With increasing severe weather events around the world, more and more people are becoming interested in having a back up power source for their home in case of a power outage. If you are one of them, then the concept of the transfer switch is one that you should familiarize yourself with.
A transfer switch allows you to select between two power sources from which to provide electricity to your home – say, the power grid that usually keeps the lights on and a back up power source, like a portable generator, that can help you get the lights back on if the primary power source goes down. This device can make that switch easier and safer.
This article will explain how a transfer switch works, how it can be helpful to you, the pros and cons of different types, and the guidelines that must be followed to stay safe and within the limits of the law. A careful reading will leave you better prepared to acquire the appropriate transfer switch and ensure that it is installed correctly.
How Does a Transfer Switch Work?
A transfer switch, which allows you to choose between two electrical sources, is typically installed near the electrical service panel box, also sometimes called the fuse box or circuit breaker panel and usually located in the basement, garage, or some other out of the way place. The transfer switch is installed here because the electrical service panel is where external electrical wires from the power grid connect to the internal wires of your home’s electrical system.
It makes sense, then, that this would be the place where you would be able to switch to another power source – such as a generator – for the entire house. And having the switch here eliminates the need to run extension cords from an outdoor portable generator inside to various appliances; electricity for indoor appliances runs through the same wires that it normally does.
Is It Necessary to Have a Transfer Switch for My Generator?
Physically speaking, it is possible to run indoor appliances off of a portable generator without a transfer switch, but that doesn’t mean that it’s a good idea. Here are a few reasons why you should install a transfer switch if you plan to use a generator as a back up power source for your home:
The National Electric Code (NEC) requires you to. In case of use of a generator to provide electricity to your home, having a safely installed transfer switch is required under NEC regulations 700.5 and 701.5 for the use of a back up power source to support an emergency electrical load. Compliance with the NEC becomes even more important if you intend to sell your home in the future – improper installation could reduce the house’s sale price.
Having a transfer switch makes powering your home during an outage much easier. Many of your most essential appliances, like your water heater, furnace fan, and central air conditioner, are wired directly into your home’s electrical system, and can not simply be plugged in to another power source. Not to mention the headache you’ll save yourself by avoiding the task of untangling and setting up extension cords in the dark…
Not having a transfer switch and using a portable generator could lead to backfeeding, which is potentially hazardous. Backfeeding occurs when electrical current flows in the opposite direction as originally intended – in the case of your house, that means electricity flowing from the portable generator, through your internal wiring, and out into the external service lines. This scenario presents a serious danger to those working to restore power lines who may not be aware of a backfeed. A transfer switch isolates your home from the power grid when the secondary power source is selected, ensuring that backfeeding does not happen.
Finding the Right Transfer Switch
There are a number of different transfer switches with different features out there, and knowing which one is right for you can be tough. Here’s a breakdown of the options to help making choosing a little bit easier:
There are two main classes of transfer switches: automatic transfer switches and manual transfer switches.
Manual transfer switches, as you probably guessed, require you to go to the electrical service panel and physically flip the switch in order to toggle between power sources. Until the switch is flipped, household appliances including refrigerators, air conditioners and water heaters will remain without power. They are relatively simple devices and, unsurprisingly, less expensive than automatic ones.
An automatic transfer switch (ATS) switches to the secondary power source as soon as it registers the loss of voltage usually associated with a power outage and causes the backup generator to kick in. Once the power comes back on, they switch back to the primary power source and tell the generator to turn off. Although most commonly used with a home standby generator, an ATS can function with a portable generator equipped with an electric starter.
What Should You Look for in an Automatic Transfer Switch?
There are four different types of ATS:
Open transition – also known as a “break before make” switch, this type breaks its connection with the first power source before connecting to the second, which means that the current will be briefly interrupted when the switch is made.
Closed transition – sometimes referred to as a “make before break” transfer switch, this type of switch can connect to the second power source before disconnecting to the first, provided that the two power sources have similar voltages, frequencies and phase angles.
Center off – usually used with sizeable inductive loads and similar to closed transition, this type of switch lets magnetic fields collapse before connecting to the second power source.
Solid state – this type uses a transistor to make an extremely quick switch, thanks to a lack of moving parts. This can be important for sensitive equipment which might be damaged by interruptions of electrical flow, making it probably the most desirable type of ATS.
Your automatic transfer switch should be designed to handle your house’s total system load and rated for the voltage that running your electrical systems will require. The amount of amperage that it is rated to handle should match that of the main circuit breaker if you opt for a service disconnect switch (see below).
Types of Automatic Transfer Switch
There are three main types of transfer switch, each with their own purpose and advantages.
Load center transfer switches are intended to handle 8 to 16 essential circuits in the electrical service panel. They make sense when you’ll be using your generator only to run must have appliances, rather than the entire house. They may cost less up front, but are more complicated to install because they only power select circuits.
Service disconnect switches power the entire electrical service panel, which works if your generator will be able to power your entire household. They tend to be more costly but simpler to install.
Standard switches will power only one particular subpanel. They are rarely used in the present day.
Transfer switches can be purchased pre-wired or connected to a power inlet box. A pre-wired transfer switch already has the wiring necessary for connection to the electrical service panel. It is only necessary to connect the switch’s conduit to the fuse box, thread the wires through that conduit and connect the wires from the transfer switch to the circuit breakers on the electrical panel that correspond to the circuits that the generator will power.
A power inlet box is usually mounted on an exterior wall of the house. It provides a hard-wired connection from the outside of the house, where the generator will be, to the transfer switch near the electrical service panel. With an inlet box, there is no need to run an extension cord out a window.
Occasionally, transfer switches may be mounted outside, as close to the electrical service panel as is feasible, and necessarily protected by a waterproof cover.
It will likely be necessary to solicit the services of a licensed electrician to install a transfer switch. Do not hesitate to do so if you have any doubts.
Frequently Asked Questions
Is a permit required for a transfer switch installation?
Normally it is, since any permanent addition to your home must be validated by the local governing body. If you hire a professional electrician, they should be familiar with the permit process and able to solicit one for you.
How much will it cost to hire an electrician to install a transfer switch?
That will depend where you live and the complexity of the job in your house. A ballpark estimate would be for three to four hours of work and a bill of as much as $500. You can minimize electrician’s fees by choosing a widely recognized transfer switch, like those manufactured by Reliance Control, that the electrician will likely be familiar with.
How far away should the generator be from your transfer switch?
There is no fixed distance prescribed. As long as your generator is at least 20 feet from your house and you have a long enough extension cord, you should be fine.