Portable Generator Transfer Switch


A portable generator transfer switch lets you run all of the appliances hardwired to your home during a power outage. Find out how they work and what kinds to look for.

This is a Reliance Controls portable generator transfer switch good for generators up to 7,500 watts.

If you already have a portable generator or are thinking about buying one then you should definitely consider getting a transfer switch installed as well. With a switch you’ll be able to run all of your hardwired appliances like your central air conditioning, electrical wall sockets, and furnace during a blackout. Plus you won’t need to worry about having to run multiple long extension cords out of your home to your generator. You’ll be able to simply plug any appliances you need into your wall sockets and operate them just as if the main power was still on. Automatic transfer switches will even turn on automatically within 20 to 30 seconds after the main power goes out, without you having to do a thing.

Simply speaking, a portable generator transfer switch is a device that switches the power supply from the main source to a backup, portable generator. Most people rely on one source of power to run the utilities, in most cases this main power comes from government or privately operated sources of power (like windmills, nuclear power plants, hydro-power etc). However, many people install a secondary power supply to act as a backup for important features, such as security systems, garage door openers, computers or even just a few lights. This is a very useful piece of equipment to have if you live in an area which has somewhat frequent power outages (as a result of storms or bad weather). A generator transfer switch changes the power supply from the main source to the small generator.

Types of Transfer Switches

There are two main types of power transfer switches; automatic and manual. There are also combinations of manual and automatic. A manual transfer switch (MTS) is less expensive, and requires someone to manually flip a switch to change the power source. These are usually used in residential homes to run basic operations, and can be used with portable or stationary generators. Automatic transfer switches (ATS) are more expensive and make the switch to generator power automatically. An ATS can also start the generator, based upon a pre-determined schedule, typically monthly or weekly, to make sure it is operating properly and perform basic maintenance checks on your machine.

How Portable Generator Transfer Switches Work

Automatic transfer switches will immediately sense a break in the power supply and start the generator typically within 20 to 30 seconds after the main power goes out. Once the generator is running, it will then switch the supply to the generator. When the main power supply is restored and starts giving power at the correct (pre-determined) voltage, it will then switch back to the main source and shut off the generator. It does this after several minutes to ensure that the main power has been restored fully and won’t be flickering on and off.


With a manual transfer switch, you’ll need to go outside, turn the generator on, make sure it’s running at a proper speed and flip the transfer switch. Both ATS and MTS switches work on what is known as a “break-before-make” policy, which requires the first connection to be broken before the new one is made. An MTS switch for a small or portable generator will have three positions, LINE (Main Source), OFF (No Connection) and GEN (Generator).

Why You Need A Transfer Switch

Without a transfer switch you have to plug extension cords into your generator and run them into your home to power the appliances you want to use. If you only plan to use a few items this is not a problem. But if you want to use multiple appliances and the weather is really cold and nasty out then the last thing you want to be doing is trying to run extension cords back and forth. This is even more of a hassle at night. Using a transfer switch is just a huge convenience; you simply plug your appliances into the wall outlet just as you would normally with the main power on.

You can’t plug your generator into your main home power yourself without a transfer switch because it will cause back feed. Backfeeding is when an alternative power source feeds the main lines (leading to the main power grid) with electricity. This is a serious hazard which can lead to shorts, explosions or even electrocuting linemen, who are trying to repair wires which they think are dead but are in fact live.

Connecting a portable generator transfer switch is not an easy business, which is why the switch installation has to be certified. Having a noncertified transfer switch in your home is an offense which can result in a fine or other legal action in some states. Another reason, besides the obvious safety reasons, is that failure to install a legal transfer switch can result in your home owner’s insurance policy being cancelled.

I recommend using a licensed electrician to install your generator transfer switch. Parts and installation for a manual switch will run you around $500 to $600. For an automatic switch around $1,000.

What to Look For When Buying a Transfer Switch

Transfer switches do not come in one-size-fits-all models, each generator needs a transfer switch that matches the voltage output so that no shorting or overloading occurs. Depending on building codes in your state, you may need a switch that can be hardwired (built into the house), or simply strung like a cord. Each transfer switch has a maximum wattage and combined load, which should be matched exactly to the generator that it is being used.

You’ll also need to look at how many circuits you want to power. With a 5,000 watt generator you’ll be able to hook up at least five circuits. With a more powerful generator you can add more circuits. Most transfer switches already have circuit breakers built into them and you can easily select the number and type you want to match your home’s circuit breakers.

When your electrician installs your transfer switch he can use a mounting kit to place it down into the wall in between the studs in the drywall. This is a seamless and attractive approach. The other option is to simply hang it on the wall like a picture, which I wouldn’t really recommend.

The following is an informative video on Gen-Tran transfer switches, which are very popular and highly rated.

If you want to search for different portable generator transfer switchmodels just click the link. Surprisingly Amazon.com has dozens of high quality transfer switches available for very economical prices.

Safety Precautions

It is absolutely necessary that any cords, wires and switches that you buy are UL listed (Underwriters Lab – an independent safety certification). If you are unsure about the specifications required, you should contact your manufacturer or a reputable vendor.

Installing the switch and making sure it is connected properly is not recommended as a do-it-yourself job, unless you already have a thorough knowledge of electricity and experience with similar jobs. The safest and best choice is to get a certified electrician to install all the wires. If you follow the above precautions and make sure to consult your manuals and an electrician if you don’t have the experience yourself, your portable generator will run safely without problems.


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