequentially, not simultaneously; in each cycle of the power frequency, first one, then the second, then the third current reaches its maximum value. The waveforms of the three supply conductors are offset from one another in time (delayed in phase) by one-third of their period.

Defining the Terms

Amps vs. Volts:
Think of electricity as water flowing through a pipe. The amperage is analogous to the amount of water flowing through the pipe. Amperage is also called current. Larger diameter wires can handle more current, just as larger pipes can handle more flow.

Voltage is analogous to pressure, the force which moves the water through the pipe. A small pump (low voltage) would produce less pressure than a big pump (high voltage).

In most buildings the voltage will either be 208 volt (low voltage) or 600 volt (high voltage). The critical question is how much voltage and amperage the system is rated at, or in other words, how much equipment can I use in the building?

208 Volt vs. 600 Volt:
Most modern buildings are equipped with 600 volt services. Equipment such as air conditioning units (over 5 tons), larger exhaust fans, electric heaters, and some lighting will utilize 600 volts. However, standard outlets and most lighting operate at 208 volts.

In North America, individual residences and small commercial buildings with services up to about 100 kV·A (417 amperes at 240 volts) will usually have three-wire single-phase distribution, often with only one customer per distribution transformer. In exceptional cases larger single-phase three-wire services can be provided, usually only in remote areas where poly-phase distribution is not available. In rural areas farmers who wish to use three-phase motors may install a phase converter if only a single-phase supply is available. Larger consumers such as large buildings, shopping centers, factories, office blocks, and multiple-unit apartment blocks will have three-phase service. In densely populated areas of cities, network power distribution is used with many customers and many supply transformers connected to provide hundreds or thousands of kV·A, a load concentrated over a few hundred square meters.

Buildings equipped with 600 volt services will always have a transformer to reduce the 600 volts to 208 volts for the main building panels. These transformers are generally located near the main electrical service entrance.

When comparing the amount of power available for different voltages, a 200 amp, 600 volt service has nearly three times the power of a 200 amp, 208 volt service.

This is of less importance. All 208 volt and 600 volt services are three phase. This means there are three power wires coming into the building.

Single phase services may be found in older, smaller buildings and are found exclusively in houses.

In some older buildings you can find a single phase and a three phase service. This is usually identifiable, on the outside, by two separate services leading to the building.

Determining Amperage of Service

When you are inspecting the electrical room, the two items of information you are looking for; the are amperage and voltage. The presence of a transformer in the electrical room is usually indicative that it is 600 volts. They do make transformers that can used to step up a 208 volt service to 600 volts, for a specific piece of equipment.

What you should typically see is a small conduit (high voltage, low current) going into the transformer and a larger conduit (low voltage, high current) coming out and leading to a breaker panel or a splitter panel.

The ratings on the switches and splitter panel are not to be relied on; they only tell you the maximum amount of current or voltage the equipment can handle. Do not rely on the rating of the hydro meter(s), for the same reason.

The best way to verify the amperage is to open the door of the main power switch and read the rating of the main fuses. This is sometimes impossible to do without turning the power off, but is always dangerous, unless you know what you are doing. Even with the power off, half the box is live. You can end your real estate career, right there in somebody’s electrical room.

Reading the gauge (size) of the main power wires (in the meter cabinet or main splitter panel) can also help to determine the amperage of the service. The gauge number is typically printed on the wire sheathing. Common wire gauge sizes, for copper conductors and the allowable amperages are as follows:

Wire Gauge Allowable Amperage
3 100 amps
000 200 amps
350MCM 300 amps
500MCM 400 amps