Safety Tips, Videos and Links to Help You Select and Use A Manual Transfer Switch





Common practice of “backfeeding�?puts utility workers and homeowners at risk


Transfer switches required for safety under National Electrical Code®

Rosslyn, Va. (Date, 2010) �?Electrical Safety Foundation International (ESFI) is warning homeowners about the dangers of improperly installing and operating portable generators when spring and summer storms cause power outages. Hundreds of thousands of generators are used in the U.S. every year, especially before or during thunderstorms that cause massive power outages.


“This is the time of year when a majority of people rely on portable generators for their homes, and many times, they’re putting themselves at risk by not installing or using the generator properly,�?said Brett Brenner, President of ESFI. “People are in such a hurry to keep the lights and television on, the refrigerator running, or the basement’s sump pump operating, they don’t think about the potentially devastating consequences of hooking up a generator incorrectly. They put themselves, their families, their neighbors and utility workers at great risk of shock or electrocution.�?

According to Brenner, a common practice called “backfeeding�?is frequently used by untrained homeowners to give their homes power during an outage. Backfeeding occurs when a generator is plugged directly into a home’s electrical system, bypassing any built-in protection devices. The Occupational Safety and Health Administration (OSHA) warns that electrical power from a generator back fed through a meter into a utility system can cause fires and/or serious injury or death to utility workers working in the street or electricians working on nearby properties�?electrical systems.


Brenner said a solution to this potential problem is a device called a transfer switch, but many people don’t know it exists and is actually required. The National Electrical Code® (NEC®), which sets national standards intended to minimize the possibility and effects of fire and other risks, has required transfer switches be used with all portable generators in homes since 2002.
“Requiring transfer switches not only keeps homeowners safe, but it also saves them money,�?said Brenner. “If homeowners don’t follow code regulations, they could face fines in some municipalities. Having a transfer switch hooked up with their generator really is in the homeowner’s best interest in more ways than one.�?

Some transfer switches are specifically designed to connect a portable generator to a home’s circuit breaker panel, allowing homeowners to supply power safely to refrigerator, furnace, sump pump, and well pump circuits among others. During a power outage, a connected transfer switch prevents the utility power and the generator power from being on at the same time, eliminating another dangerous situation. The meeting of the two power sources can cause an explosive-like event in the electrical wiring that may result in both personal injury to those close to the event and a subsequent electrical fire.

For more information on generator and transfer switch safety, visit

The Electrical Safety Foundation International (ESFI) is North America’s only non-profit organization dedicated to promoting electrical safety in the home, school and workplace. ESFI sponsors National Electrical Safety Month each May, and engages in public education campaigns to help reduce property damage, personal injury and death due to electrical accidents.

Welcome: Guide




The information contained in this site is designed to educate homeowners on the importance and benefits of transfer switches �?home safety devices that restore the home’s power during utility outages by “switching�?to backup power from automatic standby systems or portable generators.  Transfer switches allow homeowners to safely maintain the home’s power supply while also alleviating the dangers associated with improperly installing and operating portable generators.  This site will help homeowners select and utilize the appropriate transfer switch for their home, as well as provide portable generator safety tips.

The transfer switch information on this site pertains to a common configuration in the home that consists of a 4-wire 125/250 VAC (two line conductors, one neutral, one ground), the normal source of supply being a power utility, the alternate source of supply being an on-site generator used for optional standby power, and the house loads being connected to a circuit breaker panel. 
This is certainly not the only configuration; however, it is the most common.

Look for the UL Mark on a Product


Since its formation in 1894, Underwriters Laboratories Inc. (UL) has earned the reputation as the leader in product safety testing and certification. The UL symbol has become one of the most recognized conformity assessment marks in the world.

A product certified by a third party such as Underwriters Laboratories Inc. is important to consumers. As an independent third-party certifier, UL has no financial interest in the product's profitability. Its not-for-profit, independent status allows UL to give an unbiased evaluation of products. This ensures that product safety standards are met, and that reasonably foreseeable risks associated with the product's usage are eliminated or mitigated. If a product carries the UL Mark, it means UL found representative samples of this product met the safety requirements of UL and all applicable codes and standards including American National Standards Institute and the National Electrical Code.

How do manufacturers and UL work together?
Most electrical products are listed by UL. All leading transfer switch manufacturers recognize the importance of designing products that meet nationally recognized standards for safety. When a manual transfer switch is developed, it is designed to meet all applicable codes and UL Standards. Engineers and designers work closely with UL Engineers to ensure that appropriate product safety requirements are identified and met. When you purchase a UL listed manual transfer switch, you are assured that an unbiased third-party certifier has fully evaluated a representative sample of that product and that it has met nationally recognized safety standards.  And that those standards are verified by quarterly product inspections.

Watch for counterfeit products and misleading labels.
The UL mark on a product consists of four distinct elements: a circle with the letters U and L; the word “LISTED�?directly beneath the circle; a product description, such as “NON-AUTOMATIC TRANSFER SWITCH;�?and a four-digit alpha/numeric code.  The four-digit code designates the manufacturing point of the product.  If any of these elements is missing, there is a chance that the product is counterfeit.

Some products do not carry a UL mark but are labeled as being “manufactured with UL listed components�?or “made with UL recognized components.�?nbsp; These words do not constitute a listing by Underwriters Laboratories Inc.  Indeed, some of these products may actually violate the National Electrical Code.


Selecting a Transfer Switch


There are a wide variety of selection criteria to be considered when choosing a residential transfer switch.




Automatic or manual system? 

There is no question that the automatic transfer switch is the ultimate in convenience and ease of operation, requiring virtually no operator intervention.  However, there is a cost for all this convenience.  Automatic systems are more expensive than manual systems; require professional installation and sometimes a larger generator requiring its own foundation and/or shelter.  Manual transfer switches require more work by the homeowner to start and connect the generator and engage the desired circuits, often during bad weather, but are less expensive and easier to install.  The selection of automatic versus manual should take into consideration factors such as:



Whole house systems usually require professional installation, as their installation generally involves the incoming utility power.


If you are unable to determine the best transfer switch for your application, contact a transfer switch manufacturer.  Some manufacturers will assist you with your specific requirements.






Tips for using portable generator


(Family Features) When a storm knocks out the power, many homeowners turn to a portable generator to keep the lights on. While portable electric generators are very useful for temporary power, they can be dangerous if used incorrectly.

The most common dangers involving generators are carbon monoxide (CO) poisoning, electrical shock or electrocution and fire hazards. The Electrical Safety Foundation International (ESFI) and Reliance Controls are warning homeowners about the hazards of improperly installing and operating portable generators.



Do not connect generators directly to your household wiring without an appropriate transfer switch being installed. A transfer switch is an electrical device that is permanently installed near the service panel in your home. It prevents the utility power and the generator power from powering your household circuits at the same time, known as backfeeding. Backfeeding can result in fires and serious injury or even death to you, utility workers or electricians working on nearby electrical systems.

“Transfer switches have been around a long time, but we find that a lot of people still don’t know what they are, or they don’t think they’re necessary,�?said Jeff Flegel, with Reliance Controls Corporation, the first company to put its user-friendly transfer switch concept on the market. “A transfer switch is easy to install, can spare a lot of heartache and is an essential safeguard to protect families and property.�?/p>

The National Electrical Code, which sets national standards intended to minimize the possibility and effects of fire and other risks, requires transfer switches be used with all portable generators in homes.

“This is the time of year when many people rely on portable generators for their homes, and many times they’re putting themselves at risk by not installing or using the generator properly,�?said Brett Brenner, President of ESFI. “People are in such a hurry to keep the lights and television on, the refrigerator running, or the basement’s sump pump operating, they don’t think about the potentially devastating consequences of hooking up a generator incorrectly.�?/p>


What is a Transfer Switch?


Any device that switches two different power sources to one load is a transfer switch. 


Transfer switches are required by the National Electrical Code (NFPA 70).  Article 702.6 states, “Transfer equipment shall be required for all standby systems subject to the provisions of this article and for which an electric-utility supply is either the normal or standby source.�?/em> 

The use of a transfer switch provides safety protection from “backfeeding�?  This is the condition that occurs when a generator or other power source is connected directly to residence wiring. The generator then supplies power through the de-energized utility wiring to the neighbors�?homes or to the utility transformer.  This inadvertently electrifies circuits and/or lines that other people believe to be “dead�?and poses significant safety hazards.  Utility workers and neighbors have been electrocuted by making contact with these “backfed�?lines.  The use of a transfer switch prevents backfeeding.

Transfer switches for residential application fall into two general categories �?automatic and manual.


An automatic transfer switch is one that transfers from the normal utility power source to the backup power source automatically, upon detection of loss of utility power, without human intervention. Automatic transfer switches are used almost exclusively with permanently and professionally installed standby generators.  


Manual transfer switches require a human operator to actually make the transfer occur.  There are three primary kinds of manual transfer switches for residential applications:

  • “Whole house�?/strong> transfer equipment consists of a transfer switching system installed between the utility meter and the main loadcenter, (an example would be a double-pole double-throw safety switch) or between the main breaker and the branch circuit breakers (an example would be a transfer panelboard).

  • “Subpanel�?/strong> transfer equipment uses a small loadcenter which contains only the branch circuits to be powered by the generator.  A separate or built-in transfer switch powers this subpanel alternately from a tap in the main panel, or from the standby generator.


  •  “Loadside�?transfer equipment uses multiple transfer switches in a single enclosure, connected after the branch circuit breaker. One switch for each circuit to be powered from the generator. 

Manual transfer switches are used almost exclusively with portable generators.






Generator sales have surged. Do you know how to help customers choose the right one?


By Rex Caldwell

I see the immediate need for the installation of home standby generators firsthand. After a natural disaster such as Hurricane Katrina, the air is filled with
noise until electricity is restored, which could be days, weeks or longer. Add to that rolling blackouts, snow, floods and ice storms, and it is easy to see why generator sales are going through the roof.


While generators can be found at most hardware stores, it does not mean that homeowners should attempt to install them. Improperly installed generators can lead to serious injuries or death to customers and electrical contractors alike.
Emphasize this to customers. In some states, electrical contractors are required by law to perform all electrical work, generator installations included. Contact your authority having jurisdiction (AHJ) for your local laws.
An overview of the types of generators and a quick refresher on installation follows.

Automatic start units

Automatic units are typically placed on a slab against one wall of the house that has no operable windows or doors. When the power goes out, there is a slight delay of 15 to 20 seconds, then the generator automatically kicks on—whether anyone is home or not—and continues running until power is restored, when it will automatically shut off. This is a great kind to suggest to older customers who might not have the ability to turn a generator on and off in the dark, or those who are not comfortable with working with electrical equipment. One downside is that automatic systems need to run once a month to verify all is in working order. Many have this function built in, however.

Normally, people want a lot of wattage with automatic units as compared to portable. Kohler, for example, has units between 8.5 and 100 kilowatts (kW). Onan has units that start at 7 and go up to 150 kW. For homeowners who want systems large enough to run the house with all appliances including central air, typically a 17 kW unit is needed. However, Kohler advertises a new 12 kW unit that can do the same.


A good feature of new standby generators is they generally have digital readout controls on output, battery voltage, oil pressure, engine hours, run conditions, system fault conditions and pass-word-secure access (Kohler offers this on units 8 to 30 kW).One big downside to automatic systems is the cost. Your customers will have to shell out $7,000 for the unit alone. Depending
on the size of the unit, when it is all said and done, customers could be dropping $10,000 or more.Make sure to ask customers where they live. If, for example, the live in a flood plain (like New Orleans), they should not opt for an automatic system. Also, an automatic generator should never be installedwhere you are susceptible to a tidal surge, such as nearby the ocean.


Portable units

You will find that most customers prefer portable generators over anything else. They are less expensive to buy (approximately $1,000 to $3,000), can be stored above flood level and moved out of danger such as when a gutter collapses during a storm.Portable power is created through a frame-mounted generator (pull start or key start) with wheels. The generator is normally stored in an outbuilding or garage. Once power goes out, the generator is retrieved, started and electrical power is transferred to the house by a heavy-duty cord. On one end is a four-prong twist-lock male plug (connecting to the generator). On the other is a female of the same connecting to a special transfer switch that separates the utility power from generator power in a way that both cannot be feeding the house at the same time or back feeding into the power lines.


Modern generators give you more

If your customer has an older generator, you may want to suggest an upgrade. In the past, generators were basic with few controls. Once started, they ran full blast until they ran out of gas or the motor seized because of lack of oil. Today’s modern portable generators, with their state-of-the-art electronic controls, can do more than just provide power. Safety controls—including one for low oil—abound. Then we get into the fancy stuff. Honda’s i-monitor series allows us to see a digital display of wattage, voltage, engine speed and hours of operation.


Installation basics

Most generator-related injuries are caused by back-feeding electricity into the provider’s system. To avoid this, install a transfer switch. When a generator is in use, a transfer switch will automatically cut off the electric connection between the electric company and household using the generator. Similarly,
it will disconnect the generator connection once power has been restored. In the past, we put the switch in its most logical place—between the meter base and the service panel. But that is no longer allowed according to the National Electrical Code (NEC). Now we have panels that connect directly into the service panel. The good news is that these panels install quickly and easily.
It has been predicted that the weather will get more unpredictable in years to come. Power outages are always a strong possibility and because of this, generator sales will continue to grow. Education is key. Providing your customers with solid knowledge on generator selection and reviewing the NEC on proper installation will help avoid accidents caused by misuse.



I had one customer who bought three generators before he got the correct one. The first one didn’t have enough wattage and the second one didn’t have the right voltage (it was 240 only, not 120/240). It can be confusing, even to a professional. But, if you provide your customers with some basic tips, it may cut down the number of generators they have to choose from. Some tips are as follows:


        • The most important thing to ask customers is where the generator is to be placed.Stress that they never run a generator in the garage. The deadly exhaust fumes go right into the house. Placing the generator away from the house by a few feet (preferably downwind) can lower the noise and perhaps save a life.
        • A portable generator must have 120/240 on a single four-prong twist-lock female outlet. Customers should not buy a 240 or 120-volt only generator. While common 120-volt receptacles are nice to have for some portable appliances, 120/240 is required to run the house.
        • Ask customers to figure the highest maximum wattage they think they need and tell them to get one higher.
        • How big is the customer’s tank The customer will need a tank large enough (around six gallons or more) to avoid constantly filling the generator. The customer will also need a tank fuel fill gauge to see how much gasoline is left in the tank without having to pull the cap and stare into the tank. Do they have one?
        • Does the customer go out of town often? If so, an automatic generator may be the way to go. However, they aren’t foolproof. You may want to suggest PhoneAlert, a monitoring system from Reliance Controls Corp. If, for whatever reason, the automatic generator fails to start and you are not home, the system will call you and let you know about the problem. This is helpful for those with manual generators. Once the power goes out, the system will call you, so you can come home and turn the generator on or have someone
          do it for you if you are unable to get there.

        Reprinted with permission from ELECTRICAL CONTRACTOR magazine.